Microbiology: lecture notes Tkachenko Ksenia Viktorovna

2. Streptococci

2. Streptococci

They belong to the family Streptococcaceae, genus Streptococcus.

These are gram-positive cocci, arranged in chains or in pairs in smears. They are facultative anaerobes. Do not grow on nutrient media. On blood agar, small-dotted, pigmentless colonies are produced, surrounded by a zone of hemolysis: a - green, b - transparent. The disease is often caused by b-hemolytic streptococcus. In sugar broth, near-wall growth is given, and the broth itself remains transparent. Grow at 37°C. Streptococci are able to break down amino acids, proteins, carbohydrates. According to biochemical properties, 21 species are distinguished. Most of them are conditionally pathogenic.

The most important in the development of infectious diseases are:

1) S. pyogenus, the causative agent of a specific streptococcal infection;

2) S. pneumonia, the causative agent of pneumonia, can cause a creeping corneal ulcer, otitis, sepsis;

3) S. agalactia, may be part of the normal microflora of the vagina; infection of newborns leads to the development of sepsis and meningitis in them;

4) S. salivarius, S. mutans, S. mitis, are part of the normal microflora of the oral cavity; in oral dysbiosis are the leading factors in the development of caries.

streptococcal antigens.

1. Extracellular - proteins and exoenzymes. These are variant-specific antigens.

2. Cellular:

1) surface proteins are represented by surface proteins of the cell wall, and in S. pneumonia, by capsule proteins. They are variant-specific;

2) deep - teichoic acids, peptidoglycan components, polysaccharides. They are group specific.

pathogenicity factors.

1. Complexes of teichoic acids with surface proteins (play the role of adhesins).

2. M-protein (possesses antiphagocytic activity). This is a superantigen, that is, it causes polyclonal activation of immune system cells.

3. OF-protein - an enzyme that causes hydrolysis of blood serum lipoproteins, reducing its bactericidal properties. The OF protein is important for adhesion. According to the presence or absence of this protein, there are:

1) OF+ strains (rheumatogenic); the entrance gate is the pharynx;

2) OF-strains (nephritogenic); primary adhesion to the skin.

4. Enzymes of aggression and defense:

1) hyaluronidase;

2) streptokinase;

3) streptodornasis;

4) proteases;

5) peptidases.

5. Exotoxins:

1) hemolysins:

a) O-streptolysin (has a cardiotoxic effect, a strong immunogen);

b) S-streptolysin (weak immunogen, does not have a cardiotoxic effect);

2) erythrogenin (has a pyrogenic effect, causes capillary paresis, thrombocytolysis, is an allergen, occurs in strains that cause complicated forms of infection, in pathogens of scarlet fever, erysipelas).

1) etiotropic antibiotic therapy;

Diseases caused by streptococci have attracted the attention of doctors, microbiologists, scientists of other specialties for quite a long time. There is nothing surprising in this - dangerous strains of these types of bacteria can cause severe inflammatory reactions, and infection in some cases leads to death. In order for the fight against diseases to be more successful, it is necessary to study the pathogen in detail, evaluate the characteristics of its vital activity and identify what is effective against it at the present time, which drugs will not provoke the development of resistance in pathological forms.

general information

In microbiology, streptococci are commonly referred to as such life forms, the diameter of which varies between 0.8-1 microns. They are spherical or oval in shape. Bacteria are immobile and form chains whose length varies greatly. Based on the analysis of staining, streptococci are classified as gram-positive bacteria. Some species form a capsule. The chain size is regulated by external factors. The more nutritious the liquid medium, the longer the formation will be, while in the dense structure the chains are short, bundles appear.

Studying the growth of streptococci, scientists have found that shortly before dividing, the bacteria become ovoid. The process of reproduction relative to the plane of the chain is perpendicular. One bacterium separates into a pair.

Cultural qualities

If a life form is grown on agar containing blood elements, translucent rods are generated, the diameter of which does not exceed a couple of millimeters. Studies aimed at identifying the features of the activity of streptococci in the body made it possible to establish: on agar with blood inclusions, colonies of bacteria have no color or are colored grayish, they are easily removed with a loop. Hemolysis for varieties in terms of zone dimensions differs quite significantly - in some, the diameter is slightly larger than the size of the colony, in others it exceeds quite significantly.

Category A in microbiology, streptococci are capable of generating a greenish or brownish greenish hemolytic zone. The zone can be transparent, sometimes cloudy, and the intensity of staining and dimensions vary. The colony can also turn green. If the nutrient medium is liquid, more often the colony grows at the bottom, gradually rising along the walls. If you shake the substance, a suspension appears in the liquid in the form of flakes, grains. As a rule, to study the development of streptococci, agar is used, to which blood cells obtained from sheep and rabbits are added. Serum can be added. Agar is used semi-liquid or meat-peptone.

