There is no doubt that “infection”, “infectious process” and “infectious disease” are in a certain way associated with pathogenic microbes and at the same time with a macroorganism (human, animal, etc.). It can be noted that pathogenic microbes located in the external environment are not yet an infection, because they can significantly change their metabolism and lose some of the pathogenic factors (spores). The microflora of the human body, which does not cause a pathological process, is also not an infection, and quite mutually beneficial processes often “begin” between it and the body.
The term “infection” in translation means “I infect”, “I pollute” and is more closely associated with pathogenic microorganisms that are not in a dormant state or outside the human body, but in opposition to the macroorganism. Pathogenic microorganisms do not interact with the human body, and both of these sides, being in opposition, try to break each other’s resistance.
Thus, infection is a generalized term indicating microorganisms that exhibit their inherent degree of pathogenicity in a susceptible human body and cause an infectious process, the highest form of manifestation of which is an infectious disease.
This reflects the essence of the infectious process and infectious disease, as well as the factors involved in them. This fully corresponds to the term “source of infection” in relation to patients with an obvious or latent infectious process, who release pathogenic microbes into the external environment that, through a wide variety of contacts, can cause this disease in other susceptible people.
Known different variants infection of people with an infectious principle, which is determined for various reasons:
1. Superinfection- layering of repeated infection, which can again cause an infectious disease of identical etiology in a sick person. This option is possible in the absence of immunity (gonorrhea and other infections)
2. Reinfection- layering of repeated infection, which causes an infectious disease of identical etiology in the person who has been ill. The option is similar to the previous one.
3. Secondary infection- layering of a new infection, which causes the patient to develop a disease of a different etiology against the background of a primary infectious disease.
4. Autoinfection- this is one’s own infection (formerly opportunistic, opportunistic microflora), which caused an infectious disease in a weakened person (hypothermia, vitamin deficiency, acute and chronic diseases, stress, etc.).
5. Mixed infections- these are polyinfections that cause a polyetiological infectious disease in a susceptible person.
6. Monoinfection– an infection of one species that causes in a susceptible person a monoinfectious disease characteristic of that species.
By origin, the infection can be exogenous or endogenous.
Exogenous infection- these are pathogenic microbes that have penetrated into a susceptible organism from the external environment (soil, water, food, toys, hands, air, medications, etc.), through numerous factors and routes of infection..
Endogenous infection- this is the microflora of the human body, which he normally does not notice, but it can cause certain infectious diseases when the body’s defenses are weakened, the skin and mucous membranes are damaged, etc.
If the name of a disease or type of bacteria is added to the term “infection,” then a more specific infectious agent or causative agent of an infectious disease or group of such diseases will appear, for example, intestinal infection, typhoid infection, etc.
The process of infection entering the body of a susceptible person, in general, can be described as infection, i.e. a process that combines stages referred to as adhesion, colonization and invasion. If pathogenic microorganisms enter environmental objects and contaminate them, then this process is called microbial contamination or contamination.
The infectious process is a complex of multi-level and multi-system internal processes, including pathological ones, occurring in the body in response to the pathogenic effects of infection. The accumulation of internal processes often turns into pathology, which is manifested by manifest (external) signs. This indicates the occurrence of an infectious disease. It happens that internal processes, reflecting the degree of the body’s resistance to infection, do not develop into a manifest form, although the duration of the internal process can be significant (for example, persistence, etc.).
Thus, an infectious disease is a manifest manifestation of an infectious process occurring in the body in response to the pathogenic effects of an infection, which can be exogenous or endogenous in origin.
In connection with the predominant disease of people or animals, the following main groups of infectious diseases are distinguished:
n anthroponotic(mostly people are sick, for example, cholera, typhoid fever, gonorrhea, etc.),
n zoonotic(mainly animals are sick, for example, swine fever, chicken cholera, infectious anemia of horses, etc.),
n anthropozoonotic(people and animals are sick, for example, tularemia, leptospirosis, plague, brucellosis, etc.).
At the same time, such gradations are quite arbitrary, generated by the level of knowledge of modern science. For example, shigellosis (dysentery) for a long time were considered an anthroponotic disease, but at present significant data have accumulated on the disease of shigellosis in cows, pigs and other animals and birds with a clinical picture and the isolation of Shigella. Some types of viruses that previously affected monkeys now cause diseases in humans (HIV, Ebola, etc.).
INFECTIOUS PROCESS AND INFECTIOUS DISEASES
The penetration of microorganisms into the internal environment of the human body leads to a disruption of the body’s homeostasis, which can manifest itself as a complex of physiological (adaptive) and pathological reactions known as infectious process, or infection. The spectrum of these reactions is quite wide, its extreme poles being clinically pronounced lesions and asymptomatic circulation. The term "infection" (from Lat. inficio- introduce anything harmful and it’s too late. infectio- infection) can be determined by the infectious agent itself and the fact of its entry into the body, but it is more correct to use this term to denote the entire set of reactions between the pathogen and the host.
According to I.I. Mechnikov, “...infection is a struggle between two organisms.” Domestic virologist V.D. Soloviev considered the infectious process as “a special kind of ecological explosion with a sharp increase in interspecific struggle between the host organism and the pathogenic bacteria that have penetrated into it.” Famous infectious disease specialists A.F. Bilibin and G.P. Rudnev (1962) defined it as a complex set of “physiological protective and pathological reactions that occur under certain environmental conditions in response to the influence of pathogenic microbes.”
The modern scientific definition of the infectious process was given by V.I. Pokrovsky: “The infectious process is a complex of mutual adaptive reactions in response to the introduction and reproduction of a pathogenic microorganism in a macroorganism, aimed at restoring disturbed homeostasis and biological balance with the environment.”
Thus, the participants in the infectious process are the microorganism that causes the disease, the host organism (human or animal) and certain, including social, environmental conditions.
Microorganism represents the direct cause of an infectious disease, determines the specificity of its clinical manifestations, and influences the course and outcome of the disease. Its main specific qualities:
Pathogenicity;
Virulence;
Toxigenicity;
Adhesiveness;
Pathogenicity is the ability of a pathogen to penetrate the human or animal body, live and reproduce in it, causing morphological and functional
Toxigenicity of the pathogen is the ability to synthesize and secrete exo- and endotoxins. Exotoxins are proteins released by microorganisms during their life processes. They exhibit a specific effect, leading to selective pathomorphological and pathophysiological disorders in organs and tissues (pathogens of diphtheria, tetanus, botulism, cholera, etc.). Endotoxins are released after the death and destruction of the microbial cell. Bacterial endotoxins - structural components the outer membrane of almost all gram-negative microorganisms, biochemically representing a lipopolysaccharide complex (LPS complex). Structural and functional analysis of the LPS complex molecule showed that the biologically active site (site) that determines all the main properties of the native preparation of the LPS complex is lipid A. It is characterized by pronounced heterogeneity, which allows the body’s defenses to recognize it. The action of endotoxins is non-specific, which is manifested by similar clinical signs of the disease.
Adhesiveness and invasiveness of microorganisms - the ability to fix on cell membranes and penetrate cells and tissues. These processes are facilitated by ligand-receptor structures and capsules of pathogens, which prevent absorption by phagocytes, as well as flagella and enzymes that damage cell membranes.
One of the most important mechanisms for preserving the pathogen in the host body is microbial persistence, which consists in the formation of atypical wallless forms of the microorganism - L-forms, or filterable forms. In this case, a sharp restructuring of metabolic processes is observed, expressed in a slowdown or complete loss enzymatic functions, inability to grow on selective nutrient media for the original cellular structures, loss of sensitivity to antibiotics.
Virulence is a qualitative manifestation of pathogenicity. The sign is unstable; for the same strain of pathogen it can change during the infectious process, including under the influence of antimicrobial treatment. Under certain characteristics of the macroorganism (immunodeficiency, violation of barrier protective mechanisms) and environmental conditions, opportunistic microorganisms and even saprophytes can become culprits in the development of an infectious disease.
The place where a pathogenic pathogen enters the human body is called the entry gate of infection; the clinical picture of the disease often depends on its location. The properties of the microorganism and the route of its transmission determine the variety of entry gates.
They may be:
Skin (for example, for pathogens of typhus, plague, anthrax, malaria);
Mucous membranes respiratory tract(in particular, for influenza virus and meningococcus);
Gastrointestinal tract (for example, for pathogens of typhoid fever, dysentery);
Genital organs (for pathogens of syphilis, HIV infection, gonorrhea).
For various infectious diseases there may be one (cholera, influenza) or several (brucellosis, tularemia, plague) entrance gates. The formation of the infectious process and the severity of the clinical manifestations of the infectious disease are significantly influenced by the infecting dose of pathogens.
From the entrance gate, the pathogen can disseminate predominantly through the lymphogenous or hematogenous route.
When the pathogen is in the blood and lymph, the following terms are used:
-bacteremia(presence of bacteria in the blood);
-fungemia(presence of fungi in the blood);
-viremia(viruses in the blood);
The circulation of microbial toxins is defined by the term toxinemia. In some infectious diseases, bacteremia and toxinemia are observed simultaneously (for example, in typhoid fever, meningococcal infection), while in others, predominantly toxinemia develops (dysentery, diphtheria, botulism, tetanus). Disseminating in the human body, pathogens can affect various systems, organs, tissues and even individual types of cells, i.e. show a certain selectivity, tropism. For example, influenza viruses are tropic to the epithelium of the respiratory tract, pathogens of dysentery - to the intestinal epithelium, and malaria - to erythrocytes.
The macroorganism is an active participant in the infectious process, determining the possibility of its occurrence, form of manifestation, severity, duration and outcome. The human body has a variety of innate or individually acquired factors of protection against the aggression of pathogenic pathogens. The protective factors of the macroorganism help to prevent an infectious disease, and if it develops, to overcome the infectious process. They are divided into nonspecific and specific.
Nonspecific protective factors are very numerous and diverse in their mechanisms of antimicrobial action. External mechanical barriers
the basis for most microorganisms is intact skin and mucous membranes.
The protective properties of the skin and mucous membranes are provided by:
Lysozyme;
Secrets of the sebaceous and sweat glands;
Secretory IgA;
Phagocytic cells;
Normal microflora that prevents intervention and colonization of the skin and mucous membranes by pathogenic microorganisms.
An extremely important barrier to intestinal infections is the acidic environment of the stomach. The mechanical removal of pathogens from the body is facilitated by the cilia of the respiratory epithelium and the motility of the small and large intestines. The blood-brain barrier serves as a powerful internal barrier to the penetration of microorganisms into the central nervous system.
Nonspecific inhibitors of microorganisms include enzymes of the gastrointestinal tract, blood and other biological fluids of the body (bacteriolysins, lysozyme, properdin, hydrolases, etc.), as well as many biologically active substances [IFN, lymphokines, prostaglandins (PG), etc.].
Following external barriers, the universal forms of defense of the macroorganism are phagocytic cells and the complement system. They serve as links between nonspecific protective factors and specific immune responses. Phagocytes, represented by granulocytes and cells of the macrophage-monocyte system, not only absorb and destroy microorganisms, but also present microbial Ags to immunocompetent cells, initiating an immune response. Components of the complement system, attaching to AT molecules, provide their lysing effect on cells containing the corresponding Ag.
The most important mechanism for protecting the macroorganism from the effects of a pathogenic pathogen is the formation of immunity as a complex of humoral and cellular reactions that determine the immune response. Immunity determines the course and outcome of the infectious process, serving as one of the leading mechanisms maintaining the homeostasis of the human body.
Humoral reactions are caused by the activity of antibodies synthesized in response to the penetration of antigens.
AT are represented by immunoglobulins of various classes:
-IgM;
-IgG;
-IgA;
-IgD;
-IgE.
In the most early stage immune response are the first to form IgM as phylogenetically the most ancient. They are active against many bacteria, especially in agglutination (RA) and lysis reactions. Significant titles IgG appear on the 7-8th day after the action of the antigenic stimulus. However, upon repeated exposure to Ag, they are formed already on the 2-3rd day, which is due to the formation of immunological memory cells in the dynamics of the primary immune response. In a secondary immune response, the titer IgG significantly exceeds the titer IgM. In the form of monomers IgA circulate in the blood and tissue fluids, but dimers are of particular importance IgA, responsible for immune
reactions on the mucous membranes, where they neutralize microorganisms and their toxins. Therefore they are also called secretory AT, since they are mainly found not in blood serum, but in the secretions of the gastrointestinal tract, respiratory and reproductive tracts. They play a particularly important role in intestinal infections and acute respiratory viral infections. Protective functions IgD And IgE have not been fully studied. It is known that IgE participates in the development of allergic reactions.
