Staphylococci are ubiquitous microorganisms that cause various purulent-inflammatory processes in humans and animals (they are also called pyogenic ).
Characteristics of pathogens.
Staphylococcus belong to the department Firmicutes, sem. Micrococcaceae, family Staphylococcus. The genus includes 27 species, among which there are pathogenic, opportunistic species and saprophytes. The main human lesions are caused by 3 types: S. aureus, S. epidermidisAndS. saprophyticus.
Morphology: have a spherical shape (round cells are called cocci). In preparations from pure culture they are located in the form of random clusters, reminiscent of bunches of grapes. In smears of pus - singly, in pairs or in small groups. They do not have spores or flagella (motile) and can form a delicate capsule.
Tincorial properties: gram "+".
Cultural properties: facultative anaerobes, not demanding on nutrient media, on solid media they form S-shaped colonies - round, with a smooth edge, colored cream, yellow, Orange color, in liquid media they give uniform turbidity. Grows in saline media (5 – 10% NaCCl); milk-salt and yolk-salt agar – elective environments for staphylococci.
Biochemical properties: saccharolytic – break down 5 carbohydrates of Hiss media to acid; proteolytic – proteins are broken down to form H 2 S, gelatin is liquefied in the form of a funnel, on day 4-5 the funnel is filled with liquid.
Antigenic structure: have about 30 antigens: proteins, polysaccharides, teichoic acids; many extracellular substances that form staphylococci have antigenic properties.
Pathogenicity factors: A) exotoxin (released outside the cell), consisting of several fractions: hemolysin (destroys red blood cells) leukocidin (destroys leukocytes), lethal toxin (kills rabbits) necrotoxin (causes skin necrosis in rabbits when administered intradermally), enterotoxin (causes food poisoning), exfoliatin (causes pemphigus in newborns - “scalded skin” syndrome); b) aggression enzymes: hyaluronidase (destroys hyaluronic acid), plasmacoagulase (clottes blood plasma) DNase (destroys DNA) lecitovitellase (destroys lecithin), fibrinolysin (destroys fibrin clots).
Resistance: resistant in the external environment, but sensitive to disinfection. solutions, especially brilliant green, are often resistant to penicillin, because they form the enzyme penicillinase.
Epidemiology of staphylococcal infections.
Staphylococci are ubiquitous and are often part of the normal human microflora (carriers). Staphylococcus aureus inhabits the nasal passages, abdominal cavity, and axillary areas. Staphylococcus epidermidis colonizes smooth skin and the surface of mucous membranes. Saprophytic staphylococcus colonizes the skin of the genitals and the mucous membrane of the urinary tract.
Staphylococcal infections are called the plague of the 20th century, i.e. they are dangerous and very common, especially in maternity hospitals and surgical departments.
source of infection– a sick person or a healthy carrier;
transmission mechanism– mixed;
transmission routes: airborne, airborne, dusty, contact, foodborne;
population receptivity– depends on general condition and age; Newborns and infants are most susceptible.
Most infections are endogenous in nature and infection is associated with the transfer of the pathogen from places of colonization to a traumatized (damaged) surface.
Pathogenesis and clinical picture of diseases.
Entrance gate – any organ and any tissue; staphylococci penetrate through damaged skin, mucous membranes mouth, respiratory tract, genitourinary system, etc.
Staphylococci multiply at the site of penetration, form exotoxin and aggressive enzymes and cause the formation of local purulent-inflammatory foci. Staphylococci spreading from these foci can enter the blood (sepsis), and from the blood. – to other organs (septicopyemia).
Incubation period– from several hours to 3 – 5 days.
Staphylococci cause more than 100 nosological forms of diseases. They affect the skin (boils, carbuncles), subcutaneous tissue (abcesses, phlegmons), Airways(angina, pneumonia, sinusitis), cause mastitis, purulent myositis and muscle abscesses, brain abscesses after traumatic brain injuries, endocarditis, affect bones (osteomyelitis, arthritis), liver, kidneys, urinary tract (pyelonephritis, cystitis). Diseases are especially dangerous when staphylococci penetrate the blood (sepsis) and affect internal organs (septicemia). Staphylococcal infections are accompanied by intoxication, fever, and headache.
The diseases are acute, but can also be chronic.
Scalded baby syndrome observed in newborns. The disease begins rapidly, characterized by the formation of large foci of erythema on the skin with the formation of large blisters (as with thermal burns) and the exposure of weeping eroded areas.
Toxic shock syndrome first registered in 1980 in women 15–25 years old using tampons during menstruation. It is manifested by high temperature (38.8 ° C and above), vomiting, diarrhea, rash, drop in blood pressure and the development of shock, often leading to death.
Food poisoning manifested by vomiting, watery diarrhea within 2 – 6 hours. after eating infected foods, usually pastries with cream, canned food, meat and vegetable salads. The symptoms disappear or are significantly reduced after 24 hours, even without treatment.
Immunity: weak, allergies to staphylococcal toxins often develop, which leads to long-term, chronic diseases.
Laboratory diagnostics.
Test material: pus, discharge from wounds, sputum, blood, vomit, food products.
Diagnostic methods:
bacterioscopic – a smear is prepared from the pus, stained with Gram and examined under a microscope; the smear shows leukocytes, neutrophils, individual round staphylococcal cells and random clusters resembling a bunch of grapes (a smear is not prepared from blood);
bacteriological - allocate pure culture, inoculating the material on nutrient media (usually blood agar to detect hemolysis), and then carry it out identification – study morphology (Gram stain), the presence of pathogenicity factors (plasmocoagulase, lecitovitellase) and biochemical properties (anaerobic breakdown of mannitol and glucose); definition is mandatory antibiograms; staphylococci are representatives of normal microflora, therefore one cannot limit oneself to the isolation and identification of the pathogen; quantitative methods analysis - definition number of microbes in the sample;
bioassay (at food poisoning) - they infect small suckling kittens, who within an hour develop vomiting, diarrhea and die.
Serological tests were not used.
Treatment.
Apply antibiotics wide spectrum of action, semisynthetic penicillins(methicillin, oxacillin), sulfa drugs . An antibiogram must be determined. IN last years Staphylococci resistant to most chemotherapy drugs are isolated from patients. In such cases, they are used for treatment antitoxic antistaphylococcal plasma or immunoglobulin, obtained from the blood of donors immunized with staphylococcal toxoid. At chronic forms diseases, staphylococcal toxoid is also administered, and an autovaccine is used.
Prevention.
For specific prevention(planned surgical patients, pregnant women) adsorbed staphylococcal toxoid may be used.
Nonspecific prevention has more important– this is compliance with sanitary and hygienic rules, hardening the body.
Inflammation palatine tonsils With acute course often provoked by various pathogenic organisms, among which Staphylococcus aureus is present. What is the pathogen Staphylococcus, what features does it differ from and where does it come from in the human body?
All types of staphylococci have the same round shape, lead a sedentary existence, and prefer to form groups that resemble a bunch of grapes. They are present in the air, soil, microflora of the human body and even on everyday objects that are familiar to us, which is also characteristic of another fungal organism -.
Infection pathogenic microorganism carried out directly upon contact of a staphylococcus carrier with a healthy person.
Staphylococcus
Today, the genus of staphylococci is divided into 3 main types:
- Staphylococcus epidermidis.
- Staphylococcus saprophytic.
- Staphylococcus aureus.
The causative agent of sore throat, Staphylococcus, is found on skin and mucous membranes of every person of any age group.
In case of active manifestation of the bacterium, the development of many severe diseases is observed:
- Purulent lesions on the skin.
- Sepsis.
- Meningitis.
- Staphylococcal tonsillitis (chronic tonsillitis) and a number of other pathologies.