Nuances of breeding

Experiments organized in microbiology with streptococci have shown that a combined broth medium allows for good colony growth, accompanied by active production of toxins. The most effective use of casein hydrolyzate, yeast extract. Hemolytic life forms process glucose molecules, thus generating various acids, including lactic. It is this factor that limits the reproduction of the colony in the substrate.

Belonging to class A in microbiology, streptococci are able to remain viable for a long time, being dried, therefore they are found in dust, on objects. Virulence such cultures lose. Life forms belonging to this class show a pronounced sensitivity to the penicillin series - medicines belonging to it give a bactericidal effect. Bacteriostatic observed with the use of sulfanilamide.

History and observations

Streptococci were first identified in 1874 while studying erysipelas. The author of the research was the biologist Billroth. After some time, streptococcus pyogenes attracted the attention of the scientist Pasteur, who dealt with cases of blood poisoning, diseases associated with foci of suppuration. Streptococci are a numerous genus of bacteria. In its composition there are various forms of life, differing from each other physiologically, biochemistry, ecological features, the level of danger for human onanism.

All varieties of streptococci (including streptococcus agalactiae) belong to the category of chemoorganotrophic microorganisms that are demanding on the substrate for growth. Reproduction in the blood or a medium rich in sugar is possible. Certain varieties, when grown on blood agar, do not change it, which is why they were called non-hemolytic. Further studies of hemolyticity showed a significant variability of species, which limits the use of this feature for diagnostic purposes.

Important Features

To separate streptococci into groups, the difference in the process of carbohydrate fermentation is analyzed. True, this sign is not stable and clear enough to be applicable in the diagnosis of diseases provoked by the pathogen. Currently, the features of carbohydrate fermentation of streptococci are still being studied, and this feature is not used to identify varieties. Microorganisms belong to the aerobic class, they cannot generate catalase, which is how they differ from staphylococci.

The study of streptococcus agalactiae and other varieties revealed several antigens. Given the characteristics of antigens for a particular form of life, they make an accurate diagnosis - this helps to differentiate types. In 1933, Landsfield developed a system of differentiation into 17 serogroups. The division base is polysaccharide antigens. For their designation, it was decided to use Latin letters in accordance with the alphabet.

Form specifics

The most widespread variety is the group A streptococcus pyogenes. To divide within this group of its representatives into subspecies, analyze the M-antigen. Scientists know more than a hundred serotypes of A-serovar. It has been established that some types belonging to this class have cross-reacting antigenic structures, and their antibodies are able to react with kidney tissues, myocardium and other elements of the human body. Such antigens are able to provoke an immunopathological condition.

Growth and conditions

Studying the properties of streptococci, the features of their distribution, microbiologists have established: in nature, these bacteria are found abundantly, in a variety of environments. The division into several categories is accepted based on the ecological nuances of existence. Forms belonging to group A are dangerous only for humans, the second group includes not only pathogenic, but also conditionally dangerous forms that can affect both humans and animals. The third class is oral conditionally dangerous varieties. Some bacteria can cause anthroponotic infection, other species - anthropozoonotic.

In the human body, streptococci can be detected in the oral cavity, on the skin, in the intestinal tract, and in the upper organs of the respiratory system. Infection usually occurs through contact with a carrier of the pathogen, with a sick person, or through interaction with convalescents. Spread more often occurs by airborne droplets, somewhat less often through direct contact. In the outside world, a bacterium can survive for several days, but heating to 50 degrees leads to the death of microflora within half an hour, sometimes faster.

Status Refinement

Investigating cases of infection with pyogenic streptococci, microbiologists have proposed several effective options for making an accurate diagnosis. For research, samples of organic fluids are obtained from a sick individual. Use urine, purulent discharge, mucous membranes obtained from the nasal cavity, pharynx. The tissues are sent for bacterioscopic analysis, smears are prepared, stained in accordance with Gram's theory. Seeding involves the use of a Petri dish. In the laboratory, they resort to agar with blood inclusions.

As the colony grows, it is analyzed whether beta-hemolytic streptococcus occurs, or other features of hemolysis are observed. Then the isolated culture is finally identified based on the characteristics of the antigen and the specifics of the nuances. For its implementation, the precipitinogen is obtained from the culture used in the study. In addition, antisera to different serotypes are used for the test. If blood poisoning is expected, it is necessary to obtain this fluid from the patient's body for culture.