The specificity of antibodies is due to their strict compliance with the antibodies of the pathogen that caused their formation and interaction with them. However, Abs can also react with Ags from other microorganisms that have similar antigenic structure(common antigenic determinants).
In contrast to humoral reactions realized through circulating antibodies in the body, cellular immune reactions are realized through the direct participation of immunocompetent cells.
The regulation of the immune response is carried out at the genetic level (immunoreactivity genes).
Environment how the 3rd component of the infectious process affects its occurrence and the nature of its course, affecting both the micro- and macroorganism. Temperature, humidity and dustiness of the air, solar radiation, antagonism of microorganisms and other numerous natural environmental factors determine the viability of pathogenic pathogens and influence the reactivity of the macroorganism, reducing its resistance to many infections.
Social environmental factors influencing the development of the infectious process are extremely important:
Deterioration of the environmental situation and living conditions of the population;
Poor nutrition;
Stressful situations due to socio-economic and military conflicts;
State of health;
Availability of qualified medical care etc. Forms of the infectious process may vary depending on
properties of the pathogen, conditions of infection and the initial state of the macroorganism. To date, not all of them have been sufficiently studied and clearly characterized. The main forms of the infectious process can be presented in the following table (Table 2-1).
Table 2-1. The main forms of the infectious process
Transitional(asymptomatic, healthy) carrier status- a single (accidental) detection of a pathogenic (or any other) microorganism in the human body in tissues considered sterile (for example, in the blood). The fact of transient carriage is determined in a series of successive bacteria
theriological analyses. At the same time, currently existing examination methods do not allow identifying clinical, pathomorphological and laboratory signs of the disease.
Carriage of pathogenic microorganisms is possible during the stage of recovery from an infectious disease (convalescent carriage). It is typical for a number of viral and bacterial infections. Depending on the duration, convalescent carriage is divided into acute(up to 3 months after clinical recovery) and chronic(over 3 months). In these cases, carriage is asymptomatic or occasionally manifests itself at a subclinical level, but may be accompanied by the formation of functional and morphological changes in the body, and the development of immune reactions.
Inapparent infection- one of the forms of the infectious process, characterized by the absence of clinical manifestations of the disease, but accompanied by an increase in titers of specific antibodies as a result of the development of immune reactions to the pathogen's Ag.
Manifest forms The infectious process constitutes a broad group of infectious diseases caused by exposure of the human body to various microorganisms - bacteria, viruses, protozoa and fungi. For the development of an infectious disease, the introduction of a pathogenic pathogen into the human body is not enough. The macroorganism must be susceptible to this infection, respond to the influence of the pathogen by developing pathophysiological, morphological, protective-adaptive and compensatory reactions that determine the clinical and other manifestations of the disease. At the same time, micro- and macroorganisms interact in certain, including socio-economic, environmental conditions, which inevitably influence the course of the infectious disease.
The division of diseases into infectious and non-infectious is quite arbitrary.
Basically, it is traditionally based on two criteria characteristic of the infectious process:
Presence of a pathogen;
Contagiousness (infectiousness) of the disease.
But at the same time, the obligatory combination of these criteria is not always observed. For example, the causative agent of erysipelas - β-hemolytic streptococcus of group A - also causes the development of non-contagious glomerulonephritis, dermatitis, rheumatic process and other diseases, and erysipelas itself, as one of the forms of streptococcal infection, is considered practically non-contagious. Therefore, not only infectious disease specialists, but also representatives of almost all clinical specialties are faced with the treatment of infectious diseases. Apparently, most human diseases could be classified as infectious. The creation of an infectious disease service, which historically developed as a result of the development of specialization in medicine, is intended to provide qualified care to infectious patients at the pre-hospital (at home), hospital (in hospital) and dispensary (observation after discharge from hospital) stages.
The nature, activity and duration of clinical manifestations of an infectious disease, which determine the degree of its severity, can be extremely diverse.
With a typical overt infection, the clinical signs and general features characteristic of an infectious disease are clearly expressed:
Sequence of changing periods;
The possibility of developing exacerbations, relapses and complications, acute, fulminant (fulminant), protracted and chronic forms;
Formation of immunity.
The severity of manifest infections may vary:
Light;
Average;
Heavy.
A special form of diseases known as slow infections cause prions.
They are characterized by:
Many months or even many years incubation period;
Slow but steadily progressive course;
A complex of peculiar lesions of individual organs and systems;
Development of oncological pathology;
Inevitable death.
Atypical manifest infections can occur as erased, latent and mixed infections. An erased (subclinical) infection is a variant of the manifest form, in which the clinical signs of the disease and the change in its periods are not clearly expressed, often minimally, and the immunological reactions are incomplete. Diagnosis of an erased infection causes significant difficulties, which contributes to the prolongation of the infectious disease due to the lack of timely, comprehensive treatment.
The simultaneous occurrence of two infectious diseases caused by different pathogens is possible. In such cases, they speak of a mixed infection, or mixed infection.
The development of an infectious disease can be caused by the dissemination of pathogenic pathogens that were previously in the human body in the form of a dormant latent focus of infection, or by the activation of opportunistic and even normal flora inhabiting the skin and mucous membranes. Such diseases are known as endogenous infections(autoinfections).
As a rule, they develop against the background of immunodeficiencies associated with various reasons:
Severe somatic diseases;
Surgical interventions;
The use of toxic medicinal compounds, radiation and hormonal treatment;
HIV infection.
It is possible to be re-infected with the same pathogen with subsequent development of the disease (usually in a manifest form). If such infection occurs after the end of the primary infectious process, it is defined as reinfection. It is necessary to distinguish from reinfections and, especially, mixed infections superinfections, arising when infected with a new infectious agent against the background of an existing infectious disease.
GENERAL FEATURES OF INFECTIOUS DISEASES
The generally accepted term “infectious diseases” was introduced by the German physician Christoph Wilhelm Hufeland.
Main signs of infectious diseases:
A specific pathogen as the direct cause of the disease;
Contagiousness (infectiousness) or the occurrence of several (many) diseases caused by a common source of infection;
Often prone to widespread epidemic spread;
Cyclicity of the course (consecutive change of periods of illness);
Possibility of developing exacerbations and relapses, protracted and chronic forms;
Development of immune reactions to pathogen Ag;
Possibility of developing carriage of the pathogen. Pathogens
Specific pathogens of infectious diseases can be:
Bacteria;
Rickettsia;
Chlamydia;
Mycoplasmas;
Mushrooms;
Viruses;
Prions.
The higher the contagiousness of the disease, the greater its tendency to widespread epidemic spread. Diseases with the most pronounced contagiousness, characterized by severe course and high mortality, are combined into a group of especially dangerous infections.
Such diseases include:
Plague;
Cholera;
Yellow fever;
Lassa, Ebola, Marburg fevers.
Cyclicity of the flow characteristic of most infectious diseases. It is expressed in a sequential change of certain periods of the disease:
Incubation (hidden);
Prodromal (initial);
The period of main manifestations (the height of the disease);
Fading of symptoms (early convalescence);
Recovery (reconvalescence).
Incubation period
The hidden period of time between the moment of infection (penetration of the pathogen into the body) and the appearance of the first clinical symptoms of the disease. The duration of the incubation period varies for different infections and even for individual patients with the same infectious disease.
The duration of this period depends on:
On the virulence of the pathogen and its infectious dose;
Localization of entrance gates;
The state of the human body before the disease, its immune status.
Determining the duration of quarantine, carrying out preventive measures and solving many other epidemiological issues are carried out taking into account the duration of the incubation period of the infectious disease.
Prodromal (initial) period
Usually the illness lasts no more than 1-2 days; it is not observed with all infections.
In the prodromal period, the clinical signs of the disease do not have clear specific manifestations and are often the same for different diseases:
Increased body temperature;
Headache;
Myalgia;
Arthralgia;
Malaise;
Brokenness;
Decreased appetite, etc.
The period of the main manifestations (height) of the disease
This period is characterized by the appearance and (often) increase in the most characteristic clinical and laboratory signs specific to a particular infectious disease. The degree of their severity is maximum in manifest forms of infection.
By assessing these signs you can:
Make the correct diagnosis;
Assess the severity of the disease;
Guess the nearest forecast;
Prevent the development of emergency conditions.
The different diagnostic significance of symptoms allows us to divide them into decisive, supporting and guiding.
. Decisive symptoms characteristic specifically for a specific infectious disease (for example, Filatov-Koplik-Belsky spots in measles, hemorrhagic star-shaped rash with elements of necrosis in meningococcemia).
. Reference symptoms are typical for this disease, but they can also be found in some others (jaundice with viral hepatitis, meningeal symptoms with meningitis, etc.).
. Suggestive symptoms less specific and similar for a number of infectious diseases (fever, headache, chills, etc.).
Period of fading of symptoms (early convalescence)
Follows the peak period with a favorable course of the infectious disease. Characterized by the gradual disappearance of the main symptoms.
One of its first manifestations is a decrease in body temperature. It can occur quickly, within a few hours (crisis), or gradually, over several days of illness (lysis).
Recovery period (reconvalescence)
Develops after the extinction of the main clinical symptoms. Clinical recovery almost always occurs before the morphological abnormalities caused by the disease completely disappear.
In each specific case, the duration of the last two periods of the infectious disease is different, which depends on many reasons:
Forms of the disease and its severity;
The effectiveness of the treatment;
Features of the immunological response of the patient’s body, etc.
With complete recovery, all functions impaired as a result of the infectious disease are restored; with incomplete recovery, certain residual effects remain.
In many infectious diseases there is also the possibility of developing exacerbations and relapses, protracted and chronic forms. The causes of these conditions are varied and not well understood.
They may be associated with specific features of all three components of the infectious process:
Pathogen;
Macroorganism;
Environmental conditions.
Each patient has individual characteristics of the course of the infectious disease.
They may be due to:
The previous physiological state of the most important organs and systems (premorbid background) of the patient;
The nature of nutrition;
Features of the formation of nonspecific and specific protective reactions;
A history of vaccinations, etc.
The state of the macroorganism and, consequently, the course of the infectious disease is influenced by numerous environmental factors:
Temperature;
Humidity;
Radiation level, etc.
Of particular importance is the influence of social factors on the development of an infectious disease in humans:
Population migration;
Nutritional pattern;
Stressful situations, etc.
Aspects of the deteriorating environmental situation have an adverse effect on the macroorganism:
Radiation;
Gas pollution;
Carcinogenic substances, etc.
The deterioration of the external environment, most noticeable in recent decades, has an active influence on the variability of microorganisms, as well as on the formation of an unfavorable premorbid background in humans (in particular, immunodeficiency states). As a result, the typical clinical picture and course of many infectious diseases change significantly.
The following concepts have taken root in the practice of infectious disease doctors:
Classical and modern course of infectious disease;
Atypical, abortive, erased forms;
Exacerbations and relapses.
Atypical forms of an infectious disease are considered to be conditions characterized by the dominance in its clinical manifestations of signs that are not characteristic of the disease, or the absence of typical symptoms. For example, the predominance of meningeal symptoms (meningotif) or the absence of roseola exanthema in typhoid fever. Atypical forms also include the abortive course, characterized by the disappearance of clinical manifestations of the disease without the development of its typical signs. When the course of the disease is erased, there are no characteristic symptoms, and general clinical manifestations weakly expressed and short-lived.
An exacerbation of an infectious disease is considered to be a repeated deterioration in the general condition of the patient with an increase in the characteristic clinical signs of the disease after they have weakened or disappeared. If the main pathognomonic signs of the disease develop again in the patient after the clinical manifestations of the disease have completely disappeared, they speak of its relapse.
In addition to exacerbations and relapses, during any period of an infectious disease it is possible development of complications. They are conventionally divided into specific (pathogenetically related to the underlying disease) and nonspecific.
The culprit of specific complications is the causative agent of this infectious disease. They develop due to unusual severity of typical clinical and morphological manifestations of the disease (for example, acute hepatic encephalopathy in viral hepatitis, perforation of ileal ulcers in typhoid fever) or due to atypical localizations of tissue damage (for example, endocarditis or arthritis in salmonellosis).
Complications caused by microorganisms of another type (for example, bacterial pneumonia with influenza) are considered nonspecific.
The most dangerous complications of infectious diseases:
Infectious toxic shock (ITSH);
Acute hepatic encephalopathy;
Acute renal failure (ARF);
Brain swelling;
Pulmonary edema;
Hypovolemic, hemorrhagic and anaphylactic shock.