It should be emphasized that A sore throat (sore throat) can be caused by Staphylococcus aureus. According to statistics, almost 20% of people are permanent carriers of this microbe. True, most types of staphylococcus are peaceful inhabitants of human skin, and only the golden variety shows increased aggression towards its host.
It develops immunity to antibiotics amazingly quickly, which is why we have to systematically search for and develop more and more new antibacterial drugs.
Opened in due course penicillin was effective means against Staphylococcus aureus, however, to date this antibiotic is not able to fully suppress the bacterium.
According to scientists, the haphazard use of antibiotics without a doctor’s prescription, or non-compliance with their dosage regimen, contributes to the fact that the microorganism becomes increasingly resistant to drugs of this type, that is, a person involuntarily contributes to the breeding of its new strains.
Features of staphylococcal sore throat
Signs of staphylococcal tonsillitis are similar to the symptomatic picture viral sore throat
Staphylococcal sore throat– a consequence of damage to the human body by the pathogen Staphylococcus. Signs of staphylococcal infection are very similar to the symptomatic picture of viral sore throat. Hidden Development illness lasts several days, then manifests itself acutely and with the following symptoms:
- General intoxication of the body.
- Increased body temperature, which is also typical for.
- Soreness and enlargement of the cervical and submandibular lymph nodes.
- Vomit.
- Severe sore throat when swallowing.
- Hyperemia and swelling of the tonsils.
- Formation of purulent ulcers and plaque on the tonsils.
- Swelling and inflammation of the palate, back wall throat.
In case of untimely treatment, Staphylococcal tonsillitis can lead to the following pathological complications:
- Pleurisy.
- Sepsis.
- Pneumonia, which is also typical for such an organism as.
- Tonsillitis.
- Myocarditis.
- Glomerulonephritis.
- Endocarditis.
- Pericarditis.
- Heart disease.
A high percentage of manifestations of staphylococcal sore throat is noted during seasonal epidemics of viral and infectious diseases, as well as with a decrease in the protective abilities of the immune system.
Many patients are interested in whether this pathogenic agent can lead to pathological complications such as tuberculosis or cholera?
note that many pathogenic microbes are involved in the development of such life-threatening diseases as cholera and tuberculosis.
The causative agents of cholera are:
- Cocchi.
- Staphylococci.
- Bacilli.
- Vibrios.
Staphylococcus aureus - common cause of development food diseases. The fact is that it produces enterotoxin - a toxic substance that provokes severe diarrhea, abdominal pain and vomiting. Staphylococcus multiplies well in food products, especially meat and vegetable salads, in butter creams, canned food. Spoiled food accumulates a toxin that leads to illness.
Staphylococcus aureus
The causative agents of tuberculosis are:
- Spirilla.
- Cocchi.
- Bacilli.
- Staphylococci.
As we see, staphylococcus is a rather serious and dangerous microorganism, to combat which you will need competently prescribed therapy and strict adherence to all instructions prescribed by the doctor.
Therapy for chronic tonsillitis
How is staphylococcal sore throat treated? First of all a thorough examination of the throat swab will be required with further sowing and cultivation of the bacterium – the culprit of the disease – on a nutrient medium.
This method is very important, since it helps to establish the state of the microflora, the degree of sensitivity of a conditionally pathogenic organism to many antibacterial drugs, allowing you to choose for treatment best option medicine.
The following results are also significant:
- Nasal swab.
- Throat swab.
- Sputum culture.
- Urine, feces and blood tests.
- Serological technique.
- Special tests.
Amoccillin
Therapeutic therapy begins with drugs related to protected penicillins, for example, Sulbactam, Amoxicillin and others. Medicines are popular soluble form, among which we can name Flemoxiclav solutab. The simultaneous use of penicillins with clavulanic acid helps to reduce the resistance of bacteria to antibacterial drugs.
Today, to eliminate staphylococcal infections, modern medicine offers such medicines:
- Oxacillin.
- Vancomycin.
- Linezolid.
When prescribing antibiotics, the doctor recommends a number of accompanying procedures, for example, gargling with local antiseptics, taking vitamins, minerals, dietary supplements. To eliminate intoxication it is useful for the patient drinking plenty of fluids . In case of severe form of the disease, prescribed intravenous injections isotonic drugs.
The treatment course for staphylococcal sore throat lasts about four weeks, until tests confirm the complete elimination of the bacterium from the patient’s body.
Vancomycin
To successfully get rid of the disease, Doctors do not recommend resorting to self-medication or violating the therapeutic course.
Staphylococci can instantly develop resistance to antibiotics.
Modern medicine distinguishes the carrier pathogenic staphylococcus from tonsillitis.
In the first case, no signs of the disease are observed and no therapeutic intervention is required.
Conclusion
Always remember, development is like this dangerous pathology, like staphylococcal sore throat, is a signal that your immune system is weakened and needs to increase its protective functions.
At the slightest suspicion of infection, be sure to consult a doctor, which will help avoid complications that adversely affect normal work organs and systems of the human body.
In contact with
Laboratory diagnosis of coccal infections. Staphylococci.
Laboratory diagnosis of streptococcal infections.
Neisseria.
Causative agents of bacterial intestinal infections: Escherichiosis, typhoid fever, paratyphoid.
Laboratory diagnosis and prevention of bacterial dysentery.
Laboratory diagnosis and prevention of cholera.
Microorganisms that have a spherical shape (cocci) are among the most ancient on Earth. They are quite widespread in nature. According to the latest classification of bacteria by Bergi (1986), coccal microbes are divided into three families:
1. Micrococcaceae (micrococci, staphylococci, tetracocci, sarcini).
2. Deinococcaceae (streptococci, peptococci, peptostreptococci).
3. Neisseriaceae (Neisseria, Veillonella).
Characteristic common feature pathogenic cocs is their ability to cause inflammatory processes with the formation of pus. In this regard, they are often called pyogenic (pyogenic) cocci. Highest value in human infectious pathology include staphylococci, streptococci and neisseria.
Staphylococcus (Staphylococcus)
Pathogenic staphylococcus was first discovered by L. Pasteur in 1880. Its properties were described in more detail by F. Rosenbach (1884).
Morphology and physiology. Staphylococci have a regular round shape with a size of 0.5 - 1.5 microns
The smears are arranged in irregular clusters that resemble bunches of grapes
When making smears from pus, there may not be a typical arrangement of cells. Staphylococci are gram-positive, nonmotile, do not form spores, individual species They have a delicate capsule in the body. The cell wall contains peptidoglycan (murein) and teichoic acids.
Staphylococci are facultative anaerobes and grow best under aerobic conditions. They are unpretentious to nutrient media and grow well on simple media. On MPA, the colonies are regular round in shape, convex, opaque, with a smooth and shiny, as if polished surface, colored golden, fawn, white, lemon yellow, depending on the color of the pigment.
On blood agar, colonies are surrounded by a zone of hemolysis.
In MPB they cause turbidity and sediment at the bottom. In bacteriological laboratories, staphylococci are often cultivated on media with 7-10% sodium chloride. Other bacteria cannot withstand such a high salt concentration. Therefore, salt agar is a selective medium for staphylococci.
Staphylococci secrete proteolytic and saccharolytic enzymes. They liquefy gelatin, cause milk to shrink, and ferment a number of carbohydrates, releasing acid.
Toxin formation. Staphylococci, especially Staphylococcus aureus, produce exotoxins and many “aggression enzymes” that are important in the development of staph infections. Their toxins are quite complex. Many variants of hemotoxin, leukocidins, necrotoxins, and lethal toxin are described. Yes, alpha, beta, gama and hemolysin - delta are currently known, which causes hemolysis of erythrocytes in humans and many animal species. Leukocidins destroy leukocytes, macrophages and other cells, and in lower concentrations suppress their phagocytic function. Necrotoxin causes skin necrosis, and a lethal toxin intravenous administration- almost instant death. Staphylococcus aureus produces exfoliatins, which cause impetigo in children and pemphigus in newborns. Certain species are capable of secreting enterotoxins that specifically act on intestinal enterocytes, which leads to the occurrence of foodborne toxic infections and enterocolitis. Six varieties of enterotoxins have been described (A, B, C, D, E, F), which are relatively simple proteins.