Nuances of analyzes

A special rapid test for streptococci is indicated if rheumatism is suspected. The analysis is carried out serological. The task of the doctor is to determine the presence of O-streptolysin antibodies, as well as to assess the features of precipitation, to identify C-reactive protein structures. The most relevant research practiced recently is PCR reactions.

What to do?

Currently, there are no measures to prevent infection with beta-hemolytic streptococci or other varieties of this type of bacteria. The developed vaccines and toxoids have shown their inefficiency, which makes specific prophylaxis at the level of modern technologies impossible. An anti-caries vaccine is at the stage of active development.

The therapeutic course involves the use of antibacterial compounds. Streptococci are able to develop resistance to various drugs, including the penicillin series, but this feature is acquired rather slowly. Beta-lactam antibiotics against streptococci are widely used. Benzylpenicillin is actively used. The cephalosporin preparations belonging to the first and second generation show a pronounced effect. You can use macrolides, aminoglycosides.

Diseases and their absence

Streptococci are quite widespread - they can be found on the flora, in the ground, on the skin of fauna. Intestinal streptococcus is known and common. It is far from always that bacteria of this genus cause serious diseases, and the infections themselves, if they occur, differ significantly in manifestations. The carriage of streptococci in the modern world is extremely widespread, while the carrier is healthy, but can transmit the bacterium to a susceptible individual. For the first time, streptococci were established, revealing the cause of cow mastitis. Currently, attention to this group of microorganisms is drawn due to the frequency of occurrence in human genitourinary infections. It was possible to establish the presence of varieties of streptococci in the male urethra, female birth canal. In regular sexual partners, the simultaneous carriage of bacteria is usually detected. It is customary to talk about carriage urethral, ​​pharyngeal. The first involves the presence of bacteria in the urethra, the second - in the oral cavity.

Among other bacterial diseases in the temperate zone, those provoked by streptococcus occupy one of the first places in terms of frequency of occurrence. Hemolytic varieties of these life forms cause disease not only in humans, but also in a variety of mammals. In healthy people, in the gastrointestinal tract, the reproductive system, streptococci are present on average in 5-40% of people. Class B is detected in almost every third healthy woman in the vagina. This is one of the two main reasons (along with nosocomial infection) that explains the prevalence of streptococcal infections among newborns. Infection usually occurs at the time of birth, infection with bacteria occurs in approximately 75% of cases among children whose mothers were carriers of the microflora.

Prevalence Features

As can be seen from the studies, most of the carriers of streptococci among people do not even suggest infection. This is due to the absence of symptoms. The bacteria are transmitted through intimate contact. Symptoms that may accompany infection often do not have specific features, similar to infection with chlamydia, mycoplasma and other pathogenic microorganisms that spread in a similar way. The patient notes dysuria, possible discharge with the inclusion of blood, pus, serous, inflammatory foci appear on the mucous membranes.

Streptococci as the cause of inflammatory processes have been actively considered since 1874, when they were identified in pus during a wound process complicated by infection. In 1906, scientists from different countries proved the importance of streptococcus in the pathogenesis of scarlet fever. Further study of the microflora made it possible to understand: streptococcus can initiate rheumatism, however, viruses are also probably involved in the process. Throat diseases associated with infection with streptococcus are extremely widespread. By the time the compulsory educational stage is completed, almost every child suffers from tonsillitis or tonsillitis several times due to infection, and the disease can flow almost without manifesting itself, while others have very severe cases. They indicate diseases of the throat caused by streptococci, hyperemia of the tonsils, swelling of the tissues of the throat and pain when swallowing, trying to speak.

Infection and consequences

Revealed: streptococcal infection of the throat in some cases leads to the development of rheumatism. On average, a complication occurs a couple of weeks after the underlying disease. The first rheumatic attack is characterized by fever, swelling of the joints, pain in this area. In the future, there is a risk of chronic heart disease, in which the integrity and functionality of the body's valves are impaired. Doctors have not yet been able to establish all the features of the formation of rheumatism. The following assumption is of interest: in the patient's body, an allergic response occurs to a certain compound generated by streptococci during their vital activity.

If angina is provoked by a rare hemolytic streptococcus, there is a risk of nephritis as a complication of the underlying disease. The inflammatory focus is localized in the kidneys, the ability of the organ to work is impaired. Hemolytic streptococcal forms can cause erysipelas. Bacteria penetrate through the integument, the integrity of which is broken, and then are able to seep into various internal structures and organs. There is a risk of a generalized process, that is, sepsis. Previously, the disease provoked a huge number of deaths, today it is considered curable if a therapeutic course with antibiotics is started on time. The likelihood of a fatal outcome is still there, but the frequency of occurrence of such cases has decreased significantly.