They are discussed in the relevant chapters of the special part of the textbook.
Many infectious diseases are characterized by the possibility of developing microbial carriage. Carriage is a unique form of infectious process in which the macroorganism, after the intervention of the pathogen, is not able to completely eliminate it, and the microorganism is no longer able to maintain the activity of the infectious disease. The mechanisms of carrier development have not been sufficiently studied to date; methods for effective rehabilitation of chronic carriers have not yet been developed in most cases. It is assumed that the basis for the formation of carriage is a change in immune reactions, in which selective tolerance of immunocompetent cells to pathogen Ags and the inability of mononuclear phagocytes to complete phagocytosis are manifested.
The formation of carrier status can be facilitated by:
Congenital, genetically determined characteristics of the macroorganism;
Weakening of protective reactions due to previous and concomitant diseases;
Reduced immunogenicity of the pathogen (reduced virulence, transformation into L-forms).
The following factors are associated with the formation of carriage:
Chronic inflammatory diseases of various organs and systems;
Helminthiases;
Treatment defects;
The nature of the course of the infectious disease, etc. The duration of carriage of various pathogenic microorganisms can
vary extremely widely - from several days (transient carriage) to months and years (chronic carriage). Sometimes (for example, with typhoid fever) carriage can persist for life.
PATHOGENETIC MECHANISMS OF INTOXICATION SYNDROME FORMED UNDER THE INFLUENCE OF LIPOPOLYSACCHARIDE COMPLEX
Thanks to numerous studies by domestic and foreign scientists, the mechanisms of sequential responses that occur in the human body under the influence of bacterial endotoxins of most microorganisms have been deciphered. The combination of these reactions represents the activation or inhibition of the functional state of various organs and systems of the body, which is expressed in the development of intoxication syndrome. From a biological point of view, intoxication syndrome is a systemic response of the body to the influence of a foreign agent.
The human body’s resistance to the penetration of endotoxin into the internal environment begins with the active destruction of the pathogen with the help of cellular (macrophages, polymorphonuclear leukocytes and other phagocytes) and humoral (specific and nonspecific) factors. First of all, LPS and other pathogen-associated molecules are recognized (PAMP), carried out using TLR. Without recognition and detection, a protective response of the macroorganism is impossible. In cases where endotoxin manages to penetrate the blood, the antiendotoxin defense system is activated (Fig. 2-1). It can be presented as a combination of nonspecific and specific factors.
Rice. 2-1. Antiendotoxin defense system
Nonspecific factors of antiendotoxin protection include cellular (leukocytes, macrophages) and humoral mechanisms. The participation of humoral factors in protective reactions continues to be studied, but the fact that high-density lipoproteins primarily stand in the way of endotoxin is no longer disputed. Having the unique ability to adsorb the LPS complex, they neutralize and then remove endotoxin from the human body.
Proteins in the acute phase of inflammation have the same properties:
Albumin;
Prealbumin;
Transferrin;
Haptoglobin.
Specific factors of antiendotoxin protection include Re-AT and glycoproteins (LBPs) that bind the LPS complex to CD 14+ -cells. Re-AT
are constantly present in the blood, as they are produced in response to the effects of endotoxin coming from the intestines. Consequently, the strength of the neutralizing antitoxin effect depends on their initial concentration, as well as on the ability of their rapid synthesis in cases of excessive intake of LPS complexes.
Glycoprotein (LBP) from the group of proteins of the acute phase of inflammation is synthesized by hepatocytes. Its main function is to mediate the interaction of the LPS complex with specific receptors of myeloid cells CD 14+. The LPS complex and LBP enhance the reconciling effect of lipopolysaccharides on granulocytes, mediating the production of reactive oxygen species, TNF and other cytokines.
Only after overcoming the powerful mechanisms of anti-endotoxin defense does the LPS complex begin to exert its effect on the organs and systems of the macroorganism. At the cellular level, the main target of the LPS complex is the activation of the arachidonic cascade, which becomes the leading damaging factor in endogenous intoxication. It is known that the regulation of cell activity is realized, among other things, through the release of arachidonic acid from phospholipids of the cell membrane. Under the influence of catalysts, arachidonic acid is gradually broken down to form PG (arachidonic cascade). The latter regulate cell functions through the adenylate cyclase system. Under the influence of the LPS complex, the metabolism of arachidonic acid occurs along the lipoxygenase and cyclooxygenase pathways (Fig. 2-2).
Rice. 2-2. Education biologically active substances from arachidonic acid
The end product of the lipoxygenase pathway is leukotrienes. Leukotriene B4 enhances chemotaxis and degranulation reactions, and leukotrienes C4, D4, E4 increase vascular permeability and reduce cardiac output.
When arachidonic acid is broken down through the cyclooxygenase pathway, prostanoids (intermediate and final forms) are formed. Under the influence of the LPS complex, an excess amount of thromboxane A2 appears, causing vasoconstriction, as well as platelet aggregation throughout the vascular bed. As a result, blood clots form in small vessels and develop
microcirculatory disorders leading to disruption of tissue trophism, retention of metabolic products in them and the development of acidosis. The degree of disturbance of the acid-base state (ABC) largely determines the strength of intoxication and the severity of the disease.
The development of microcirculatory disorders due to changes in the rheological properties of blood is the morphological basis of the intoxication syndrome. In response to the increased formation of thromboxane A 2 caused by the LPS complex, the vascular network begins to secrete prostacyclin and anti-aggregation factors that restore the rheological properties of the blood.
The influence of the LPS complex on the cyclooxygenase pathway of arachidonic acid breakdown is realized through the formation of a large number of PGs (and their intermediate forms).
Their biological activity is manifested:
Vasodilation [one of the main factors reducing blood pressure(BP) and even the development of collapse];
Contraction of smooth muscles (excitation of peristaltic waves of the small and large intestines);
Increased excretion of electrolytes, and subsequently water, into the intestinal lumen.
The entry of electrolytes and fluid into the intestinal lumen, combined with increased peristalsis, is clinically manifested by the development of diarrhea, leading to dehydration.
In this case, dehydration of the body goes through several successive stages:
Decrease in the volume of circulating blood plasma (blood thickening, increase in hematocrit);
Decrease in the volume of extracellular fluid (clinically this is expressed by a decrease in skin turgor);
Development of cellular hyperhydration (acute edema and swelling of the brain).
In addition, GHGs exhibit pyrogenic properties; their excessive formation leads to an increase in body temperature.
Simultaneously and in interaction with the arachidonic cascade, the LPS complex activates myeloid cells, which leads to the formation of a wide range of endogenous mediators of lipid and protein nature (primarily cytokines), which have exceptionally high pharmacological activity.
Among cytokines, TNF occupies the leading place in the implementation of the biological effects of the LPS complex. This is one of the first cytokines whose level increases in response to exposure to the LPS complex. It promotes activation of the cytokine cascade (primarily IL-1, IL-6, etc.).
Thus, the initial damaging phase of the intoxication syndrome, formed under the influence of the LPS complex, is realized through the activation of the arachidonic and cytokine cascades, resulting in a breakdown of the control system of cellular functions. In such situations, ensuring the vital functions of the human body and maintaining its homeostasis require the inclusion of higher regulatory mechanisms. The tasks of the latter include creating conditions for removing the pathogen source of LPS complexes and restoring unbalanced functions
cellular systems. This role is performed biologically active compounds, involved in adaptation mechanisms, as well as regulating systemic reactions of the body.
For the first time, the role of glucocorticoid hormones in the development of stress syndrome as an adequate adaptive response to damage was determined by the Canadian biochemist Hans Selye. At the height of intoxication, the adrenal cortex is activated, leading to an increased release of glucocorticoids into the blood. These reactions control blood pressure under conditions of increased vascular permeability and a sharp change in the rheological properties of the blood (increased thrombus formation, microcirculation disorders and organ trophism). When the potential and reserve capabilities of the adrenal cortex are depleted, acute cardiovascular failure (collapse) develops.
The regulatory role of the renin-angiotensin-aldosterone system increases at the height of endogenous intoxication, especially against the background of dehydration (diarrhea during acute intestinal infections). Thanks to its activation, the body tries to maintain the water-electrolyte composition in liquid volumes, i.e. maintain the constancy of homeostasis.
Activation of plasma kallikreinogenesis under conditions of intoxication leads to changes in the phase structures of the systoles of the left and right ventricles of the heart.
At the height of intoxication, the exchange of serotonin and histamine increases, which is directly related to platelet aggregation in the vascular bed and the state of microcirculation.
There is an intensive study of the participation of the catecholamine system in the development of intoxication, as well as other systems involved in controlling the vital functions of the body.
Analyzing the given data on the known and studied mechanisms of development of intoxication syndrome, special attention should be paid to 2 provisions:
Sequence of activation of protection mechanisms;
Interaction of various systems for controlling the functions of organs and systems of the body.
Exactly interaction of management systems aimed at preserving and(or) restoration of homeostasis in the human body can be defined as an adaptation syndrome.
Activation of regulatory mechanisms that arise in response to the damaging effect of the LPS complex is realized through the functionality of various organs and systems. With the development of intoxication, almost all organ cellular systems are involved in the process of maintaining homeostasis of the body and removing endotoxin. In Fig. 2-3 show the systemic reactions of the body against the background of intoxication.
Based on general pathological approaches, a concept of the medical and biological significance of intoxication syndrome in the development of infectious diseases was developed. Intoxication syndrome is of unique importance for the clinic of infectious diseases, since, on the one hand, it represents a universal clinical syndrome complex, the development of which is typical for most infectious diseases, regardless of etiological factor, and on the other hand, the degree of its severity determines the severity and outcome of the disease. In general pathological terms, intoxication syndrome is clinical
Rice. 2-3. Systemic reactions of the body in response to intoxication
equivalent to urgent adaptation of the body in conditions of microbial invasion. Of exceptional importance for the clinic of infectious diseases is the establishment of the nature of the failure in the regulation of the adaptive potential of the body, which is clinically manifested by more severe forms of the disease, the development of complications and, in as a last resort, fatal.
It must be emphasized that changes in the parameters of the functional state of a single organ or a single cellular system during intoxication syndrome often do not always indicate damage to this organ or system. On the contrary, deviations of indicators of the functional state of an organ from normal may be an indicator of the need to compensate for damaged functions or their temporary replacement (for example, tachycardia due to dehydration).
Organ pathology should be discussed only if the infectious agent directly affects organ tissue (for example, with HAV)
or the reserve capacity of the organ is depleted due to its hard work. Pathological changes and reactions of organ systems (positive or negative) are presented in the “Special part” section.
Extremely unfavorable outcome of infectious diseases - development of ITSH, and in some of them (for example, in the terminal stage of cholera, salmonellosis) and hypovolemic shock(Fig. 2-4).
The clinical picture of shock is described in the relevant sections of this textbook. However, it is necessary to imagine what mechanisms underlie this condition, which represents shock from a pathophysiological point of view.
According to the authors of the textbook, shock can occur against the background of spent reserves of the body, without restoration of which conditions are created that are incompatible with life. However, this condition can be reversible if the missing reserves are replenished from the outside.
At the same time, it is known that in the body of a person who has died from shock, in some cases the vital reserves remain far from being fully used. In this situation, shock apparently occurs due to a failure of the system that controls the functions of organs and systems. At the current level of development of biology and medicine, this pathogenetic mechanism is extremely difficult to restore due to insufficient knowledge in this area and, therefore, the inability to develop a system to combat this condition. In these cases, the shock should be considered irreversible.
PATHOGENESIS OF VIRAL DISEASES
The main difference between viruses and other infectious agents is their mechanism of reproduction. Viruses are not capable of self-replication. The pathogenesis of viral infections is based on the interaction of the viral genome with the genetic apparatus of the sensitive cell. Some viruses are able to multiply in a wide variety of cells, while others multiply only in the cells of certain tissues. This is due to the fact that the number of specific receptors that ensure the interaction of the virus with cells is limited in the latter case. The entire replicative cycle of the virus is carried out using the metabolic and genetic resources of the cell. Therefore, the nature of the development of interstitial processes is determined, on the one hand, by the cytopathic effect of the virus on the cells of a given tissue and organ, and on the other hand, by the reaction of interstitial and organ systems of protection against the virus. The latter are often destructive in nature, aggravating the course of the disease.
The spread of viruses in the body can be local or systemic.
With the exception of lesions caused by viruses spreading through the nervous tissue, viral infection occurs with viremia. Viremia is characterized by the degree of viral load, which directly correlates with the degree of general toxicosis and the severity of the patient's condition.