In the pathogenic action of staphylococci, in addition to toxins, aggression enzymes are important: plasmacoagulase, fibrinase, deoxyribonuclease, hyaluronidase,
proteinase, gelatinase, lipase, and the like. They are a stable feature of individual species. When determining individual of them (coagulase, hyaluronidase, DNAase), the question of the type and virulence of the isolated cultures is decided. Protein A is important in the manifestation of the pathogenic properties of staphylococci. It is capable of reacting with IgG. The protein A+IgG complex inactivates complement, reduces phagocytosis, and causes platelet damage.
In recent years, the issue of the pathogenicity of staphylococci has been debated. Some scientists classify them as opportunistic bacteria, while others convincingly argue that non-pathogenic staphylococci do not exist. Now the latter theory is dominant. The occurrence of diseases in end result depends on the body's immune reactivity.
People sensitive to staphylococci, large and small cattle, horses, pigs, and among laboratory animals - rabbits, mice, kittens .
Antigens and classification.
The antigenic structure of staphylococci is quite complex and variable. Nearly 30 antigens associated with proteins, teichoic acids, and polysaccharides have been described. The main one is capsular protein A.
The genus Staphylococcus includes 29 species, but not all of them cause disease in humans. Currently, bacteriological laboratories in Ukraine identify only three species: S. aureus, S. epidermidis, S. saprophyticus. Tests have been developed to identify eight more species.
Ecology and distribution. The main biotopes of staphylococci in the host body are the skin, mucous membranes and intestines. They are part of the normal microflora of the human body and are in symbiosis with it. However, when staphylococcal infections occur, other organs and tissues can be affected. Staphylococci enter our environment from sick people and animals and carriers. They are constantly found in the air, water, soil, and on a variety of consumer items. Upon contact with sick individuals, resident staphylococcal bacteria carriers can form, when the nasal mucosa becomes their permanent residence, from where they are released in massive doses. Such carriage is especially dangerous among hospital medical personnel, since carriers can become a source of hospital-acquired infections.
Staphylococci are quite persistent in external environment. At room temperature they survive on nursing supplies for 1-2 months. When boiled they die instantly, at 70-80 °C - after 30 minutes. A chloramine solution (1%) causes their death after 2-5 minutes. Very sensitive to brilliant green, which is widely used in the treatment of purulent skin diseases.
Human diseases. Staphylococci will most often affect the skin, its appendages, and subcutaneous tissue. They cause boils, carbuncles, felons, abscesses, phlegmon, mastitis, lymphadenitis, wound suppuration. They are also isolated for pneumonia, bronchitis, and pleurisy. They can cause tonsillitis, tonsillitis, sinusitis, otitis media, and conjunctivitis. Staphylococci also cause diseases of the nervous system (meningitis, brain abscesses) and of cardio-vascular system(myocarditis, endocarditis). Foodborne illnesses, enterocolitis, and cholecystitis can be very dangerous. When enteringblood or bone marrow cause sepsis and osteomyelitis, respectively. However, all diseases of staphylococcal etiology are not considered highly infectious.
Immunity.
People do not have congenital immunity to staphylococci, but resistance to them is quite high. Despite constant contact with staphylococci, infection occurs relatively rarely. As a result of the infection, immunity develops against the microbes themselves, their toxins, enzymes, and protein A, but it is short-lived.
Laboratory diagnostics.
MaterialBlood, pus, mucus, urine, gastric lavage, feces, and food residues are used for research. Pus is examined by bacterioscopic and bacteriological methods, other materials - by bacteriological methods. After isolating a pure culture, the species is determined by such factors as the ability to decompose glucose and mannitol under anaerobic conditions, the formation of plasma coagulase, hemolysin, DNase, protein A, and the ability to decompose sugars. To identify sources of infection and routes of transmission, especially during disease outbreaks in maternity hospitals and surgical hospitals, phage typing of isolated cultures is carried out using an international set of staphylococcal bacteriophages. The sensitivity of isolated cultures to antibiotics must be determined in order to prescribe rational chemotherapy drugs for treatment.
Prevention and treatment.
Prevention of the occurrence and spread of staphylococcal infections is aimed at identifying and treating carriers of Staphylococcus aureus, especially among medical personnel of maternity hospitals, surgical and children's departments of hospitals. It is necessary to strictly maintain the harsh sanitary regime of work in hospital institutions and systematically carry out disinfection. For the prevention of staphylococcal infections in maternity hospitals, a rational regime of sterilization, pasteurization and preservation is important. breast milk. In industrial enterprises, protective ointments and pastes are used to prevent suppuration due to microtraumas. In order to increase anti-staphylococcal immunity, immunization with staphylococcal toxoid is practiced in persons in whom injuries and microtraumas often occur. In the treatment of acute staphylococcal diseases, antibiotics, sulfonamide and nitrofuran drugs, and miramistin are prescribed. The choice of drugs depends on the results of determining the sensitivity of the isolated culture to them. For the treatment of sepsis, osteomyelitis and other severe staphylococcal infections, immunological drugs are used: staphylococcal immunoglobulin, hyperimmune plasma. For chronic diseases, staphylococcal toxoid and autovaccine are used.
Streptococcus (Streptococcus)
Streptococci were first discovered by T. Billroth in 1874 for wound infections, later L. Pasteur discovered them in sepsis, and F. Rosenbach isolated them in pure culture.
Morphology and physiology.
Streptococci have a round or oval shape with a size of 0.6-1.0 microns, arranged in the form of chains of different lengths, gram-positive, nonmotile, do not have spores,
some species form microcapsules.
The type of respiration is facultative anaerobes, although there are some species with strong anaerobes. The optimal temperature for their cultivation is 37 °C. They do not grow on simple media. They are grown on glucose broth and blood agar.
In liquid media, a precipitate forms, the broth remains transparent. Based on the nature of growth on blood agarestreptococci, they are divided into three types: β-, form hemolysis zones around the colonies; α - opaque greenish zones around the colonies; γ-streptococci.
Isolated colonies are small, translucent, shiny, smooth and shiny, rarely rough. Streptococci are biochemically active, convert a number of carbohydrates into acid, and do not dilute gelatin.
Toxin formation. Streptococci produce a complex exotoxin, individual fractions of which have different effects on the body: hemotoxin (O- and S-streptolysins), leukocidin, lethal toxin, cytotoxins (damage liver and kidney cells), erythrogenic (scarlet fever) toxin. In addition to toxins, streptococci secrete a number of pathogenic enzymes that play an important role in the development of diseases - hyaluronidase, fibrinase, DNAse, proteinase, amylase, lipase, and the like. Streptococci are characterized by the presence of heat-stable endotoxins and allergens.
Antigens and classification. Streptococcal cells have an M-antigen (protein), which determines their virulent and immunogenic properties, a complex T-antigen (protein), C-antigen (polysaccharide) and P-antigen (nucleoprotein). Based on the presence of polysaccharide fractions, all streptococci are divided into 20 serological groups, which are reflected in capital letters Latin alphabet from A to V. Within individual groups, they are further divided into species, serovars, designated by numbers. Most streptococci that are pathogenic to humans are included in group A. In addition, a certain clinical significance have groups B, C, D, H, K.
The genus Streptococcus has many species. The most important of them are S. pyogenes, S. viridans, S. pneumoniae, S. faecalis, and anaerobic streptococci. Opportunistic species include representatives of the normal microflora of the oral cavity (S. salivarius, S. mitis, S. sanguis, etc.), as well as other human biotopes.