Infection: the nuances of the process

Streptococcal infection is accompanied by the destruction of red blood cells. In addition to those listed above, this class includes abscesses, phlegmon, boils. Osteomyelitis, endocarditis have a similar nature. Against the background of infection with streptococci, glomerulonephritis may develop. Pneumococcus is considered close in its characteristics to beta-hemolytic streptococcus, which provokes these diseases. This form of streptococcus is highly likely to cause pulmonary inflammation, sinusitis.

The activity of streptococcus is due to the ability of the microorganism to generate dangerous compounds. Streptolysin, produced by bacteria, negatively affects heart and blood cells. Another poison is erythrogenin, under the influence of which small blood vessels expand, areas of rashes are formed. The destruction of leukocytes is explained by the presence of leukocidin. Certain enzymes generated by the colony make it easier for it to spread throughout the body and penetrate various tissues.

Infection: noticeable immediately

The area of ​​penetration of streptococcus into the human body manifests itself as an inflammatory reaction. A focus with suppuration, a necrotic zone or a serous reaction is formed here. Bacteria generate specific enzymes that allow them to overcome the barrier defense system of the body and seep into the flow of lymph and blood. This leads to the appearance of inflammatory foci at a distance from the primary area of ​​implementation.

Poisons produced by the colony cause fever. The patient vomits, his head hurts and feels dizzy, there are problems with consciousness, especially pronounced with erysipelas, blood poisoning, scarlet fever. The infection is accompanied by an allergic syndrome associated with a response to components of bacterial cells. The immune system, trying to fight the invasion, harms the patient's body. After recovery, although there is immunity, it is not stable, short-lived, which explains the repeated incidence. The exception is the inability to re-sick with scarlet fever.

No. 8 Streptococcus. Taxonomy. Characteristic. Microbiological diagnosis of streptococcal infections. Treatment.
Taxonomy. Streptococci belong to the Firmicutes division of the Streptococcus genus. The genus consists of more than 20 species, among which there are representatives of the normal microflora of the human body and pathogens of severe infectious epidemic human diseases.
Morphological and cultural properties. Streptococci are small spherical cells arranged in chains, gram-positive, do not form spores, immobile. Most strains form a capsule consisting of hyaluronic acid. The cell wall contains proteins (M-, T- and R-antigens), carbohydrates (group-specific) and peptidoglycans. Easily transform into L-shapes. Pathogens grow on media enriched with carbohydrates, blood, serum, ascitic fluid. On dense media, they usually form small gray colonies. Capsular strains of group A streptococci form mucous colonies. On liquid media, streptococci usually grow near the bottom. Streptococci are facultative anaerobes. According to the nature of growth on blood agar, they are divided into cultural variants: a-hemolytic (green), b-hemolytic (complete hemolysis) and non-hemolytic.
resistance. Sensitive to physical and chemical environmental factors, they can remain viable for a long time at low temperatures. Antibiotic resistance develops slowly.
Pathogenicity. Based on the polysaccharide antigen, they are divided into serogroups (A, B, C ... O). Group A streptococci produce more than 20 substances that are antigenic and aggressive. On the surface of the cell there is a protein antigen M, which is closely associated with virulence (prevents phagocytosis). This protein determines the type of streptococci. Pathogenicity factors include streptokinase (fibrinolysin), DNase, hyaluronidase, erythrogenin. The most pathogenic for humans are group A hemolytic streptococci, called S. pyogenes. This species causes many diseases in humans: scarlet fever, erysipelas, tonsillitis, acute endocarditis, postpartum sepsis, chronic tonsillitis, rheumatism.
Immunity: post-infection unstable, not stressed.
Microbiological diagnostics. Material for research - pus, urine, blood, sputum.
Bacterioscopic method: Gram stain of smears from pathological material. With a positive result, chains of gram "+" cocci are found.
Bacteriological method: The test material is seeded on blood agar in a Petri dish. After incubation at 37 °C for 24 hours, the nature of the colonies and the presence of hemolysis zones around them are noted. From a part of the material taken from the colonies, a smear is prepared, stained according to Gram and microscoped. To obtain a pure culture, 1-3 suspicious colonies are subcultured into test tubes with slant blood agar and sugar broth. On blood agar, Streptococcus pyogenes forms small, hazy round colonies. In the broth, streptococcus gives a near-wall growth in the form of flakes, leaving the medium transparent. According to the nature of hemolysis on blood agar, streptococci are divided into three groups: 1) non-hemolytic; 2) a-hemolytic; 3) ?-hemolytic, forming a completely transparent zone of hemolysis around the colony. The final stage of bacteriological research is the identification of the isolated culture by antigenic properties. On this basis, all streptococci are divided into serological groups (A, B, C, D, etc.). The serogroup is determined in a precipitation reaction with polysaccharide precipitinogen C. Serovar is determined in an agglutination reaction. The identified culture of streptococcus is tested for sensitivity to antibiotics using the disk method.
Serodiagnostics: establish the presence of specific antigens in the patient's blood using RSK or precipitation reaction. Antibodies to O-streptolysin are determined to confirm the diagnosis of rheumatism.
Treatment: Broad-spectrum antibiotics (penicillins resistant to β-lactamase). With the isolation of streptococcus A - penicillin. Chemotherapy with antibiotics, to which the sensitivity of the microbe is revealed - levomycetin, rifampicin.
Prevention: specific - no. Nonspecific - identification, treatment of patients; conducting a routine examination of medical staff, vaccination streptococcal bacteriophage (liquid) - Streptococcus phagolysate filtrate. Applied externally, intradermally, intramuscularly ., O-streptolysin dry (lyophilized filtrate of the broth culture of streptococcus - an active producer of O-streptolysin. It is used for setting serological reactions - determining anti-O-streptolysin in the blood serum of patients).