Viremia leads to excessive secretion lymphokines by endothelial cells and damage to the walls of blood vessels with the development of hemorrhages, capillary toxicosis, tissue hemorrhagic edema of the lungs, kidneys and others parenchymal organs. A number of viruses are characterized by the induction of programmed cell death, i.e. apoptosis of infected cells.
Rice.2 -4. Scheme of development of intoxication (Malov V.A., Pak S.G., 1992)
Many viruses infect immunocompetent cells. This is more often manifested by dysfunction and a decrease in the number of T-helper cells, which leads to hyperactivation of the B-cell component of immunity, but with a decrease in the functionality of plasma cells for the synthesis of high-affinity antibodies. At the same time, there is an increase in the content and activation of T-suppressor cells, as well as B-cells.
There are latent forms of viral infections, in which viruses remain in the body for a long time without clinical manifestations, but under the influence of unfavorable factors they can be reactivated and cause an exacerbation of the disease (most herpes viruses), as well as the development of slow infections. The latter are characterized by a long incubation period (months and years), during which the pathogen multiplies, causing obvious tissue damage. The disease ends with the development of severe lesions and death of the patient (subacute sclerosing panencephalitis, HIV infection, etc.).
MAIN CLINICAL MANIFESTATIONS
INFECTIOUS DISEASES
The division of diseases into infectious and non-infectious is very arbitrary. In the vast majority of cases, the disease is the result of the interaction of an infectious agent (bacteria, viruses, etc.) and a macroorganism. However, many types inflammatory lesions lungs (pneumonia), heart (septic endocarditis), kidneys (nephritis, pyelonephritis), liver (abscesses) and other organs are not formally classified as infectious diseases.
If we base the division of these groups of diseases on the epidemiological factor, then diseases such as tetanus, brucellosis, botulism and many others classified as infectious do not pose an epidemic danger in the community. At the same time, chronic viral hepatitis, which is treated mainly by therapists, can be transmitted from person to person.
Taking into account the above circumstances, this section provides clinical description the main symptoms and syndromes that arise from the interaction of micro- and macroorganisms during the development of diseases, regardless of whether they are classified as infectious or non-infectious.
The vast majority of infectious diseases are characterized by general toxic syndrome. Clinically, it is a frequent combination of fever with numerous other manifestations of intoxication.
Fever- any increase in body temperature over 37 °C. Its character (temperature curve) is very typical for many infectious diseases, which serves as an important diagnostic sign. It is not typical for only a few manifest forms of infectious diseases (for example, cholera and botulism). Fever may also be absent in cases of mild, erased or abortive disease.
Main criteria for fever:
Duration;
Height of body temperature;
The nature of the temperature curve.
Most often, acute fever lasting no more than 15 days is observed. Fever lasting from 15 days to 6 weeks is called subacute, more than 6 weeks - subchronic and chronic. Based on height, body temperature is divided into subfebrile (37-38 °C), moderate (up to 39 °C), high (up to 40 °C) and hyperpyretic (over 41 °C).
Based on the nature of the temperature curve, taking into account the difference between the highest and lowest temperatures of the day, the following main types of fever are distinguished.
. Constant fever (febris continua). Characteristic fluctuations between morning and evening temperatures do not exceed 1 °C. It is observed in typhoid and typhus, yersiniosis, and lobar pneumonia.
. Remitting or remitting fever (febris remittens). Typical daily temperature fluctuations (not decreasing to normal) range from 1-1.5 °C. Observed in some rickettsioses, tuberculosis, purulent diseases, etc.
. Intermittent or intermittent fever (febris intermittens). Characterized by regular alternations of periods of increased body temperature, usually rapid and short-term (paroxysms of fever), with fever-free periods (apyrexia). At the same time, its minimum indicators for 1 day are within the normal range. This type of fever is observed in malaria, some septic conditions, and visceral leishmaniasis.
. Relapsing fever (febris reccurens). It is represented by alternating attacks of high body temperature with its rapid rise, critical fall and periods of apyrexia. The febrile attack and apyrexia last for several days. This type of fever is characteristic of relapsing fever.
. Hectic or wasting fever (febris hectica). Characterized by sharp increases in body temperature by 2-4 °C and rapid drops to normal levels and below, which are repeated 2-3 times during the day and are accompanied by profuse sweating. Occurs in sepsis.
. Undulating or undulating fever (febris undulans). The temperature curve is characterized by alternating periods of a gradual increase in temperature to high levels and a gradual decrease to subfebrile or normal levels. These periods last several days (brucellosis, some forms of yersiniosis, recurrent typhoid fever).
. Irregular, or atypical, fever (febris irregularis, sine atypica). Various and irregular daily fluctuations of indefinite duration are characteristic. Observed in many infectious diseases (influenza, diphtheria, tetanus, meningitis, anthrax, etc.).
. Reverse fever. Sometimes found in brucellosis and septic conditions. At the same time, morning body temperature indicators exceed evening ones.
There are three periods during fever:
Build-up;
Stabilization;
Decrease in body temperature.
Identification of these periods with their clinical assessment is important for diagnosing an infectious disease and for determining a set of measures for medical care of the patient.
With the acute onset of the disease (influenza, typhus, meningococcal meningitis, erysipelas, leptospirosis, etc.), the increase in body temperature to high numbers occurs quickly, within 1 day or even several hours. The gradual onset of the disease is accompanied by an increase in fever over several days, as happens, for example, in cases of the classic course of typhoid fever. The fever ends either very quickly, after a few hours (critical decrease in temperature), or slowly, gradually, over several days (lytic decrease).
In some cases, with a severe course of the infectious disease, hypothermia is noted - not an increase, but a drop in body temperature below the normal level. The combination of hypothermia with increasing symptoms of intoxication and hemodynamic disorders is extremely unfavorable and indicates the development of ITS.
Fever in infectious diseases is usually accompanied by other manifestations of intoxication associated with damage to various organs and systems. With the development of toxinemia, first of all, signs of damage to the central nervous system are observed (headache, weakness, malaise, sleep disturbance), or more pronounced signs toxic encephalopathy (excitement or apathy, emotional lability, anxiety, disturbances of consciousness of varying degrees, up to deep coma).
Intoxication also leads to disorders of cardiovascular activity:
Bradycardia or tachycardia;
Deafness of heart sounds;
Decrease or increase in blood pressure.
Changes in the color of the skin and mucous membranes (icterus, cyanosis, pallor or hyperemia), dry mucous membranes and thirst, a decrease in the amount of urine excreted (oliguria, anuria) and many other clinical symptoms occur.
Important diagnostic signs revealed during examination of an infectious patient are: changes in the skin and mucous membranes- their color, elasticity and humidity, various rashes on them. Pale skin may indicate spasm of blood vessels or blood deposition in the abdominal cavity (for example, with ITS). The appearance of cyanosis is associated with severe metabolic disorders and tissue hypoxia (with meningococcemia, severe salmonellosis, sepsis, etc.).
Some infectious diseases (influenza, typhus, pseudotuberculosis) are characterized by hyperemia of the skin, mainly of the face and upper half of the body. Due to liver damage or hemolysis of red blood cells, icteric discoloration of the skin, sclera and mucous membranes can be observed (viral hepatitis, leptospirosis).
Dry skin and decreased elasticity (turgor) indicate significant dehydration. Severe sweating is observed in malaria, brucellosis, sepsis, and pneumonia. Usually it accompanies the stages of a critical decrease in body temperature.
Many infectious diseases are characterized by skin rashes (exanthema).
The elements of the rash are quite varied:
Roseola;
spots;
Erythema;
Hemorrhages;
Papules;
Vesicles;
Pustules;
Blisters.
Later, the primary elements of the rash may be replaced by the formation of scales, age spots, ulcers and scars. The nature of the exanthema, the timing of its appearance (day of illness), the sequence (stages) of the rash, the preferential localization, the number of elements of the rash and the subsequent dynamics of their development are of great diagnostic importance.
With some vector-borne infections (tularemia, borreliosis, etc.), a primary affect- an area of inflammation of the skin that precedes other clinical manifestations of the disease.
When examining the mucous membranes you can find enanthema with the formation of vesicles, erosions and ulcers, small hemorrhages (Chiari-Avtsyn spots on the transitional fold of the conjunctiva in patients with typhus), foci of epithelial necrosis (Belsky-Filatov-Koplik spots on the mucous membrane of the cheeks in measles).
Great diagnostic importance is attached to the identified changes in the mucous membranes of the eyes:
Conjunctival hyperemia;
Scleral vascular injections (flu, measles, leptospirosis);
Formation of fibrinous films on the conjunctiva with severe swelling of the eyelids (diphtheria of the eye, membranous adenoviral conjunctivitis).
You can observe changes in the color of the mucous membranes - icterus of the sclera, soft palate, frenulum of the tongue in case of liver damage, cyanotic tint of the mucous membranes of the oropharynx in diphtheria.
Many infectious diseases are accompanied by lymphadenopathy- increase lymph nodes. During examination and palpation, their size, consistency, pain, mobility, and their adhesion to the surrounding tissue and skin (periadenitis) are assessed. In unclear diagnostic cases, puncture and biopsy of lymph nodes are performed. Specific changes in isolated groups of lymph nodes, the so-called regional lymphadenitis, are observed in plague, tularemia, felinosis (disease cat scratches), diphtheria, various types of tonsillitis. Such changes are called regional because they develop near the entrance gate of infection and represent the place of primary localization and accumulation of the pathogen. When 2-3 groups of lymph nodes or more are involved in the process, they speak of generalized lymphadenopathy. It is characteristic of HIV infection, brucellosis, infectious mononucleosis, chlamydia, etc.
Some infections are characterized by joint damage in the form of mono-, poly- and periarthritis (brucellosis, yersiniosis, meningococcal infection, borreliosis).
Catarrhal-respiratory syndrome clearly expressed in ARVI and manifests itself:
Runny nose;
Cough;
Sneezing;
Pain and soreness in the throat and nasopharynx.
When examining patients, hyperemia is revealed, in some cases swelling of the mucous membranes of the upper parts of the respiratory tract, plaques of various types (loose follicular or lacunar in sore throats of coccal etiology, fibrinous localized or widespread in diphtheria, etc.). Bronchitis, bronchiolitis and pneumonia often develop; the latter in some infectious diseases are of a specific nature (Q fever, legionellosis, mycoplasmosis, ornithosis).
Changes in the cardiovascular system are characteristic of many infectious diseases and are often associated with the development of intoxication. However, with some infections, changes in the heart and blood vessels are specific manifestations of the disease (diphtheria, hemorrhagic fevers, typhus, meningococcal infection).
The most typical clinical picture of acute intestinal infections is diarrhea. It is usually combined with a variety of dyspeptic disorders, which vary significantly with different intestinal infections - abdominal pain, nausea and vomiting, appetite disturbances, as well as fever and other symptoms of general intoxication (shigellosis, salmonellosis, escherichiosis, yersiniosis, viral enteritis and etc.). Since the nature of the stool is associated with the development of pathological processes in different parts of the gastrointestinal tract, examination plays an important role in making the diagnosis of intestinal infections. When the small intestine is affected, enteritic stool is observed - frequent and abundant, liquid, watery, with particles of undigested food, foamy, foul-smelling, greenish or light yellow in color. In a pathological process in the colon, colitis is observed - mushy or semi-liquid consistency, brown in color, frequent, the volume of feces tends to decrease with each subsequent bowel movement. Pathological impurities in the form of mucus or blood may be detected in the stool. In severe colitis, stool is scanty and consists only of mucus, streaks or droplets of blood, sometimes admixtures of pus (rectal spit). At the same time, one can observe false urges and painful contractions of the colon - tenesmus.
Typhoid-paratyphoid diseases can complicate the development of heavy intestinal bleeding. In this case, the stool takes on a tarry appearance. (melena).
At the same time, it should be taken into account that the nature of the stool (primarily its color) may be associated with the food products consumed by the patient (beets, blueberries, etc.).
One of the important manifestations of many infectious diseases accompanied by the circulation of the pathogen in the blood is hepatolienal syndrome. It is expressed in a combined enlargement of the liver and spleen, which is explained by active reactions of reticulohistiocytic tissue in these organs.
Hepatolienal syndrome is formed with viral hepatitis, brucellosis, leptospirosis, malaria, typhus, typhoid-paratyphoid and others
infectious diseases occurring in a generalized form. Using percussion and palpation, the size of the liver and spleen, their consistency, sensitivity or soreness of the organs are assessed.