Ecology.Streptococci are less common in the external environment than staphylococci. Based on environmental characteristics, they are divided into several groups. One of them includes species that are pathogenic only for humans (S. pyogenes), the other - for animals and humans (S. faecalis), the third - opportunistic (S. salivarius, S. mitis). Streptococci of human ecovars, in addition to the oral cavity, are found on the mucous membranes of the upper respiratory tract and genital organs, on the skin, and in the intestines. The source of infection can be patients and carriers. Human diseases arise as a result of both exogenous and endogenous infection. The main mechanism of infection is airborne. In the occurrence and development of streptococcal infections, not only the immunodeficiency state is of great importance, but also the previous sensitization of the body to allergens.
The resistance of streptococci in the external environment is less than that of staphylococci. When dried, especially when surrounded by a protein shell, they persist for several days, but lose virulence. When heated to 70 °C they die within 1 hour, the most commonly used disinfectant solutions cause their death in 15-20 minutes.
Human diseases. Streptococci can cause the same variety of purulent-septic infections as staphylococci (boils, abscesses, cellulitis, panaritium, sepsis, osteomyelitis, etc.). But they can also cause other diseases that are not characteristic of staphylococci - scarlet fever, rheumatism, beshikha, and the like.
Penetrating into the blood of women during childbirth, they cause postpartum sepsis. Viridans streptococci cause endocarditis.
Anaerobic and fecal streptococci cause enterocolitis and take part in the development of dental caries. Penetrating into the tooth tissue, they destroy dentin and burden the process.
Immunity for streptococcal infections, except for scarlet fever, it is weak, unstable and short-lived. After suffering from diseases, different antibodies are formed, but protective value have only antitoxins and type-specific M-antibodies. On the other hand, people who have been ill often experience allergization of the body, which explains the tendency to relapse and recurrent illnesses.
Laboratory diagnostics.
The material for research is mucus from the oropharynx and nasopharynx, pus, wound contents, blood, sputum, and urine. It is inoculated onto sugar broth and blood agar. Bacteriological examination is carried out in the same way as for staphylococcal infections. Isolated pure cultures are identified by their morphological characteristics, the nature of hemolysis, biochemical activity, which makes it possible to identify individual species. Be sure to test sensitivity to antimicrobial drugs. Serological reactions are also carried out.
Prevention and treatment.
Streptococci, especially group A, as many years ago, are highly sensitive to penicillin and erythromycin. Some species are resistant to tetracyclines. Aminoglycosides enhance the bactericidal effect of penicillin. Sulfonamide drugs are also quite effective, but resistance to them easily arises. General methods prevention of streptococcal infections are basically the same as for staphylococcal infections. Specific methods of prevention and therapy have not yet been fully developed.
The role of streptococci in the etiology of scarlet fever and rheumatism . At the end of the last century, it was suggested that the causative agent of scarlet fever is hemolytic streptococcus. It was almost always sown from the tonsils of patients and from the blood of children who died of scarlet fever. In 1904 I.G. Savchenko obtained the exotoxin of the causative agent of this disease and produced an anti-scarlet fever serum. The Dick couple (1923) obtained a toxin (erythrogenin), which caused characteristic redness and rash and was produced only by streptococci isolated from scarlet fever.
Scarlet fever is highly contagious childhood disease with a sudden onset, tonsillitis, fever, and a characteristic small rash on the skin.
Infection occurs by airborne droplets. The source of infection is patients and bacteria carriers. In the first period of the disease, the toxin acts, in the second, streptococcus acts as the causative agent of many complications (otitis, neck phlegmon, nephritis, joint inflammation, sepsis). After an illness, antitoxic and antimicrobial immunity is developed. Possible cases of recurrent disease. The diagnosis of scarlet fever is made based on the clinical picture and epidemiological data. In doubtful cases, mucus from the oropharynx is cultured, streptococci are isolated and identified.
Treatment is carried out with antibiotics (penicillin, ampiox, gentamicin, cefamezin) and sulfonamide drugs. WITH for preventive purposes the patient is isolated. Those who have recovered from the disease are allowed into children's institutions and schools 12 days after recovery, and those who were in contact - 7 days after isolation. For prophylactic purposes, contact children are sometimes given immunoglobulin.
It is believed that S. pyogenes can also cause rheumatism, an acute febrile infectious-allergic disease with overwhelming damage to the heart and joints. In patients, streptococci are often isolated from the throat and blood, and in more late period find specific antibodies - antistreptolysins, antifibrinolysins, antihyaluronidase. In the occurrence and course of rheumatism, sensitization of the body by allergens is important, which can occur with any form of streptococcal infection. When treating rheumatism in all stages, penicillin, bicillin and other antibiotics are used.
Streptococcus pneumoniae (pneumococcus)
Streptococci pneumonia (under the old nomenclature - pneumococci) were first described by L. Pasteur in 1881. They were isolated in pure culture and their role in pneumonia was clarified by K. Frenkel and A. Weixelbaum (1886).
Morphology and physiology. Streptococcus pneumoniae is a pair of elongated lanceolate-shaped cocci that resemble the contours of a candle flame. Their sizes range from 0.5 to 1.5 microns. In the human body, they form a capsule that surrounds two cells together. When grown on nutrient media she is absent. They have no spores or flagella and are gram-positive.
Pneumococci are facultative anaerobes, but also grow well under aerobic conditions at 37 °C. They are not cultivated on simple media. They are grown on media supplemented with blood or serum. On blood agar, colonies form small transparent dewdrops surrounded by a greening zone.
In liquid media they cause slight turbidity with sediment. Biochemically active, they decompose a number of carbohydrates into acid, gelatin does not thin out. Virulent pneumococci decompose inulin and dissolve in bile, which is used for their identification. They produce hemotoxin, leukocidin, hyaluronidase, and also have endotoxin. The virulent properties of pneumococci are mainly determined by capsules that suppress phagocytosis.
Antigens and classification. Streptococcus pneumoniae has three main antigens - cell wall polysaccharide, capsular polysaccharide and M protein. Based on the capsular antigen, all pneumococci are divided into 85 serovars, 15 of which can cause lobar pneumonia, septicemia, meningitis, arthritis, otitis media, sinusitis, rhinitis, and creeping corneal ulcers in humans.
Ecology. The main biotopes of pneumococci in humans are the oropharynx and nasopharynx. From here they enter the lower respiratory tract and, with a decrease in the body's resistance and a weakened immune system, can cause pneumonia and other diseases. If the pathogen is excreted in sputum, exogenous infection of healthy people by airborne droplets is possible. Carriage of pneumococci and incidence are seasonal with maximum frequency in winter. Outside the body, streptococci pneumonia quickly die. They are highly sensitive to disinfectants. Heating to 60°C inactivates them after 10 minutes. Sensitive to penicillin and its derivatives.
Immunity
has a type-specific character, but is of low tension and short-lived. On the contrary, some people, after an illness, develop increased sensitivity to repeated infections or the disease becomes chronic.
Laboratory diagnostics. The material for research is sputum, blood, mucus from the oropharynx and nasopharynx, pus, cerebrospinal fluid, and the like. Primary bacterioscopy of the material and its inoculation on nutrient media yields little, since the oral cavity and other biotopes contain similar morphology, but non-pathogenic pneumococci. The main, most accurate, early and reliable method laboratory diagnostics is to perform a biological test on white mice, which are the most sensitive animals to pneumonia streptococci. After intraperitoneal infection, they develop sepsis; culture of blood from the heart makes it possible to quickly isolate a pure culture and identify it.