The content of the article

streptococci

Discovered by T. Billroth in 1874 with erysipelas and a few years later by L. Pasteur with purulent diseases and sepsis. The genus Streptococcus includes numerous species that differ from each other in ecological, physiological and biochemical characteristics, as well as pathogenicity for humans.

Morphology, physiology

Cells are spherical or oval in shape, arranged in pairs or in the form of chains of different lengths. Gram-positive. Chemoorganotrophs. Demanding on the nutrient substrate. They reproduce on blood or sugar media. On the surface of solid media they form small colonies, on liquid media they give near-bottom growth, leaving the medium transparent. According to the nature of growth on blood agar, a-hemolytic streptococci are distinguished, surrounded by a small hemolysis zone with a greenish-grayish tint, P-hemolytic, surrounded by a transparent hemolysis zone, and non-hemolytic, not changing blood agar. However, the hemolytic sign turned out to be very variable, as a result of which it is used with caution for differential diagnostic purposes. Carbohydrate fermentation is not a stable and clear sign, as a result of which it is not used for differentiation and identification of streptococci. Streptococci are aerobes, do not form catalase, unlike staphylococci.

Antigens

Streptococci have several types of antigens that allow them to be differentiated from each other. According to R. Landsfield (1933), they are divided into 17 serogroups according to polysaccharide antigens, which are indicated by capital Latin letters A, B, C, D, E, F, etc. The most numerous serogroup A is the species S.pyogenes. Differentiation into serotypes is carried out according to the protein M-antigen. Now there are over 100 serotypes of serovar A streptococci. Some streptococci of this serogroup have cross-reactive antigens (CRAs). Antibodies to them react with myocardial muscle fibers, kidney tissue and other human organs. PRA can cause immunopathological conditions.

Ecology and epidemiology

Streptococci are relatively widespread in nature. On an ecological basis, they can be divided into several groups. The first group includes streptococci of serogroup A, pathogenic only for humans (S. pyogenes). The second group consists of pathogenic and opportunistic streptococci of serogroups B and D (S. agalactia, S. faccalis, etc.), pathogenic for humans and animals. The third ecological group is opportunistic oral streptococci (S. mutans, S. mitis, etc.). Thus, some streptococci cause only anthroponotic infections, while others cause anthropozoonotic infections. In the human body, streptococci live in ecological niches: the oral cavity, upper respiratory tract, skin and intestines. The source of infection are healthy bacteria carriers, convalescents and sick people. The main route of spread of the pathogen is airborne, less often contact. In the external environment, streptococci persist for several days. When heated to 50°C, they die in 10-30 minutes.

streptococcal infections

The Streptococcaceae family includes seven genera: Streptococcus; Enterococcus, Aerococcus, Pediococcus, Peptostreptococcus, Lactococcus, Leuconostoc. Among them, streptococci and enterococci are of the greatest importance in human infectious pathology. The classification of streptococci with Lensfield is generally accepted. Based on specific polysaccharides and surface protein antigens, 20 serological groups are distinguished, which are indicated by capital letters of the Latin alphabet from A to V. Pathogenic species belong to serogroups A, B, C and D, less often to groups F and J. they are determined using the reaction precipitation with appropriate antisera. However, due to the lack of precipitating sera, bacteriological laboratories are unable to carry out serological identification of streptococci. Therefore, in modern conditions, other criteria for their differentiation are used. The basis for the laboratory diagnosis of diseases caused by streptococci is bacteriological and serological methods.