Meningeal syndrome develops with meningitis of various etiologies. It is usually combined with general toxic manifestations and changes in the cerebrospinal fluid. The ability to identify its signs is extremely important for the early diagnosis of diseases and the timely start of full treatment, on which the fate of the patient often depends. Meningeal syndrome includes cerebral and meningeal symptoms.
General cerebral symptoms are an increasingly intense headache of a diffuse, bursting nature, sudden vomiting without previous nausea and, as a rule, not bringing relief to the patient, as well as disturbances of consciousness of varying degrees, up to deep coma.
Shell symptoms - auditory, visual and tactile hyperesthesia, pain when pressing on eyeballs with closed eyelids, at the exit points of the branches trigeminal nerve and occipital nerves, with percussion of the skull.
Along with general cerebral and meningeal symptoms, meningeal symptoms occur in the form of stiffness of the neck muscles, Kernig’s, Brudzinsky’s symptoms, etc.
Rigidity of the neck muscles is detected when trying to passively bend the head of a patient lying on his back to his chest.
Kernig's symptom is expressed in the impossibility of full passive extension at the knee of the patient's leg, which is previously bent at a right angle at the hip joint (checked on both sides).
The upper Brudzinski sign is determined in a patient lying on his back, simultaneously with an attempt to identify stiff neck muscles: in this case, one or both legs of the patient spontaneously bend at the knees and hip joints. The same spontaneous flexion of the patient’s legs in a supine position can occur when pressing on the symphysis pubis or when checking Kernig’s sign (middle and lower Brudzinski’s symptoms, respectively).
Along with the above main meningeal symptoms, many others may be present (Guillain, Gordon, hanging symptom, or Lessage, etc.).
Children in the first year of life are characterized by bulging and tension of the large fontanel. At an older age, a symptom of sitting up (tripod) appears: when trying to sit up in bed, the child moves his arms back and leans them on the bed, supporting the torso in an upright position.
The severity of individual symptoms and meningeal syndrome as a whole may vary, but in all cases a lumbar puncture and examination of the cerebrospinal fluid (CSF) are indicated.
If there are no changes in the cerebrospinal fluid in a patient with positive meningeal symptoms, they speak of meningism. The condition can develop in infectious diseases accompanied by severe general toxic reactions, for example with the flu.
Along with the listed main syndromes, in some infectious diseases, specific lesions of individual organs are identified:
Kidney - for hemorrhagic fever with renal syndrome (HFRS) and leptospirosis;
Genital organs - with brucellosis, mumps and etc.
BASIC METHODS FOR DIAGNOSIS OF INFECTIOUS DISEASES
Diagnosis of infectious diseases is based on the integrated use of clinical, laboratory and instrumental examination methods.
Clinical diagnosis
Clinical methods include:
Identification of patient complaints;
Anamnestic information (medical history, epidemiological history, basic information from the life history);
Clinical examination of the patient.
History of infectious disease are found out by actively questioning the patient: detailed identification of his complaints at the time of examination by a doctor, the time and nature of the onset of the disease (acute or gradual), a detailed and consistent description of the occurrence of individual symptoms and their development in the dynamics of the disease. In this case, one cannot limit oneself to the patient’s story (if his condition allows); the anamnestic data is clarified in as much detail as possible. This allows the clinician to form a preliminary impression of the likely clinical diagnosis. The old rule of clinicians is: “History is half the diagnosis.”
When collecting anamnestic information from infectious patients, special attention must be paid to the data epidemiological history. In this case, the doctor aims to obtain information about the place, circumstances and conditions under which the infection could occur, as well as about the possible ways and means of transmitting the infectious agent to a given patient. They find out the patient’s contacts and frequency of communication with other sick people or animals, his stay in places where infection could occur (in endemic or epizootic foci). Pay attention to the possibility of insect and animal bites, any damage to the skin (injuries, wounds), therapeutic parenteral interventions.
When finding out life history pay attention to the living conditions, nutrition, work and rest of the patient. Information about previous diseases, including infectious ones, and the treatment carried out for this is extremely important. It is necessary to find out whether the patient has received preventive vaccinations (which and when), whether there is a history of indications for the administration of serums, immunoglobulins, blood products and blood substitutes, as well as possible reactions to them.
Clinical examination The patient is examined in a certain order in accordance with the medical history chart. Consistent and detailed examination allows us to identify symptoms and syndromes characteristic of an infectious disease (see section “Main clinical manifestations of infectious diseases”).
First of all, assess the general condition of the patient:
Preservation of consciousness or the degree of its impairment;
Excitement or lethargy;
Mental disorders;
Adequacy of behavior.
In accordance with the established procedure, the examination is carried out:
Skin and mucous membranes;
Peripheral lymph nodes;
The condition of the musculoskeletal system, respiratory, cardiovascular systems, gastrointestinal tract, urinary organs, genital organs, and nervous system is assessed.
Based on the information obtained by the doctor when identifying anamnestic information and data from the clinical examination of the patient, a preliminary diagnosis is formulated.
In accordance with the diagnosis (with an assessment of the form and severity of the disease, the period of illness, complications and concomitant diseases), the doctor determines:
Place of hospitalization of the patient in an infectious diseases hospital, department (resuscitation room if necessary), ward or isolated box;
Develops a plan for laboratory and instrumental examinations, consultations with specialists;
Draws up a treatment plan for the patient (regimen, diet, medication).
All this data is entered into the medical history.
Laboratory and instrumental diagnostics
Laboratory and instrumental diagnostic methods are divided into general (for example, general blood and urine tests, chest x-ray) and specific (special), used to confirm the suspected diagnosis of an infectious disease and assess the severity of the disease. Data from specific studies are also necessary to monitor recovery and determine the timing and conditions for the patient’s discharge.
Depending on the nosological form of the disease, its nature and period, the following may be subject to specific research:
Blood;
Feces;
Urine;
Sputum;
Cerebrospinal fluid;
Duodenal contents;
Washings from mucous membranes;
Organ punctures and biopsies;
Discharge from ulcers;
Sectional material. Laboratory research methods
Bacteriological studies provide for sowing nutrient media various material taken from the patient (blood, urine, cerebrospinal fluid, feces, etc.), isolating a pure culture of the pathogen, as well as determining its properties, in particular its type and sensitivity to antibiotics. During outbreaks of intestinal infections, food remains that may be associated with infection of those who consumed them are subjected to bacteriological examination. Bacteriological research takes at least several days.
Virological studies involve the isolation and identification of viruses. They use tissue cultures, chicken embryos, and laboratory animals. Quite often, such studies are carried out in secure laboratories.
Immunological methods based on the detection of pathogen Ags or antibodies to them.
The pathogen's antigens are detected in feces, blood serum, cerebrospinal fluid, saliva and other biological material obtained from the patient. For this use:
Coagglutination reactions (CAR);
Latex agglutination reactions (RLA);
RNGA;
ELISA, etc.
Reactions are based on the use of special diagnostic drugs (diagnosticums), which are a carrier (lyophilized staphylococcus, latex particles, red blood cells) with a highly active serum fixed on it against a particular pathogen Ag. The reactions are highly specific and can be used as rapid diagnostic methods in the early stages of the disease.
AT in whole blood serum or its fractions containing immunoglobulins of various classes can be detected using many specific laboratory methods.
The most popular of them:
RA - for brucellosis, yersiniosis, tularemia, some rickettsioses and other infections;
RNGA - for many intestinal infections;
RTGA - for various viral infections.
For rickettsioses and some viral diseases, the complement fixation reaction (FRT), radioimmunoassay (RIA) and ELISA are of great diagnostic importance. Research is carried out with known Ags. Determining whether antibodies belong to different classes of immunoglobulins helps to clarify the phase of the infectious process, distinguish a primary infectious disease from a recurrent one (for example, typhus from Brill-Zinsser disease), and differentiate an infectious disease from post-vaccination reactions.
However, AT detection methods also have significant drawbacks. Usually, positive results reactions can be obtained no earlier than the 2nd week of the disease, when serum antibody titers begin to exceed the minimum diagnostic level. Weak or delayed formation of antibodies is observed in individuals with reduced activity of the immune system, as well as in many infectious diseases, the causative agents of which exhibit high immunosuppressive activity (yersiniosis, abdominal
typhus, etc.). The diagnostic value of reactions increases when examining paired sera taken at intervals of 7-10 days. In these cases, the dynamics of the increase in AT titers is monitored, which is most important for viral infections, when only an increase in titers in the 2nd portion of serum by 4 times or more has diagnostic significance.
IN last years In healthcare practice, other immunological methods are widely used - determination of markers of viral hepatitis (Ag viruses and antibodies to them), determination of immunoglobulins of different classes, quantitative content of T-lymphocytes, immunoblotting, etc.
Currently, polymerase chain reaction (PCR) is of great importance for the diagnosis of infectious diseases, which detects the minimum amount of nucleic acids of almost any pathogenic pathogen in various biological fluids and cellular elements of the macroorganism.
Skin allergy tests used for allergological diagnosis of brucellosis, tularemia, anthrax, toxoplasmosis, ornithosis and other infectious diseases. To do this, 0.1 ml of a specific allergen (protein extract of the pathogen culture) is injected intradermally or applied to scarified skin. The test is considered positive if hyperemia, swelling and infiltration appear at the site of allergen injection after 24-48 hours, the severity of which is used to judge the intensity of the reaction.
Biochemical research methods occupy a significant place in the practice of an infectious disease doctor. They are especially popular for infectious diseases accompanied by damage to the liver, kidneys, cardiovascular, endocrine systems, etc.
Instrumental research methods
For the differential diagnosis of certain intestinal infections and to establish the nature and depth of damage to the mucous membrane of the rectum and sigmoid colon, sigmoidoscopy has long been practiced. The method allows you to examine the condition of the mucous membrane of the large intestine along, but not further than 30 cm from the anus. Recently, sigmoidoscopy is inferior in diagnostic value to fibrocolonoscopy and x-ray examination(irrigoscopy), revealing pathological changes at the level of deeper parts of the intestine.
In case of echinococcosis and alveococcosis, the localization and intensity of lesions can be identified using a liver scan. When identifying focal lesions of visceral organs, the most popular methods are ultrasound examination (ultrasound). They are invaluable in the differential diagnosis of diseases accompanied by jaundice (viral hepatitis, neoplasms of the liver and its gate area, stones in the bile ducts and gallbladder and etc.). Laparoscopy and liver puncture biopsy are also used for this purpose.
In the diagnosis of infectious diseases, X-ray examination methods (especially examination of the lungs during ARVI), electrocardiography (ECG) and computed tomography (CT) are also used.
The presented research methods are most often used in infectious diseases practice, however, for the diagnosis of infectious diseases and especially differential diagnosis, it is necessary to use any other methods used by clinicians.
GENERAL PRINCIPLES OF TREATING INFECTIOUS PATIENTS
Advances in the field of early diagnosis and treatment of infectious diseases, great achievements in epidemiology and improvement of social and living conditions of people now make it possible to observe and treat patients with certain infectious diseases who were previously subject to hospitalization on an outpatient basis (in the clinic and at home). These diseases include PTI, shigellosis, HAV and a number of others. Of course, it is desirable (with the consent of the patients) for their hospitalization with the listed diseases according to clinical indications - in cases of severe and protracted course, complications, severe concomitant diseases.
However, the general principles of treatment of infectious patients in outpatient and inpatient settings remain the same.
Infectious patients regime
The treatment regimen for infectious patients is determined by the attending physician in accordance with the following conditions: the severity of the disease, the timing of the infectious process, the severity of the pathology of certain organs and systems, as well as the possibility of developing complications. The regimen prescribed to the patient is noted in the medical history.
Regime I - strictly bed rest. The patient is forbidden to sit down, much less stand up; caring for him, feeding and all medical manipulations are carried out with the patient in bed. For some infectious diseases (typhoid and typhus, etc.), strict bed rest is prescribed for a long time. It is necessary to explain to the patient the reasons for the prescription. bed rest, the possible consequences of its violation and strictly monitor its compliance.
Mode II - semi-bed (ward). It is possible for the patient to independently visit the toilet, treatment room, and eat in the ward, but it is recommended to spend most of the time in bed.
Mode III - general. Prescribed when the patient is in good health and in satisfactory condition, if the risk of developing complications and consequences of the disease is completely excluded. The patient is allowed to serve himself independently and visit the dining room.
The infectious diseases department regime also applies to medical staff, who should try to eliminate as much as possible the factors that disturb the patient’s peace:
Unrestrained and harsh tone when communicating with him;
Loud conversations in wards and corridors.