Prevention and treatment. General preventive measures boil down to keeping the body cool and avoiding severe hypothermia. Specific prevention not carried out, there are no vaccines. Penicillin, erythromycin, oleandomycin and sulfonamide drugs are successfully used for treatment.
The genus of streptococci also includes S. faecalis (fecal streptococcus, enterococcus), a spherical or oval-shaped diplococcus that inhabits the intestines of people and animals. The ability of enterococci to multiply in food products sometimes leads to foodborne illnesses. As an opportunistic microbe, when the body's defenses are weakened, it can cause purulent-septic diseases, more often in the form of a mixed infection. Most clinical strains of enterococci are highly resistant to antibiotics and other chemotherapeutic drugs.
Anaerobic streptococci (Peptostreptococcus anaerobius, P. lanceolatum, etc.). can also be causative agents of severe postpartum purulent-septic diseases, gangrenous processes and even sepsis.
Gram-negative cocci
Gram-negative cocas belong to the Neisseriaceae family. The family got the name in honor of A. Neiser, who was the first to discover in 1879 one of the species of this group - the causative agent of gonorrhea. The pathogen is also important in human infectious pathology meningococcal infection. Other species belong to opportunistic microorganisms, which are representatives of normal human microbiocenoses, but can sometimes cause hospital infections.
Meningococci (Neisseria meningitidis)
The causative agent of epidemic purulent cerebrospinal meningitis was first described and isolated in pure culture by A. Weixelbaum in 1887.
Morphology and physiology. Meningococcal cells have a bean-like shape or the appearance of coffee beans, are arranged like diplococci, do not form spores or flagella, and have delicate capsules in the body. The morphology is similar to gonococci. In cerebrospinal fluid smears, leukocytes are located predominantly inside. Meningococci have fimbriae, with the help of which they adhere to the cells of the mucous membrane of the upper respiratory tract.
Meningococci - aerobes and facultative anaerobes - are very fastidious in nutrient media to which blood or serum is added. Optimum cultivation is at 37 °C, preferably in an atmosphere of 5-8% CO2. On a solid medium they form delicate, transparent, colorless colonies of mucous consistency, on a liquid medium they form cloudiness and sediment at the bottom, and over time a film appears on the surface. The biochemical activity of meningococci is weak; they ferment only glucose and maltose to acid.
Neisseria meningitis does not produce a true exotoxin; their endotoxin is heat-resistant and highly toxic. The severity of the clinical course of meningococcal infection largely depends on it. The pathogenicity factor is the capsule, fimbriae, hyaluronidase, neuraminidase and outer membrane protein.
Antigens and classification. Based on the polysaccharide capsular antigen, meningococci are divided into 9 serological groups, which are designated by large with Latin letters(A, B, C, D, X, Y, Z W-135, E-29). Until recently, meningococci of groups A and B dominated in our country, and the former more often caused epidemic outbreaks of meningococcal infection. Other serological groups are now found.
Ecology.
The main biotope of meningococci in the body is the mucous membrane of the nasopharynx of patients and carriers. They are the source of meningococcal infection. Transmission occurs by airborne droplets in large crowds of people (barracks, educational institutions, kindergartens), where close and prolonged contacts are possible. Once in the external environment, meningococci quickly die. Known disinfectant solutions kill them in a few minutes. They are very sensitive to penicillin, erythromycin, tetracycline.
Human diseases.
Children aged 1-8 years are most often affected. The place of primary localization of the pathogen is the nasopharynx. From here, meningococci penetrate into the lymphatic vessels and blood. Either a local (nasopharyngitis) or a generalized form of infection develops (meningitis, meningococcemia, meningoencephalitis, endocarditis, arthritis, etc.).
With the massive breakdown of microbial cells, endotoxin is released and toxinemia occurs. Endotoxin shock may occur. Different clinical manifestations diseases depend both on the activity of the body's defenses and on the virulence of meningococci. In recent years, cases of severe meningococcemia have become more frequent. In the environment of the patient, bacteria carriage very often occurs among contact persons.
Immunity. Innate immunity is quite stable. The disease occurs in one out of 200 bacterial carriers. After the generalized form of meningococcal infection, persistent immunity develops. Repeated cases of the disease are rare. During the disease process, the body produces aglutinins, precipitins, and complement-fixing antibodies.
Laboratory diagnostics. To diagnose nasopharyngitis and identify bacterial carriage, mucus from the nasopharynx is examined, meningitis - cerebrospinal fluid, and if meningococcemia and other forms of generalized infection are suspected - blood. Samples containing material are protected from cooling and examined immediately. Smears are prepared from the sediment of cerebrospinal fluid and blood and stained with methylene blue. A pure culture of meningococci is isolated on serum media and the serogroup is determined. IN Lately immunological methods of express diagnostics have been introduced into laboratory practice from the detection of meningococcal antigen in the cerebrospinal fluid using immunofluorescence, enzyme-labeled antibody reactions, etc.
Prevention and treatment. General preventive measures come down to early diagnosis, hospitalization of patients, sanitization of bacteria carriers, quarantine in children's institutions. For the purpose of specific prevention during epidemic outbreaks of meningococcal infection, a chemical vaccine is used from polysaccharide antigens of serogroups A, B and C. Vaccination is carried out for children 1-7 years old. For treatment, penicillin, rifampicin, chloramphenicol and sulfa drugs, especially sulfamonomethoxine, are used.
Gonococci (Neisseria gonorrhoeae)
Morphology and physiology. Gonococcus, the causative agent of gonorrhea and blenorrhea, has a fairly characteristic morphology.
Bacterial cells are bean-shaped, arranged in pairs, concave sides inward and convex sides outward, gram-negative.
Their sizes are 0.7-1.8 microns. In smears from pus, they are located inside leukocytes, and in smears from pure cultures, gonococci are shaped like coffee beans. They do not form spores and are immobile, but have fimbriae with which they attach to the epithelial cells of the genitourinary tract. In chronic gonorrhea, as well as under the influence of drugs, gonococci change shape, size, and color, which must be taken into account when diagnosing the disease in a laboratory.
Neisseria gonorrhea is very fastidious about nutrient media. Under aerobic conditions they grow on freshly prepared media with native protein (blood, serum, ascitic fluid) with sufficient humidity, 3-10% CO2 in the atmosphere. Colonies are small, transparent, round, with smooth edges and a shiny surface. The broth forms a slight cloudiness and a film on the surface. Their enzymatic properties are weakly expressed; only glucose is broken down from carbohydrates; proteolytic enzymes are absent. Gonococci do not produce exotoxin, but have a heat-stable endotoxin that is toxic to humans and laboratory animals.
Antigenic structure gonococci is heterogeneous and variable. It is represented by protein and polysaccharide complexes. 16 serovars have been described, but their determination is not carried out in laboratories.
Ecology.
Only humans suffer from gonorrhea. The main biotopes of gonococci are the mucous membrane of the genital organs and the conjunctiva. They cannot exist outside the body, as they quickly die from drying out, cooling and temperatures above 40 °C. Very sensitive to solutions of silver nitrate, phenol, chlorhexidine and many antibiotics. However, due to a significant increase in diseases in recent years and improper treatment, the number of Neisseria resistant to antibiotics and sulfonamide drugs has increased.
Human diseases.
The source of gonococcal infection is only a sick person. The pathogen is transmitted sexually, less often through household items (towels, sponges, etc.). Once on the mucous membrane of the genitourinary organs, gonococci, thanks to the fimbriae, exhibit high adhesive properties, fixate on epithelial cells, multiply and penetrate the connective tissue. Purulent inflammation of the urethra and cervix occurs. In women, the tubes and ovaries are also affected, in men - prostate and seminal vesicles. Gonococci rarely cause generalized processes, but at times sepsis, inflammation of the joints, endocarditis, and meningitis may occur. With neonatal blenorrhea, purulent inflammation of the mucous membrane of the eyes occurs.