Taking material for research

With sepsis, osteomyelitis and other types of generalized streptococcal infection, blood is taken. With others, pus, secretions of mucous membranes, sputum, cerebrospinal fluid, bile, urine, stool, etc. are taken, depending on the location of the pathological process. The rules for taking and delivering material to the laboratory are the same as for staphylococcal infections.

Primary microscopy

Primary microscopy of smears from manure, wound contents, mucosal secretions, etc. (except for blood) is carried out after staining them according to Gram. Streptococci are purple in color, look like short chains, diplococci or alone. Often, by the nature of the arrangement of cells in a smear, it is difficult or impossible at all to determine whether bacteria belong to streptococci. Therefore, it is necessary to isolate a pure culture and establish the type of pathogen.

Bacteriological research

To establish a diagnosis in acute streptococcal infections (with the exception of scarlet fever with a typical clinical picture), bacteriological examination should be carried out. If sepsis is suspected, 10-15 ml of blood is sown at the patient's bedside into a vial containing 100-150 ml of sugar broth (the ratio of blood and medium is 1:10). The best and most reliable results are obtained by blood cultures on Kitt-Tarozzi medium with semi-liquid agar. Anaerobic streptococci will also grow in it. Blood cultures are incubated in a thermostat at 37 ° C. With the growth of streptococci, a precipitate appears at the bottom of the medium. Gas can also form in the Kitt-Tarozzi medium. In smears from the sediment, gram-positive streptococci are found in the form of long chains. Pneumococci are located in short chains or in pairs in the form of lanceolate cells, returned to each other with thickened ends. For enterococci, a paired arrangement is characteristic, less often in tetrads or heaps, but in clusters. Individual cells of enterococci are polymorphic (large and small). In the absence of growth, the crops are kept in a thermostat for 3-4 weeks, periodically conducting bacterioscopy. The culture that has grown after bacterioscopy is subcultured into a blood agar dish to determine the type of hemolysis. After 18-20 hours, typical colonies grow, surrounded by a light zone (beta hemolysis) or a green zone (alpha hemolysis). Although the ability to hemolysis does not have an absolute diagnostic value, nevertheless, in the study of streptococci isolated from humans, non-hemolytic colonies of gamma-streptococci cannot be excluded. With very rare exceptions, they are not associated with infectious diseases. In order to better and more accurately identify isolated blood cultures of streptococci, colonies from blood agar are recommended to be screened for simple MPA, milk with methylene blue, bile broth (or bile blood agar). Hemolytic streptococci of serogroup A do not grow on simple and bile media, do not decolorize methylene blue in milk. Enterococci grow well on bile agar. Further, different types of streptococci can be differentiated by biochemical properties. But the biochemical signs of streptococci are not constant, which to some extent devalues ​​the use of these tests. plated on blood agar. The material is applied to the medium in a small amount, and then scattered with a loop or spatula with light strokes over the entire surface. It is not recommended to rub the studied material into agar. To increase the frequency of inoculation of streptococci, after inoculation on blood agar, tampons are immersed at the patient's bedside in a test tube with Kitty-Tarozzi medium, to which semi-liquid agar and 2-3 drops of defibrinated rabbit blood are added. The culture is incubated for 3-4 hours at 37 ° C, and then plated on blood agar plates, isolated and identified according to the usual scheme. For rapid identification of serogroup A beta-hemolytic streptococci, an express method is used using an immunofluorescence reaction. To do this, a smear from the isolated culture is fixed in 95% alcohol for 15 minutes, stained with the corresponding luminescent sera, and examined under a fluorescent microscope. Almost all group A hemolytic streptococci are sensitive to bacitracin and give a positive PIR test, and hydrolyze pyrrolidonyl-betanaphthylamide. Even faster, streptococci of this group are determined in swabs from the oropharynx and nasopharynx, processing them with modern commercial test kits. Group A antigens of streptococci are extracted with enzymes or other chemical reagents and determined in latex agglutination, coagglutination, or enzyme immunoassay. under the influence of disks containing staphylococcal beta-hemolysin). Further identification is carried out by serohypnosis in reactions of latex agglutination or coagglutination with commercial reagents or labeled monoclonal antibodies. Streptococci in vaginal smears can be quickly identified using the same test systems as for group A streptococci. To determine the virulence of isolated cultures of streptococci, a bioassay on white mice is used or the concentration of the surface M-protein, which is characteristic only for pathogenic strains, is determined. To do this, hydrochloric acid extracts are obtained from young cultures of streptococci and the content of M-antigen is determined in them. When determining alpha- and beta-hemolytic streptococci in the air of operating rooms, delivery rooms, rooms for newborns, manipulation rooms and other hospital premises, air is sown by the sedimentation method or with using the Krotov apparatus on the Garro medium (5% defibrinated blood and 0.2% aqueous 0.1% solution of gantzian violet are added to the melted MPA). Enterococci and saprophytic microflora do not grow on this medium.