It is especially strictly necessary to maintain silence at night. The severity of the patient's condition should not be discussed in his presence, even if the patient is unconscious.
Caring for infectious patients
Qualified care for infectious patients contributes to their recovery, prevention of complications, and helps prevent infection of others.
It is very important to maintain an even, calm tone when communicating with patients. It should be remembered that the patient’s irritability and rudeness can be caused not only by a low level of culture and moral principles, but also by a peculiar reaction to the environment, shifts in the psycho-emotional state caused by a long and severe infectious disease. At the same time, the necessary measures should be persistently carried out and the patient should be forced to comply with the regime of the infectious diseases department. This requires a medical worker to know the basic principles of medical ethics and deontology, including the features of subordination, professional behavior, appearance, and the ability to apply them in everyday activities.
In the infectious diseases department, it is necessary to systematically carry out wet cleaning of premises using disinfectants, ventilation of rooms. Particular attention is paid to the cleanliness of the patient’s body and bed. Patients are washed in a bath or shower at least once a week. If this is contraindicated, wipe the patient's skin daily with a towel moistened with warm water. Seriously ill patients are treated with oral and nasal cavity treatment, prevention of bedsores and congestive pneumonia, and physiological functions are monitored.
Nutrition of the sick
Nutrition of patients is carried out taking into account the specifics of the development of the infectious disease. Nutrition should be sufficiently high in calories and meet all the body's needs for food, liquid, vitamins and salts. Infectious patients and those recovering are fed at least 4 times a day (breakfast, lunch, afternoon snack and dinner) at strictly defined times. Seriously ill patients are given food in small portions 6-8 times a day.
Dietary food is prescribed by the attending physician, and the patient’s diet is monitored by a nurse. Products brought by visitors are checked in their presence and returned immediately if they do not comply with the prescribed diet. It is necessary to systematically monitor the storage conditions of food brought to the patient in bedside tables and specially designated refrigerators.
In general, the nutrition of infectious patients is carried out using certain types of diets that correspond to the identified pathology.
The following types of diets are most often used in infectious diseases hospitals.
Diet No. 2 is prescribed for acute intestinal infections during the period of convalescence for a long period. It provides mechanical and thermal sparing of the gastrointestinal tract. The table is mixed, all dishes are prepared pureed and chopped. Exclude beans, beans, green peas.
Diet No. 4 is recommended for diarrhea accompanied by significant irritation of the gastrointestinal mucosa (dysentery, salmonellosis, some forms of escherichiosis, etc.). Allowed are meat broths, slimy soups, boiled meat in the form of cutlets and meatballs, boiled fish, pureed cereals, jelly, jellies, fruit juices enriched with vitamins. Avoid foods that cause fermentation processes and increased intestinal motility: cabbage, beets, pickles and smoked meats, spices, milk, natural coffee.
A slightly modified diet No. 4 (in infectious diseases hospitals it is sometimes referred to as diet No. 4abt) prescribed for typhoid fever and paratyphoid fever during the entire febrile period and 10-12 days of apyrexia. The diet provides maximum mechanical and chemical sparing of the intestines, reducing peristalsis and fermentation processes. Allowed are low-fat beef or chicken broths, slimy cereal soups, pureed porridge with water, meat in the form of meatballs, soufflés or steamed cutlets, boiled fish, soft-boiled eggs, white bread crackers. From the 10-12th day of apyrexia, the diet is supplemented with the inclusion of white semi-stale bread (up to 150-200 g/day). Food should be enriched with vitamins. They recommend jelly, berry and fruit juices, pureed apples. Amount of liquid - 1.5-2 l/day (tea, cranberry juice, rosehip decoction). Limit fats, carbohydrates, coarse fiber.
Diet No. 5a is indicated in the acute stage of viral hepatitis and during exacerbation of chronic hepatitis. To minimize the load on the liver, limit animal fats and extractive substances, and exclude fried foods. Dishes are prepared mainly pureed. Day-old bread, vegetable and cereal soups are allowed. pasta on vegetable or non-concentrated meat and fish broths, milk and fruit soups; boiled lean meat, fish and poultry; pureed porridge (especially buckwheat) with water or with the addition of milk; eggs, milk, butter and vegetable oil (as additives to dishes); fresh fermented milk products and cottage cheese (soufflé); fruits, berries, jam, honey, jelly, jellies, compotes, weak tea. Exclude snacks, mushrooms, spinach, sorrel, turnips, radishes, lemon, spices, cocoa, chocolate.
Diet No. 5 is prescribed during the recovery period for acute viral hepatitis or during remission for chronic hepatitis. In addition to the products of diet No. 5a, soaked herring, non-acidic sauerkraut, vegetables and herbs are allowed, raw or in the form of salads, vinaigrettes; milk, cheese, omelettes. The food is not chopped.
Diet No. 15 (common table) is prescribed in the absence of indications for special diet. A physiologically complete diet with a high content of vitamins.
When patients are unconscious or have paralysis of the swallowing muscles (for example, botulism, diphtheria), feeding is carried out through a nasal tube inserted by a doctor. Use 100-200 ml of warmed nutritional mixture from milk, kefir, broths, eggs, fruit juices, butter etc. Liquids and medications are also administered through the tube.
The calories needed by a seriously ill patient are partially compensated by parenteral nutrition, in which the following is administered intravenously:
Hydrolysates;
Amino acids;
Salts;
Vitamins;
5% glucose solution ♠ ;
Special nutritional mixtures.
In febrile conditions and dehydration, infectious patients often need drinking plenty of fluids(up to 2-3 l/day). Recommend mineral water, tea with lemon, fruit drinks (cranberry, blackcurrant, etc.), a variety of fruit and berry juices. For dehydration and demineralization, oral and intravenous administration of polyionic crystalloid isotonic solutions is prescribed.
Drug treatment
Complex drug treatment of infectious patients involves taking into account the etiology and pathogenesis of the disease, a thorough analysis of the individual condition of the patient, his age and immunological characteristics, the period and severity of the infectious disease, complications and concomitant diseases.
One of the most important areas of complex treatment of infectious patients is etiotropic treatment, those. impact on the pathogen. During this procedure, antibiotics and chemotherapy are used.
When choosing a drug, it is important to use certain rules.
The pathogen must be sensitive to the agent used.
The concentration of the chemotherapy drug (antibiotic) at the site of infection must be sufficient to suppress the vital activity of the pathogen (bactericidal or bacteriostatic effect).
The drug should be administered in such a way and at such an interval that the required concentration is maintained at the site of infection.
The negative effect of the drug on the macroorganism should be less than its healing effect.
The drug should be administered for as long as required to completely suppress the vital activity of the pathogen.
It is impossible to reduce the dose of the administered drug during treatment, despite the apparent achievement of a therapeutic effect.
The basic principles of etiotropic treatment are reduced to the isolation and identification of the causative agent of an infectious disease, the study of its sensitivity to drugs, the selection of an active and least toxic etiotropic drug (or several drugs in combination treatment), the determination of its optimal doses, method and duration of use, taking into account possible side effects . Since the timeliness of treatment is extremely important, it is often started immediately after taking material for microbiological testing, even before the pathogen is isolated. At the same time, it is advisable to avoid prescribing multiple medications and medical procedures; their volume should be limited to the minimum necessary in each specific case.
Antibiotics are widely used in infectious diseases practice. Penicillin groups (salts of gasylpenicillin, phenoximethylpenicillin, bicillin ♠, ampicillin, semi -synthetic penicillin - oxacillin, ampicillin, carbenicillin, etc.) have a bactericidal effect in relation to maccock infections, pneumonia, faces), as well as pathogens) , leptospirosis, Siberian ulcers, listeriosis. Penicillins resistant to acids and the action of β-lactamases (cloxacillin Ψ, dicloxacillin Ψ, flucloxacillin Ψ) are used for
oral administration. Cephalosporins of the I-IV generations are distinguished by a pronounced bactericidal effect against gram-positive (staphylococci and pneumococci), as well as most gram-negative bacteria. The drugs are low-toxic, but at the same time they can sometimes cause undesirable manifestations in the form of allergic and dyspeptic reactions, hemorrhagic syndrome, phlebitis (with parenteral administration). Carbapenems (imipenem, meropenem), which are classified as reserve antibiotics, have the widest spectrum of antimicrobial action. Tetracycline, chloramphenicol ♠, rifampicin are used in the treatment of yersiniosis, rickettsiosis (typhoid fever, Brill-Zinsser disease, Q fever, etc.), borreliosis, typhoid fever and paratyphoid fever, brucellosis, legionellosis, as well as chlamydia and mycoplasmosis. When pathogens are resistant to penicillin, chloramphenicol ♠ and tetracyclines, aminoglycosides are used different generations- streptomycin, neomycin, kanamycin, monomycin ♠ (I generation), gentamicin, tobramycin, sizomycin (II generation), netilmicin, amikacin (III generation), etc., however, their spectrum of action does not cover the anaerobic flora, and the toxicity is much higher, in Therefore, it is currently prohibited to prescribe first generation drugs orally. Aminoglycosides are active against gram-negative flora, staphylococci, Pseudomonas aeruginosa (drugs of II-III generations). For coccal infections, as well as whooping cough, diphtheria and campylobacteriosis, macrolides (erythromycin, oleandomycin, etc.) are prescribed. One of the best semisynthetic macrolides in terms of its pharmacological properties is azithromycin. In cases of fungal diseases, antifungal antibiotics are active - nystatin, mycoseptin ♠, etc.
The number of new antibiotics is constantly growing. To replace many drugs natural origin semi-synthetic antibiotics of the 3rd and 4th generations are coming, which have numerous advantages. However, it should be remembered that the widespread and unjustified use of antibiotics and long courses of antibiotic therapy can cause undesirable consequences: the development of sensitization with allergic reactions, dysbiosis (dysbacteriosis), decreased activity of the immune system, increased resistance of pathogenic strains of microorganisms, and many others.
A relatively new group of drugs for the etiotropic treatment of infectious diseases is fluoroquinolones. They are increasingly used in cases severe forms intestinal bacterial infections (typhoid fever, yersiniosis), mycoplasmosis and chlamydia.
When carrying out etiotropic treatment, other antimicrobial agents are also prescribed, to a lesser extent than antibiotics that cause the development of resistance of microorganisms. In the treatment of pneumonia, sore throats and some other infectious diseases, sulfonamide drugs, especially long-acting ones, can be used. Their use in combination with antibiotics often produces a synergistic therapeutic effect. However, the use of sulfonamides can cause adverse reactions: sensitization of the body, inhibition of hematopoiesis, suppression normal microflora, formation of stones in the urinary organs, irritating effect on mucous membranes.
Nitrofuran derivatives (furazolidone, furadonin ♠, furagin ♠, etc.) are effective in the treatment of many bacterial and protozoal diseases, including
including those caused by antibiotic-resistant flora. They have found application in the treatment of giardiasis, trichomoniasis, and amoebiasis.
Antiviral drugs are increasingly being introduced into the practice of treating infectious diseases. They are used in etiotropic therapy and prevention of influenza (amantadine, rimantadine ♠), herpes infection (acyclovir, etc.), viral hepatitis (ribavirin), HIV infection (azidothymidine Ψ). However, the clinical effectiveness of these drugs in many cases remains insufficiently high.
At chronic course Disease, patient adherence to treatment, that is, strict adherence to regular medication intake, carried out in some cases for life (for example, with HIV infection), is of particular importance. HIV-infected individuals who regularly use antiretroviral therapy remain healthy and able to work for many years.
Drugs are also used in the treatment of infectious diseases specific immunotherapy - immune sera (see Appendices, Table 3), immunoglobulins and γ-globulins, plasma of immunized donors. Immune sera are divided into antitoxic and antimicrobial. Antitoxic sera are represented by antidiphtheria, antitetanus, antibotulinum and antigangrenosis sera of various types. They contain specific antitoxic antibodies; they are used to neutralize pathogen toxins freely circulating in the blood in the corresponding diseases. The clinical effect of the use of antitoxic serums is most pronounced in the early stages of the disease, since serums are not able to neutralize toxins already bound by cells and tissues. Antimicrobial serums contain antibodies to pathogenic pathogens; they are rarely used in infectious practice (anti-anthrax globulin).
In the treatment of many infectious diseases (influenza, measles, leptospirosis, herpes infection, anthrax, etc.), immunoglobulins with a high concentration of AT, as well as plasma from immunized donors (antistaphylococcal, antipseudomonas, etc.), have been used.