Immunity. There is no specific immunity to gonococci in humans. Past illness also does not leave stable and long-term immunity. The antibodies formed do not have protective properties. Cellular immunity is not formed, phagocytosis is incomplete: gonococci are not only preserved in leukocytes, but also multiply and can be transferred to other organs.
Laboratory diagnostics. The material being examined is discharge from the urethra, vagina, cervix, urine; with blenorrhea - pus from the conjunctiva of the eye. The main diagnostic method is microscopic. Smears are stained with Grammar methylene blue. Detection of bean-like diplococci inside leukocytes by microscopy makes it possible to diagnose gonorrhea. Isolation of pure culture and its identification are much less common. In the chronic course of the disease, the RZK or indirect hemagglutination reaction is used.
Prevention and treatment. Preventive measures consist of carrying out sanitary and educational work among the population, timely identification and treatment of patients. For individual prevention after casual sexual intercourse, use a 0.05% chlorhexidine solution. In order to prevent blenorrhea, all newborns are given a solution of penicillin or silver nitrate instilled into the eyes. Vaccine prophylaxis is not carried out. Gonorrhea is treated with penicillin and sulfa drugs. In chronic forms, killed gonococcal vaccine is used for therapeutic purposes.
Peptococci and peptostreptococci
Bacteria of the genera Peptococcus and Peptostreptococcus - gram-positive shaType-like anaerobes that do not form spores and do not have flagella. Individual viewsThey live in the intestines healthy people, they are also found in the oral cavity,in the nasopharynx, genitourinary tract. In inflammatory processes (appendicitis,pleurisy, brain abscesses) these microorganisms are isolated in association with othersmi bacteria as pathogens of mixed infections.
In laboratory diagnostics from pus, pieces of affected tissue, bloodisolate the culture and identify it.
Treatment is usually carried out with penicillin, carbecillin, levomycetin.
Veillonella
They multiply on milk agar, where they form a star-shaped brilliant, like diamonds, colonies with a diameter of 1-3 mm. Veillonella do not formoxidase and catalase, do not ferment carbohydrates, do not liquefy gelatin, do notchange milk, do not produce indole, but reduce nitrates. Kinds veillo nell distinguished by antigenic properties.
Pathological processes in which Veillonella are isolated (usuallyin association with other microorganisms), these are soft tissue abscesses, ranew infections, sepsis.
1. Laboratory diagnosis of staphylococcal and streptococcal infections
The material for research is pus, blood, sputum, mucus from the mouth, nasopharynx, inflammatory exudate, urine; in case of suspected foodborne illness - gastric lavage, vomit, feces, leftover food; during sanitary and bacteriological controls - washes from hands, tables and other objects.
From open purulent lesions, the material is taken with a cotton swab after removing the wound plaque, which contains saprophytic staphylococci from the air, skin, and the like. A puncture is made from closed abscesses with a sterile syringe. Mucus from the oropharynx and nasopharynx is taken with a sterile swab. Sputum and urine are collected in sterile tubes and jars. Blood (10 ml) taken from the ulnar vein, and cerebrospinal fluid - during puncture of the spinal canal, are aseptically sown near the patient's bed near 100 ml of sugar broth.
From all materials, except blood and swabs, smears are prepared, stained for Gram, microscopically examined, inoculated on blood and yolk-salt agar, and grown for 24 hours at 37 °C. Crops should be done immediately and on fresh media. After 24 hours, the colonies are examined, the presence of hemolysis, lecithinase, and pigment is noted; smears from colonies reveal typical gram-positive cocci. Subculture is done on slanted agar to isolate a pure culture, and after obtaining it, glucose fermentation under anaerobic conditions and virulence factors - plasmacoagulase, DNase, hyaluronidase, necrotoxin, etc. are determined. The sensitivity of the culture to antibiotics must be determined in order to rationally select drugs for treatment. To identify the source of infection using an international set of staphylococcal bacteriophages, a phagovar of the isolated culture is installed. In strains isolated from foodborne infections, the ability to produce enterotoxin is determined. To do this, the culture is sown on a special medium and incubated at 37 °C in an atmosphere of 20% CO2 for 3-4 days, filtered through membrane filters and injected into the abdominal cavity of suckling kittens or with a probe into the stomach.
For streptococcal infections, the same material is taken for laboratory diagnosis in a similar way as for diseases of staphylococcal etiology. In smears from the test material, streptococci are located in short chains, sometimes in the form of diplococci or single cells, so it is often impossible to distinguish them from staphylococci. Therefore, it is necessary to carry out bacteriological research. Since streptococci are fastidious in nutrient media, cultures are done on sugar broth and blood agar. After 24 hours in a liquid medium, growth is observed in the form of a sediment at the bottom of the test tube. Small, flat, dryish colonies with areas of hemolysis or greening grow on agar. In smears from colonies, streptococci are located alone, in pairs or in short chains, whereas in smears from broth culture they form typical long chains. IN next days isolate a pure culture, determine the species, serogroup and serovar.
Determination of the sensitivity of streptococci to antibiotics is carried out on AGV medium with the addition of 5-10% defibrinated rabbit blood.
To isolate anaerobic streptococci, cultures are carried out on Kitta-Tarozzi medium, where they grow with the formation of gas. The virulence of streptococci is determined by their ability to produce toxins and enzymes (hemolysin, hyaluronidase, fibrinase, etc.) or by infecting white mice.
In most cases, a bacteriological study is not carried out to diagnose scarlet fever, since the diagnosis of the disease is based on clinical symptoms.
Serological diagnosis of streptococcal infections is rarely carried out, mainly when the pathogen cannot be isolated. At the same time, antibodies against streptococcal toxins (antistreptolysin O, antistreptolysin S, antistreptohyaluronidase) are determined in the blood of patients. More often, such studies are carried out for chronic streptococcal infections, for example, for rheumatism.
In order to monitor the sanitary condition of enterprises Catering and personal hygiene of their employees, bacteriological examinations are carried out by inoculating swabs from hands, utensils, and equipment. The same swabs are made from the hands of surgeons, midwives, operating nurses, instruments, and the like to identify pyogenic cocci. In addition, at medical workers mucus from the nasopharynx is examined to determine the carriage of Staphylococcus aureus. For this purpose, the laboratory prepares sterile cotton swabs on wooden sticks or aluminum wire in test tubes with sugar broth. With such a swab soaked in the medium, wash out the hands (palms, back side, between the fingers, nail bed), and objects. The swab is lowered into a test tube, dipped into the broth, and placed in a thermostat at 37 °C. After 18-20 years, reseeding is done in order to isolate a pure culture and determine the species.
When diagnosing pneumococcal infections use bacterioscopic, bacteriological and biological methods. The material to be examined is sputum, pus, cerebrospinal fluid, blood, oro- and nasopharyngeal swabs. Streptococci pneumonia quickly die, so the test material must be delivered to the laboratory as soon as possible. Smears are prepared from the material (except blood), stained with Gram and Hins, and microscoped. Identification of lanceolate diplococci surrounded by a capsule allows us to assume the presence of pneumococci. But there may be saprophytic diplococci on the nasopharyngeal mucosa. Therefore, a bacteriological study is carried out. The material is sown on blood agar and whey broth, a pure culture is isolated and the species is determined. At the same time, a biological method is used. To do this, white mice are injected with material into the abdominal cavity. Animals die after 12-18 hours. Culture of blood from the heart at autopsy yields a pure culture of the pathogen. To differentiate it from other streptococci, the culture is sown in a bile broth, where pneumococci, unlike other species, are quickly lysed.