Serological study

In chronic streptococcal infections, it is usually not possible to isolate the pathogen, especially with long-term treatment of patients with antibiotics and other antimicrobial drugs. In this case, serological studies are carried out: determination of streptococcal antigen in blood serum and urine, titration of antibodies to O-streptolysin, hyaluronidase and DNase. Streptococcal antigen is determined in the RSK. Antistreptococcal sera necessary for this are obtained by hyperimmunization of rabbits with a killed culture of beta-hemolytic streptococci of serogroup A. Antigen titer is considered to be the highest dilution of serum that delays hemolysis. The best results are obtained when setting the RSC in the cold. Recently, the ELISA method has been used quite successfully to detect streptococcal antigens in blood serum. When determining streptococcal antigens in the urine of patients, a precipitation reaction is used. The sediment of the morning portion of urine after centrifugation is treated with antistreptococcal precipitating serum. The result is taken into account after one hour at room temperature. Streptococcal antigens in blood serum and urine are often found in scarlet fever, tonsillitis, rheumatism. The determination of antibodies against O-streptolysin (antistreptolysin-O) is carried out by introducing a working dose of the standard preparation O-streptolysin into a number of test tubes with multiple dilutions of sera (1:25, 1: 50, 1:100, etc.). The mixture is incubated in a thermostat for 15 minutes, then 0.2 ml of a 5% suspension of rabbit erythrocytes is added to all test tubes and placed in a thermostat again for 60 minutes. In the presence of antistreptolysin in the blood of patients, hemolysis does not occur. The test tube with the highest dilution of serum, in which there is a pronounced delay in hemolysis, contains 0.5 AO (antitoxic units) of antistreptolysin-O. which is prepared from the umbilical cords of newborns. In the presence of anti-hyaluronidase, a clot forms in the tubes after the addition of acetic acid. The tube with the least amount of serum in which there is a clot containing 1 AO (antitoxic unit) of antihyaluronidase. With rheumatism and streptococcal glomerulonephritis, > 500 AO of antistreptolysin and > 800-1000 AO of antistreptohyaluronidase are detected in the blood serum from the first days of the disease. It is with these diseases that both serological reactions are most often carried out. In many countries, commercial test systems are used to detect antibodies to streptolysin, hyaluronidase, streptokinase, DNase, and other exoenzymes of streptococci.

Prevention and treatment

Specific prophylaxis of streptococcal infections has not been developed due to the ineffectiveness of the obtained vaccines and erythrogenic toxoid (against scarlet fever). A vaccine against caries is currently being developed. Treatment is carried out mainly with antibiotics. Resistance of streptococci to various antibiotics, including penicillin, develops slowly. This makes it possible to use many beta-lactam antibiotics, including benzylpenicillin. Of the other antibiotics, cephalosporins of the 1st and 2nd generations, aminoglycosides, and macrolides are used.

Streptococcal infections are a group of infectious diseases caused by streptococci of various serological groups, with airborne and alimentary transmission of the pathogen, occurring with fever, intoxication, local suppurative processes and the development of poststreptococcal autoimmune (rheumatism, glomerulonephritis) complications.

ICD-10 codes
A38. Scarlet fever.
A40. Streptococcal septicemia.
A40.0. Septicemia caused by group A streptococcus.
A40.1. Septicemia caused by group B streptococcus.
A40.2. Septicemia caused by group D streptococcus.
A40.3. Septicemia caused by Streptococcus pneumoniae.
A40.8. Other streptococcal septicemias.
A40.9. Streptococcal septicemia, unspecified.
A46. Erysipelas.
A49.1. Streptococcal infection, unspecified.
B95. Streptococci and staphylococci as the cause of diseases classified elsewhere.
B95.0. Group A streptococci as the cause of diseases classified elsewhere.
B95.1. Group B streptococci as the cause of diseases classified elsewhere.
B95.2. Group D streptococci as the cause of diseases classified elsewhere.
B95.3. Streptococcus pneumoniae as the cause of diseases classified elsewhere.
B95.4. Other streptococci as the cause of diseases classified elsewhere.
B95.5. Unspecified streptococci as the cause of diseases classified elsewhere.
G00.2. Streptococcal meningitis.
M00.2. Other streptococcal arthritis and polyarthritis.
R23.3. Congenital pneumonia caused by group B streptococcus.
R23.6. Congenital pneumonia caused by other bacterial agents (streptococcus, with the exception of group B).
P36.0. Neonatal sepsis due to group B streptococcus.
P36.1. Neonatal sepsis due to other and unspecified streptococci.
Z22.3. Carriage of pathogens of other specified bacterial diseases (streptococci).