Currently, killed vaccines are used increasingly limited due to the possibility of developing adverse reactions to the ballast substances they contain, autoimmune reactions, immunosuppressive effect, increased frequency of disease relapses.
The use of specific immunotherapy drugs requires medical supervision and strict adherence to the rules set out in the instructions for their use, since in some cases it can lead to the development of complications:
Anaphylactic shock;
Serum sickness;
Double anaphylactic reaction.
Anaphylactic shock - an immediate allergic reaction that occurs in persons with hypersensitivity. Its main pathogenetic mechanisms include the formation of immune complexes that fixate on cellular structures with their subsequent damage and the release of biologically active substances. The latter, acting on the smooth muscles of blood vessels and bronchi, lead to the development of vascular paralysis with increased permeability of the vascular walls and spasm of the smooth muscles of the organs. At the same time, circulating blood volume and cardiac output decrease. Severe complications develop in the form of acute vascular insufficiency, disseminated intravascular coagulation syndrome (DIC), cerebral and pulmonary edema, laryngeal edema with asphyxia, acute renal failure and (or) acute adrenal insufficiency.
Anaphylactic shock occurs suddenly, immediately after parenteral administration of the drug, and is characterized by a rapid, often lightning-fast course.
Clinical signs anaphylactic shock:
General anxiety of the patient;
Feeling of fear;
Headache;
Dizziness;
Feeling hot;
Hyperemia;
Puffiness of the face;
Nausea and vomiting;
General weakness.
There is a feeling of pressure in the chest, pain in the heart. Shortness of breath progresses rapidly, breathing is noisy, wheezing, with difficulty in inhaling and exhaling. There may be attacks of suffocation with coughing. Quincke's edema and urticaria are sometimes observed. At the same time, the skin becomes pale, sweating increases, blood pressure drops, tachycardia increases, and consciousness is impaired. With more gradual development state of shock Patients note itching, numbness of the lips, tongue, and face.
Emergency care for anaphylactic shock is provided on site.
It includes the following steps.
Immediately stop administering the drug that caused the anaphylactic reaction.
Apply a tourniquet above the injection site.
Inject the injection site with diluted adrenaline ♠ (1 ml of 0.1% adrenaline ♠ diluted in 5-10 ml of isotonic sodium chloride solution).
Apply ice to the puncture site.
Place the patient in a horizontal position with slightly raised legs and head turned to one side.
Place a heating pad on your feet.
Apply a tonometer cuff, record the time, measure and record blood pressure, pulse, and respiration.
Inject intravenously 0.5-1 ml of 0.1% solution of adrenaline ♠ in 10-20 ml of isotonic sodium chloride solution and 60 mg of prednisolone. Repeat
administration of adrenaline ♠ intravenously every 10-20 minutes until the patient comes out of shock or, if there is no effect, conduct an intravenous drip infusion (1-2 ml of a 0.1% solution of adrenaline ♠ in 250 ml of isotonic glucose solution ♠).
For bronchospasm and pulmonary edema, inject subcutaneously 0.5 ml of a 0.1% solution of atropine sulfate ♠, intramuscularly - 1 ml of a 2.5% solution of diprazine ♠, intravenously - 20 ml of a 40% glucose solution ♠ with 60 mg of prednisolone.
Carry out an infusion with intravenous drip of 400 ml of rheopolyglucin ♠, 400 ml of isotonic sodium chloride solution. Add 5,000 action units (IU) of heparin in dextran solution ♠ to the dropper, prednisolone at the rate of 10 mg/kg (the entire dose is administered in fractions over 2 hours), 2 ml of 0.25% droperidol solution, 1 ml of 0.05% solution strophanthin.
Subcutaneously inject 2 ml of a 10% caffeine solution, 2 ml of a 25% cordiamine solution ♠.
Provide oxygen continuously throughout treatment.
Severe anaphylactic shock often determines the need for a set of measures in the intensive care unit:
Anticonvulsant treatment;
Correction of disturbances in water-electrolyte metabolism and acid-base balance;
Intubation or tracheostomy;
Mechanical ventilation, etc.
Serum sickness develops 6-12 days after administration of the serum. It manifests itself as a febrile reaction, the appearance of a maculopapular rash on the skin, swelling of the mucous membranes, and lymphadenitis.
Double anaphylactic reaction proceeds in 2 stages:
First, anaphylactic shock develops;
Then - serum sickness.
In the treatment of some infections, it plays a significant role. nonspecific immunotherapy. Its arsenal includes normal human immunoglobulin, immunostimulants and immunosuppressants. They are prescribed to increase the body's nonspecific resistance and have a regulatory effect on the immune system. In the treatment of a number of viral infections (influenza, viral encephalitis, herpes infection), IFN and stimulators of their production are used.
Pentoxyl ♠, methyluracil ♠ and potassium orotate are also used to stimulate leukopoiesis. Splenin ♠ and apilac ♠ speed up recovery after severe infections.
Immunomodulators levamisole, thymalin ♠, T-activin ♠, sodium nucleinate and some lipopolysaccharides (pyrogenal ♠, prodigiosan ♠) help regulate processes cellular immunity and phagocytosis.
It is necessary to pay attention to the fact that the indications for prescribing drugs of this group are determined by a whole complex of various factors:
Features of the pathogenesis of the disease;
The timing and severity of the illness;
The state of nonspecific and specific factors of the body's defense.
Therefore the application immunotropic drugs recommended only under dynamic immunological control.
Pathogenetic treatment aimed at correcting homeostasis disorders in infectious diseases.
His methods and means are based on a detailed study of pathogenetic mechanisms:
Intoxication;
Disorders of water-electrolyte metabolism and acid-base balance;
Changes in the rheological properties of blood;
Microcirculation;
Immune status, etc.
One of the main directions of pathogenetic treatment of infectious diseases is the use of drugs that reduce intoxication. Colloidal solutions have pronounced detoxification properties - hemodez ♠, polydez ♠, rheopolyglucin ♠, macrodex Ψ, gelatinol ♠, albumin and many others, administered intravenously in medium doses of 200 to 400 ml. The detoxification effect of 5% or 10% glucose solution ♠, 0.9% sodium chloride solution is less pronounced. In the treatment of acute intestinal infections accompanied by diarrhea, detoxification can be enhanced by simultaneous administration of intravenous infusions and oral administration of non-steroidal anti-inflammatory drugs (indomethacin) and enterosorbents (enterodeza ♠, Polysorb ♠, activated carbon and etc.). Simultaneously with detoxification, saluretics (furosemide, Lasix ♠, etc.) are prescribed to improve the excretory capacity of the kidneys.
In case of severe infectious diseases, extracorporeal detoxification methods are used:
Hemodialysis;
Hemosorption;
Plasmapheresis;
Cytopheresis.
Indispensable drugs for the correction of dehydration, acid-base balance, rheological and microcirculatory disorders are polyionic crystalloid isotonic solutions for intravenous infusions (Trisol ♠, Quartasol ♠, Laktasol Ψ, etc.) and glucose-saline solutions for oral use (Rehydron ♠, Oralit Ψ, citroglucosolan Ψ ). Their use simultaneously helps reduce intoxication, since the use colloidal solutions in conditions of dehydration is contraindicated. The multidirectional activity of this group of drugs (rehydration and detoxification) is potentiated in acute intestinal infections by the simultaneous administration of prostanoid biosynthesis inhibitors (indomethacin).
To prevent severe manifestations of inflammation and allergies in many infectious diseases (encephalitis, meningitis, infectious mononucleosis, brucellosis, trichinosis, etc.), antihistamines and glucocorticoids (prednisolone, dexamethasone, hydrocortisone, etc.) are prescribed. Hormonal drugs are especially indicated in cases of ITS and development acute failure adrenal glands (meningococcal infection, diphtheria), as well as anaphylactic shock.
Infectious diseases, especially intestinal infections, often complicates the development of dysbiosis (dysbacteriosis), which is greatly facilitated by active and long-term, but necessary treatment antibiotics.
Probiotics are widely used in the correction of dysbiosis, i.e. bacterial preparations that restore and regulate intestinal microflora (colibacterin ♠, bifidumbacterin ♠, lactobacterin ♠, bactisubtil ♠, etc.), and prebiotics (substances of non-microbial origin).
Regulation of the processes of proteolysis, fibrinolysis, depolymerization in the pathogenetic treatment of infectious diseases is carried out by prescribing enzyme preparations. In recent years, trypsin, chymotrypsin, fibrinolysin, streptodecase ♠, ε-aminocaproic acid, deoxyribonuclease ♠, etc. have been widely used. A special place is occupied by proteolysis inhibitors (contrical ♠, trasylol ♠ and their analogues), recommended for acute massive liver necrosis (in severe and complicated course of acute viral hepatitis). The need to correct disorders of the secretion of gastrointestinal glands explains the advisability of using pancreatin, festal ♠, panzinorm ♠, mezim ♠, pankurmen Ψ and other enzyme preparations.
An obligatory component in the treatment of infectious patients is vitamin therapy. A lack of vitamins reduces the body's resistance and facilitates the development of the infectious process, often manifested by an increase in intoxication, the development of an unfavorable course of the disease and complications. Prescribing vitamins C and group B to infectious patients helps normalize metabolic processes, reduce intoxication, and has a positive immunomodulatory effect.
Widely used in infectious diseases symptomatic treatment- prescription of cardiovascular and antispasmodic drugs, painkillers, antipyretics, sedatives, hypnotics, anticonvulsants, etc.
In case of severe infectious diseases and the development of complications (ITSH, thrombohemorrhagic syndrome, cerebral edema, acute respiratory and cardiovascular failure, convulsive syndrome, acute liver failure and acute renal failure) intensive complex pathogenetic treatment is indicated using the above and special treatment methods (ventilation, hyperbaric oxygenation, etc.). Treatment is often carried out in intensive care units.
According to individual indications, methods of physiotherapy and balneotherapy are used for infectious diseases.
After many infectious diseases, dispensary observation of convalescents, as well as sanatorium treatment, is recommended.
Infection (lat. Infectio– infect) is a state of infection caused by the interaction of an animal organism and a pathogenic microbe. The proliferation of pathogenic microbes that have entered the body causes a complex of pathological and protective-adaptive reactions, which are a response to the specific pathogenic effect of the microbe. The reactions are expressed in biochemical, morphological and functional changes, in the immunological response and are aimed at maintaining the constancy of the internal environment of the body (homeostasis).
The state of infection, like any biological process, is dynamic. The dynamics of interaction reactions between micro- and macroorganisms is called the infectious process. On the one hand, the infectious process includes the introduction, reproduction and spread of the pathogen in the body, its pathogenic action, and on the other hand, the body’s reaction to this action. The body's responses, in turn, are divided conditionally into two groups (phases): infectious-pathological and protective-immunological.
Consequently, the infectious process constitutes the pathogenetic essence of an infectious disease.
The pathogenic (harmful) effect of the infectious agent in quantitative and qualitative terms may be different. In specific conditions, it manifests itself in some cases in the form of an infectious disease of varying severity, in others - without pronounced clinical signs, in others - only changes detected by microbiological, biochemical and immunological research methods. This depends on the quantity and quality of the specific pathogen that has penetrated the susceptible organism, the conditions of the internal and external environment that determine the resistance of the animal and the nature of the interaction between the micro- and macroorganism.
Based on the nature of the interaction between the pathogen and the animal organism, three forms of infection are distinguished.
The first and most striking form of infection is an infectious disease. It is characterized external signs disturbances in the normal functioning of the body, functional disorders and morphological tissue damage. An infectious disease manifested by certain clinical signs is classified as an overt infection. Often, an infectious disease is not clinically manifested or manifests itself unnoticeably, and the infection remains hidden (asymptomatic, latent, inapparent). However, in such cases, with the help of bacteriological and immunological studies, it is possible to identify the presence of an infectious process characteristic of this form of infection - disease.
The second form of infection includes microbial carriage that is not associated with the animal’s previous illness. In such cases, the presence of an infectious agent in the organs and tissues of a clinically healthy animal does not lead to pathological condition and is not accompanied by immunological restructuring of the body. When carrying microorganisms, the established balance between micro- and macroorganisms is maintained by natural resistance factors. This form of infection can only be determined through microbiological testing. Microbial carriage is quite often recorded in many diseases among healthy animals of both susceptible and non-susceptible species (causative agents of swine erysipelas, pasteurellosis, clostridiosis, mycoplasmosis, catarrhal fever, etc.). In nature, there are other types of microbial carriage (for example, by convalescents and recovered animals), and they must be differentiated from an independent form of infection - microbial carriage by healthy animals.