2. Laboratory diagnosis of diseases caused by Neisseria
To carry out bacteriological diagnosis of gonorrhea, microscopic, bacteriological and serological methods are used. For acute gonorrhea microscopic picture in smears is so characteristic that the diagnosis is made quickly enough. Material from the urethra is taken like this. The external opening of the urinary canal is wiped with a sterile swab soaked in an isotonic sodium chloride solution. Then, pressing lightly on the urethra, squeeze out a drop of pus. In women, a drop of discharge from the urethra or cervix is taken with a loop. Two smears are made, one of them is stained with methylene blue, the other with Gram. Many leukocytes are found in the smears; in the cytoplasm of some of them there are characteristic bean-shaped diplococci. When stained with methylene blue, the cytoplasm of leukocytes appears blue, gonococci and cell nuclei appear dark blue. According to Gram's method, Neisseria are colored red. Based on microscopy, a result about the identification of gonococci is quickly obtained.
In chronic gonorrhea, gonococci are often not found in smears. Then the pathogen is isolated and identified. Due to the high sensitivity of gonococci to temperature changes, material from the patient during transportation is protected from low temperatures (especially in winter) and quickly delivered to the laboratory. It is even better to sow the taken material near the patient’s bed with fresh, moist, heated serum agar or MPA made from rabbit meat. 10 U/ML of polymyxin and ristomycin are added to the media to suppress the growth of foreign microflora. Crops are grown in an atmosphere with 10% CO2. The isolated cultures are identified by biochemical characteristics (gonococcus decomposes only glucose).
In cases of chronic gonorrhea, a serological diagnostic method is also used - the Bordet-Gengou complement fixation reaction. Blood serum (antibodies) is taken from the patient. The antigen for RSK is a gonococcal vaccine or a special antigen made from gonococci killed by antiformin. RNGA and intradermal allergy test are also used. Jr medical staff must strictly maintain medical confidentiality regarding the diagnosis of a sexually transmitted disease, so as not to cause moral harm to the patient.
For laboratory diagnosis of meningococcal infections, the materials used are mucus from the nasopharynx, cerebrospinal fluid, blood, and scrapers from the veins on the skin. Discharge from the posterior wall of the nasopharynx is taken on an empty stomach with a cotton swab attached to a bent wire. The end of the tampon is directed upward and inserted behind the soft palate, while the root of the tongue is pressed with a spatula. During collection, the material taken should not touch the teeth, tongue and mucous membrane of the cheeks. It is immediately inoculated on serum agar with the addition of ristomycin to inhibit the growth of gram-positive cocci.
Cerebrospinal fluid taken during lumbar puncture into a sterile tube and immediately inoculated on serum medium or, protected from cold, quickly delivered to the laboratory. Blood in an amount of 10 ml is obtained from a vein before the start of treatment and sown near the patient’s bed in a bottle with a liquid medium, grown in an atmosphere of 5-10% CO2. Meningococci in the cerebrospinal fluid can be quickly detected microscopically. If the fluid is purulent, smears are prepared without any previous treatment; if there is slight turbidity, centrifuge and smears are made from the sediment. It is better to stain with methylene blue, while meningococci have the appearance of bean-like diplococci located in leukocytes and their position. In meningococcemia, Neisseria can be detected in thick drops of blood. The results of microscopy are immediately reported to the doctor.
Simultaneously with bacterioscopy, bacteriological examination is also carried out. A day after the initial inoculation, the growth pattern in the vial or isolated colonies on a solid medium is noted, subcultured onto a slanted serum agar to isolate pure cultures, which are then identified by the oxidase reaction and other biochemical characteristics and the serogroup is determined.
Recently, rapid diagnostic methods have become important, which make it possible to detect Neisseria antigens using enzyme-linked immunosorbent assay (ELISA), immunofluorescence and immunoelectrophoresis. In the presence of meningococcal erythrocyte diagnosticum serogroups A, B and C, an indirect hemagglutination test can be performed to detect antibodies in the blood serum of patients.
Delivery of the material to the laboratory is accompanied by a direction in which the surname and initials of the patient (carrier), diagnosis of the disease, type of material, what studies need to be carried out, date and time of collection of the material are noted. After conducting research, the bacteriological laboratory issues a response in the form of a “Result of microbiological analysis,” which indicates that S. aureus (S. pyogenes, S. pneumoniae) was isolated from patient A. from the blood (pus, urine, sputum, etc.), which is sensitive (resistant) to antibiotics (listed).
Information sources:
ENTEROBACTERIA
Family Enterobacteriaceae includes a large group of opportunistic and pathogenic bacilli for humans, the habitat of most of which is the intestines of humans and animals. This family includes 14 genera. Diseases
in humans, it is most often caused by representatives of the genera Escherichia, Shigella, Salmonella, Klebsiella, Proteus, Yersinia . Other enterobacteria are either rarely found in human pathology or are completely non-pathogenic.
Morphology, physiology.Enterobacteriaceae are short rods from 1 to 5 microns in length, 0.4-0.8 microns wide (see Fig. 3.1). Some species are mobile - peritrichous, while others lack organs of movement. Many have fimbriae (piles) different types, fibrils that perform an adhesive function, and sex pili involved in conjugation.
Enterobacteriaceae grow well on simple nutrient media and produce saccharolytic, proteolytic and other enzymes, the definition of which is of taxonomic importance. In table Table 20.2 presents the most important biochemical characteristics of some genera and species of Enterobacteriaceae. Within some species, fermentovars are isolated.
A number of enterobacteria produce bacteriocins (colicins), information about the synthesis of which is encoded in CO1 plasmids. Colicinotyping and colicinogenotyping of enterobacteria as methods of intraspecific strain marking are used for epidemiological purposes (to establish the source and routes of transmission of the causative agent of intestinal infections).
Colonies of E. coli on MPA
Colonies of E. coli on Endo medium
Antigens. Enterobacteriaceae have O-(somatic), K-(capsular) and H-(flagellate in motile bacteria) antigens. O-antigens, like those of all gram-negative bacteria, are lipopolysaccharides (LPS) of the cell wall. Their specificity is determined by terminal (determinant) sugars - hexoses and amino sugars, covalently linked to the base part of LPS. K-antigens are also contained in the LPS of the cell wall, but are located superficially and thereby mask the O-antigen.
Antigens are localized in fimbriae and fibrils. Antibodies to them prevent the adhesion of bacteria to cellular receptors.
Ecology and distribution.Opportunistic enterobacteria live in the intestines of vertebrates and humans, including (for example, E. coli )in the composition of the biocenosis of the large intestine.
Pathogenicity Enterobacteriaceae is determined by virulence and toxicity factors inherent in various combinations to individual species that cause infectious diseases in humans. All enterobacteria contain endotoxin, which is released after the destruction of microbial cells. Adhesion on the receptors of sensitive cells is ensured by fimbriae and fibrillar adhesins, which have specificity, i.e. the ability to attach to cells of certain tissues in the macroorganism, which is due to the affinity of the corresponding adhesins to the structures that perform the functions of receptors. Colonization of tissue is accompanied by the production of enterotoxins by some enterobacteria, and by others, cytotoxins. Shigella, for example, penetrates epithelial cells, where they multiply and destroy cells - a local pathological focus appears. Salmonella, phagocytosed by macrophages, do not die in them, but multiply, which leads to the generalization of the pathological process.
Escherichia
Genus Escherichia named after T. Escherich, who in 1885 first isolated bacteria from human feces and described in detail the bacteria now called Escherichia coli - Escherichia coli.
Species E. coli includes opportunistic coli, which are permanent inhabitants of the intestines of humans, mammals, birds, fish, reptiles, as well as variants pathogenic for humans, differing from each other in antigenic structure, pathogenetic and clinical features the diseases they cause.
Morphology, physiology. Escherichia are rods measuring 1.1 - 1.5 X 2.0-6.0 microns. They are arranged randomly in preparations. The motile ones are peritrichous, but there are also variants lacking flagella. All Escherichia have fimbriae (pili).
Reproducing at a temperature of 37 ° C, on dense media they form S- and R -colony. In liquid media they produce turbidity, then a sediment. Many strains have a capsule or microcapsule and form mucous colonies on nutrient media.
E. coli produce enzymes that break down carbohydrates, proteins and other compounds. Biochemical properties are determined when differentiating Escherichia from representatives of other genera of the Enterobacteriaceae family.
Antigens. In the complex antigenic structure of E. coli, the main one is the O-antigen, the specificity of which forms the basis for the division of Escherichia into serogroups (about 170 O-serogroups are known). Many strains of individual serogroups have common antigens with microorganisms of other serogroups of Escherichia, as well as with Shigella, Salmonella and other enterobacteria.
K-antigens in Escherichia consist of 3 antigens - A, B, L , differing in sensitivity to temperature effects: B and L -antigens are thermolabile and are destroyed by boiling; A-antigen is thermostable and is inactivated only at 120 °C. The superficial location of K-antigens in the microbial cell masks the O-antigen, which is determined after boiling the test culture. In Escherichia, about 97 serovars of K-antigens are known.
H-antigens of Escherichia coli are type-specific, characterizing a specific serovar within O-groups. More than 50 different H-antigens have been described.
The antigenic structure of an individual Escherichia strain is characterized by a formula that includes the alphanumeric designations of O-antigen, K-antigen and H-antigen. For example. coli 0.26:K60 (B6): H2 or E. coli O111:K58:H2.
Ecology and distribution. Living in the intestines of humans and animals, E. coli are constantly excreted into the environment through feces. In water and soil they remain viable for several months, but quickly, within a few minutes, die from the action of disinfectants (5% phenol solution, 3% chloramine solution). When heated to 55 °C, the death of microorganisms occurs after 1 hour; at 60 °C they die after 15 minutes.
E. coli like opportunistic bacteria capable of causing purulent-inflammatory processes of various localizations. As endogenous infections, pyelitis, cystitis, cholecystitis, etc., called colibacteriosis, occur. With severe immunodeficiency, there may be coli-sepsis. Wound suppuration also develops as an exogenous infection, often in association with other microorganisms.
Unlike opportunistic pathogens, pathogenic Escherichia cause various forms of acute intestinal diseases
Clinical manifestations of colienteritis
Biochemical properties mostly typical for the genus Salmonella Distinctive features are: the absence of gas formation during fermentation of S. Typhi, the inability of S. Paratyphi A to produce hydrogen sulfide and decarboxylate lysine.
Epidemiology.Typhoid fever and paratyphoid fever are anthroponoses, i.e. cause disease only in humans. The source of infection is the patient or the bacteria carrier, who release the pathogen into the external environment with feces, urine, and saliva. The causative agents of these infections, like other salmonellae, are stable in the external environment and persist in soil and water. S. Typhi can become uncultivable. A favorable environment for their reproduction is food products (milk, sour cream, cottage cheese, minced meat, jelly). The pathogen is transmitted by water, which currently plays a significant role, as well as by nutritional and household contact routes. The infecting dose is approximately 1000 cells. The natural susceptibility of people to these infections is high.
Pathogenesis and clinical picture. Once in small intestine, typhus and paratyphoid pathogens invade the mucous membrane when
with the help of effector proteins TTSS-1, forming the primary focus of infection in Peyer's patches. It should be noted that in the submucosa the osmotic pressure is lower compared to the intestinal lumen. This promotes intensive synthesis of Vi-antigen, which increases the antiphagocytic activity of the pathogen and suppresses the release of proinflammatory tissue mediators by submucosal cells. The consequence of this is the lack of development of inflammatory diarrhea in the initial stages of infection and the intensive proliferation of microbes in macrophages, leading to inflammation of Peyer's patches and the development of lymphadenitis, resulting in a violation of the barrier function of the mesenteric lymph nodes and the penetration of salmonella into the blood, resulting in the development of bacteremia. This coincides with the end of the incubation period, which lasts 10-14 days. During bacteremia, which accompanies the entire febrile period, pathogens of typhoid and paratyphoid fever spread throughout the body through the bloodstream, settling in the reticuloendothelial elements parenchymal organs: liver, spleen, lungs, and also in the bone marrow, where they multiply in macrophages. From the Kupffer cells of the liver, salmonella enter the gallbladder through the bile ducts, into which they diffuse, into the gallbladder, where they also multiply. Accumulating in gallbladder, Salmonella causes inflammation and reinfects the small intestine with a flow of bile. The repeated introduction of Salmonella into Peyer's patches leads to the development of hyperergic inflammation in them according to the Arthus phenomenon type, their necrosis and ulceration, which can lead to intestinal bleeding and perforation of the intestinal wall. The ability of typhoid and paratyphoid pathogens to persist and multiply in phagocytic cells when the latter are functionally insufficient leads to the formation of bacterial carriage. Salmonella can also persist for a long time in the gallbladder, excreted in feces for a long time, and contaminate the environment. By the end of the 2nd week of the disease, the pathogen begins to be excreted from the body in urine, sweat, and breast milk. Diarrhea begins at the end of the 2nd or beginning of the 3rd week of the disease, from which time the pathogens are cultured from the feces.
Without a doubt, bacteria are the most ancient creatures on Earth. They are involved at every stage of the cycle of substances in nature. Over the billions of years of their life, bacteria have taken control of processes such as fermentation, rotting, mineralization, digestion, and so on. small ones, invisible to the eye fighters are everywhere. They live on various objects, on our skin and even inside our body. It may take more than one lifetime to fully understand their diversity. Still, let’s try to consider the main forms of bacteria, paying attention to Special attention spherical unicellular organisms.
The kingdom of bacteria, or what microbiology studies
Wildlife is divided into 5 main kingdoms. One of them is the kingdom of bacteria. It combines two subkingdoms: bacteria and blue-green algae. Scientists often call these organisms crushed, which reflects the process of reproduction of these single-celled organisms, reduced to “crushing,” that is, division.
Microbiology studies the kingdom of bacteria. Scientists in this field systematize living organisms into kingdoms, analyze morphology, study biochemistry, physiology, the course of evolution and their role in the planet’s ecosystem.
General structure of bacterial cells
All main forms of bacteria have a special structure. They lack a nucleus surrounded by a membrane capable of separating it from the cytoplasm. Such organisms are usually called prokaryotes. Many bacteria are surrounded by a mucous capsule, which causes resistance to phagocytosis. A unique feature of the representatives of the kingdom is the ability to reproduce every 20-30 minutes.
Meningococcus is a paired bacterium that looks like buns stuck together at the base. By appearance somewhat reminiscent of gonococcus. The area of action of meningococci is the mucous membrane of the brain. Patients with suspected meningitis must be hospitalized.
Staphylococci and streptococci: characteristics of bacteria
Let's consider two more bacteria, the spherical shapes of which are linked into chains or develop in spontaneous directions. These are streptococci and staphylococci.
There are many streptococci in the human microflora. When these spherical bacteria divide, they create beads or chains of microorganisms. Streptococci can cause infectious and inflammatory processes. Favorite localization locations - oral cavity, gastrointestinal tract, genitals and respiratory mucosa.
Staphylococci are divided in many planes. They create bunches of grapes from bacterial cells. They can cause inflammatory processes in any tissues and organs.
What conclusions should humanity draw?
Man is too accustomed to being the king of nature. More often than not, he only bows to brute force. But there is a whole kingdom on the planet in which organisms invisible to the eye are united. They have the highest adaptability to the environment and influence everything biochemical processes. Smart people have long understood that “small” does not mean “useless” or “safe.” Without bacteria, life on Earth would simply stop. And without careful attention to pathogenic bacteria, it will lose quality and gradually die out.
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