The third form of infection includes an immunizing subinfection, in which microbes that enter the animal’s body cause only specific changes and immunity, but the pathogens themselves die. There are no functional disorders in the body and it does not become a source of infectious agents. The immunizing subinfection, like microbial carriage, is widespread in nature, but has not yet been sufficiently studied (for example, with leptospirosis, emkar, etc.), so it is difficult to control when implementing anti-epizootic measures.
Thus, the concept of “infection” is much broader than the concept of “infectious process” and “infectious disease”. A differentiated approach to forms of infection makes it possible to correctly diagnose infectious diseases and identify infected animals in a troubled herd as much as possible.
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Chapter 1. Infection, infectious process, infectious disease
Infectious diseases are widespread throughout the world and are caused by various microorganisms. “Contagious” diseases have been known since ancient times; information about them can be found in ancient monuments writing: in the Indian Vedas, the works of Ancient China and Ancient Egypt. Descriptions of some infectious diseases, such as dysentery, tetanus, erysipelas, anthrax, viral hepatitis, etc., can be found in the writings of Hippocrates (460-377 BC). In Russian chronicles, infections were described under the name of epidemics, endemic pestilences, emphasizing the main feature - massiveness, high mortality and rapid spread among the population. Devastating epidemics and pandemics of infectious diseases were described. It is known that in the Middle Ages a plague epidemic (“Black Death”) raged, from which a third of the population of Europe died out, and throughout the world from the plague in the 14th century. More than 50 million people died. During the First World War, there was a flu pandemic (“Spanish flu”), which affected 500 million people, 20 million of them died. Long time nothing was known about the cause of infectious diseases; it was believed that these diseases arise in connection with “miasmas” - poisonous fumes in the air. This is the teaching in the 16th century. was replaced by the doctrine of “contagia” (Frakstoro). In the XVII-XIX centuries. Many childhood infections were described, such as measles, chickenpox, scarlet fever, etc. The full flowering of the study of infectious diseases occurred in the 19th century. during the period of rapid development of microbiology and the emergence of immunology in the twentieth century. (L. Pasteur, R. Koch, I. I. Mechnikov, L. Erlich, G. N. Minkh, D. K. Zabolotny, L. A. Zilber). Advances and achievements in microbiology contributed to the identification of infectious diseases as an independent science and the further development of teachings about the etiology, pathogenesis, symptoms, treatment and prevention of infectious diseases. Contribution to the development of infections childhood contributed by the works of A. A. Koltypin, M. G. Danilevich, D. D. Lebedev, M. S. Maslov, S. D. Nosov and other scientists.
Infectious diseases are a large group of human diseases that arise as a result of exposure to viruses, bacteria and protozoa. They develop through the interaction of two independent biosystems - a macroorganism and a microorganism under the influence of the external environment, and each of them has its own specific biological activity.
Infection is the interaction of a macroorganism with a microorganism under certain conditions of the external and social environment, as a result of which pathological, protective, adaptive, compensatory reactions develop, which are combined into an infectious process. The infectious process is the essence of an infectious disease and can manifest itself at all levels of organization of the biosystem - submolecular, subcellular, cellular, tissue, organ, organism.
However, not every exposure to a pathogen causes disease. An infectious disease occurs when there is a disruption in body function and the appearance of a clinical picture. Thus, an infectious disease is an extreme degree of development of the infectious process. If, upon penetration of the pathogen into the body, a clinical picture does not form, then they speak of a healthy carriage, which can happen in children with residual specific immunity or in people with congenital natural immunity. There is also convalescent carriage, which occurs during the period of recovery from an infectious disease. Depending on the conditions of infection, the properties of the infectious agent, the state of the macroorganism (susceptibility, degree of specific and nonspecific reactivity), several forms of interaction of the microorganism with the human body have been described.
Manifest forms (manifested clinically) are divided into acute and chronic. There are also typical, atypical and fulminant forms, which usually end in death. Based on severity, they are divided into mild, moderate and severe forms.
In the acute form of a clinically manifested infection, the pathogen remains in the body for a short time. This form is characterized by a high intensity of release of pathogens into the environment by patients, which creates a high infectiousness of patients. Many infectious diseases occur in acute form, for example plague, smallpox, scarlet fever. Others, both acute and chronic, include brucellosis, hepatitis B, and dysentery.
The chronic form of the disease is characterized by a longer stay of the pathogen in the body, frequent exacerbations and remissions of the pathological process, and in the case of timely treatment- favorable outcome and recovery, as in the acute form.
Repeated illness due to infection with the same infectious agent is called reinfection. If infection with another infectious agent occurs before recovery from the disease, then they speak of superinfection.
Bacterial carriage is a process that occurs asymptomatically in acute or chronic form. Pathogens are present in the body, but the process does not manifest itself, and outwardly the person remains healthy. Immunological changes are detected in the body, as well as functional morphological disorders in organs and tissues, typical for this disease.
The subclinical form of infection is of great epidemiological significance, since such patients are a reservoir and source of pathogens with preserved ability to work and social activity, which complicates the epidemic situation. However, the high frequency of subclinical forms of some infections (dysentery, meningococcal infection, influenza, etc.) contributes to the formation of a massive immune layer among people, which to a certain extent stops the spread of these infectious diseases.
Overlatent (latent) infection occurs as a result of long-term asymptomatic interaction of a macroorganism with a microorganism. At its core, it is a chronic infectious disease with a benign course; it occurs in diseases such as hepatitis B, herpetic infection, typhoid fever, cytomegalovirus infection and many others. etc. This form is more common in children with reduced cellular and humoral immunity, while the infectious agent is either in a defective state or in a special stage of its life activity (L - form). The formation of L - forms occurs under the influence of the body’s protective immune forces and medications (antibiotics). Atypical strains are formed with changes in all properties of the microorganism.
A significantly new form of interaction between infection and the human body is slow infection. It is characterized by a long (up to several years) incubation period - a stage at which there is no disease. At the same time, the disease steadily progresses with the development of severe disorders in many organs and systems (most often in the nervous system), and death is often observed. This type of infection includes: AIDS, congenital rubella, chronic active hepatitis with transition to cirrhosis, etc.
Infectious diseases resulting from infection by microorganisms of one type are called monoinfections. When infected with bacteria different types- mixed, or mixed infection. One of the variants of a mixed infection is a secondary infection, in which a new one is added to an existing disease.
The infectious process can occur due to the activation of saprophytic microflora, i.e. those microbes that constantly live on the skin and mucous membranes. In these cases, we talk about endogenous or autoinfection, which most often occurs in weakened children with chronic diseases, in children who have been receiving antibacterial or cytostatic (immune suppressive) therapy for a long time.
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Part I. Infectious diseases. basic conceptsChapter 2. Causative agent of an infectious disease
Infection(Latin infectio - infection) is a set of biological processes that arise and develop in the body when pathogenic microbes are introduced into it.
The infectious process consists of the introduction, reproduction and spread of the pathogen in the body, its pathogenic action, as well as the reaction of the macroorganism to this action.
There are three forms of infection:
1. An infectious disease characterized by disruption of the normal functioning of the animal body, organic, functional disorders and morphological damage to tissues. An infectious disease may not be clinically apparent or may be subtle; then the infection is called hidden, latent. In this case, the infectious disease can be diagnosed using various additional methods research.
2. Microcarriage not associated with the animal becoming ill. The balance between the micro- and macroorganism is maintained due to the resistance of the macroorganism.
3. An immunizing infection is a relationship between a micro- and macroorganism that causes only a specific restructuring in the immune system. There are no functional disorders; the animal body is not a source of the infectious agent. This form is widespread, but not well studied.
Commensalism- a form of cohabitation when one of the organisms lives at the expense of the other, without causing him any harm. Commensal microbes include representatives of the normal microflora of an animal. When the body's resistance decreases, they can also exhibit a pathogenic effect.
Mutualism- a form of symbiosis when both organisms derive mutual benefit from their cohabitation. A number of representatives of the normal microflora of animals are mutualists that benefit the owner.
Factors of pathogenicity of microorganisms are divided into two groups, which determine:
invasiveness of microorganisms- the ability of microorganisms to penetrate through immunological barriers, skin, mucous membranes into tissues and organs, multiply in them and resist the immune forces of the macroorganism. Invasiveness is due to the presence of a microorganism capsule, mucus that surrounds the cell and resists phagocytosis, flagella, pili, responsible for attaching microorganisms to the cell, and the production of enzymes hyaluronidase, fibrinolysin, collagenase, etc.;
toxicogenicity- the ability of pathogenic microorganisms to produce exo- and endotoxins.
Exotoxins- products of microbial synthesis released by the cell into the environment. These are proteins with high and strictly specific toxicity. It is the action of exotoxins that determines the clinical signs of an infectious disease.
Endotoxins are part of the cell wall of bacteria. They are released when the bacterial cell is destroyed. Regardless of the producing microbe, endotoxins cause the same type of pathological process: weakness, shortness of breath, diarrhea, and hyperthermia develop.
The pathogenic effect of viruses is associated with their reproduction in the cell of a living organism, leading to its death or the elimination of its functional activity, but an abortive process is also possible - the death of the virus and the survival of the cell. Interaction with the virus can lead to cell transformation and tumor formation.
Each infectious agent has its own spectrum of pathogenicity, i.e. a circle of susceptible animals where microorganisms realize their pathogenic properties.
There are obligate pathogenic microbes. The ability to cause an infectious process is their constant species characteristic. There are also facultatively pathogenic (opportunistic) microorganisms, which, being commensals, cause infectious processes only when the resistance of their host weakens. The degree of pathogenicity of microorganisms is called virulence. This is an individual feature of a specific, genetically homogeneous strain of microbe. Virulence may vary depending on the living conditions of microorganisms.
In the case of acutely infectious diseases, when infectious agents enter the body of a hardy animal, as a rule, the animal becomes ill.
Such pathogens fully satisfy the three conditions of the postulate of Henle and Koch:
1. The pathogenic microbe must be detected in a given disease and not occur either in healthy people or in patients with other diseases.
2. The pathogenic microbe must be isolated from the patient’s body in its pure form.
3. A pure culture of the isolated microbe should cause the same disease in a susceptible animal.
Currently, this triad has largely lost its significance.
A certain group of pathogens does not satisfy Koch's triad: they are isolated from healthy animals and from patients with other infectious diseases. They are low virulent, and experimental reproduction of the disease in animals is not possible. The causal role of these pathogens is difficult to establish.
Types of infection. Depending on the method of infection, the following types of infection are distinguished:
exogenous - the infectious agent enters the body from the environment;
endogenous, or autoinfection, occurs when the body’s protective properties are weakened and the virulence of opportunistic microflora increases.
Depending on the distribution of microorganisms in the body of animals, the following types of infection are distinguished:
local, or focal, infection - the causative agent of the disease multiplies at the site of introduction into the body;
generalized - the causative agent of the disease spreads from the site of introduction throughout the body;
toxic infection - the pathogen remains at the site of entry into the body, and its exotoxins enter the blood, having a pathogenic effect on the body (tetanus, infectious enterotoxemia);
toxicosis - exotoxins of microorganisms enter the body with food, they play the main pathogenetic role;
bacteremia/viremia - pathogens from the site of entry enter the blood and are transported by blood and lymph to various organs and tissues multiply there too;
septicemia/sepsis - the proliferation of microorganisms occurs in the blood, and the infectious process is characterized by contamination of the entire body;
pyaemia - the pathogen spreads by lymphogenous and hematogenous routes into the internal organs and multiplies in them not diffusely (bacteremia), but in separate foci, with the accumulation of pus in them;
Septicopyemia is a combination of sepsis and pyemia.
The pathogen can cause various forms of infectious disease depending on the routes of penetration and spread of microbes in the body of animals.
Dynamics of the infectious process. Infectious diseases differ from non-contagious diseases in specificity, contagiousness, stages of progression and the formation of post-infectious immunity.
Specificity - infectious disease causes certain type microorganism
Contagiousness is the ability of an infectious disease to spread by transferring the pathogen from a sick animal to a healthy one.
The staged course is characterized by incubation, prodromal (preclinical) and clinical periods, the outcome of the disease.
The period from the moment the microbe enters the animal’s body until the first symptoms of the disease appear is called incubation. It varies and ranges from one or two days (influenza, anthrax, botulism) to several weeks (tuberculosis), several months and years (slow viral infections).
During the prodromal period, the first nonspecific symptoms of the disease appear - fever, anorexia, weakness, depression, etc. Its duration ranges from several hours to one or two days.
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