Etiology (causes) of streptococcal infection

The causative agents are non-motile facultative anaerobic gram-positive cocci of the genus Streptococcus of the family Streptococcaceae. The genus includes 38 species differing in metabolic features, cultural and biochemical properties, and antigenic structure. Cell division occurs only in one plane, so they are arranged in pairs (diplococci) or form chains of different lengths. Some species have a capsule. Pathogens are capable of growth at a temperature of 25–45 °C; temperature optimum - 35–37 °С. On dense nutrient media, they form colonies with a diameter of 1–2 mm. On media with blood, colonies of some species are surrounded by a zone of hemolysis. An obligate sign that characterizes all representatives of the genus streptococci is negative benzidine and catalase tests. Streptococci are stable in the environment; for many months they are able to persist in dried pus or sputum.

Exciters withstand heating up to 60 °C for 30 minutes; under the influence of disinfectants die within 15 minutes.

According to the structure of group-specific polysaccharide antigens (substance C) of the cell wall, 17 serological groups of streptococci are distinguished, denoted by Latin letters (A–O). Within groups, streptococci are divided into serological variants according to the specificity of protein M-, P-, and T-antigens.

Group A streptococci have a wide range of superantigens: erythrogenic toxins A, B and C, exotoxin F (mitogenic factor), streptococcal superantigen (SSA), erythrogenic toxins (SpeX, SpeG, SpeH, SpeJ, SpeZ, SmeZ-2).

Superantigens are capable of interacting with major histocompatibility complex antigens expressed on the surface of antigen-presenting cells and with variable regions of the β-chain of T-lymphocytes, causing their proliferation and a powerful release of cytokines, TNF-α and γ-interferon. In addition, group A streptococcus is able to produce biologically active extracellular substances: streptolysins O and S, streptokinase, hyaluronidase, DNase B, streptodornase, lipoproteinase, peptidase, etc.

The cell wall of streptococcus includes a capsule, protein, polysaccharide (group-specific antigen) and mucoprotein layer. An important component of group A streptococci is protein M, which resembles the structure of the fimbria of gram-negative bacteria. The M protein (type-specific antigen) is the main virulence factor. Antibodies to it provide long-term immunity to re-infection, however, according to the structure of the M protein, more than 110 serological types are distinguished, which significantly reduces the effectiveness of humoral defense reactions. Protein M inhibits phagocytic reactions by directly acting on phagocytes, masking receptors for complement components and opsonins, and adsorbing fibrinogen, fibrin, and its degradation products on its surface. It has the properties of a superantigen, causing polyclonal activation of lymphocytes and the formation of antibodies with low affinity. Such properties play a significant role in the violation of tolerance to tissue iso-antigens and in the development of autoimmune pathology.

The properties of type-specific antigens are also possessed by the T-protein of the cell wall and lipoproteinase (an enzyme that hydrolyzes the lipid-containing components of the blood of mammals). Streptococci of different M-variants may have the same T-type or a complex of T-types. The distribution of serotypes of lipoproteinase exactly corresponds to certain M-types, but this enzyme is produced by about 40% of strains of streptococcus. Antibodies to T-protein and lipoproteinase do not possess protective properties. The capsule contains hyaluronic acid - one of the virulence factors. It protects bacteria from the antimicrobial potential of phagocytes and facilitates adhesion to the epithelium. Hyaluronic acid has antigen properties. Bacteria are able to destroy the capsule on their own when they invade tissues, synthesizing hyaluronidase. The third most important factor of pathogenicity is C5a-peptidase, which suppresses the activity of phagocytes. The enzyme cleaves and inactivates the C5a component of complement, which is a powerful chemoattractant.

Group A streptococci produce various toxins. Antibody titers to streptolysin O are of prognostic value. Streptolysin S exhibits hemolytic activity under anaerobic conditions and causes surface hemolysis on blood media. Both hemolysins destroy not only erythrocytes, but also other cells: streptolysin O damages cardiomyocytes, and streptolysin S damages phagocytes. Some strains of group A streptococci synthesize cardiohepatic toxin. It causes damage to the myocardium and diaphragm, as well as the formation of giant cell granulomas in the liver.

The bulk of group B streptococcal isolates are S. agalactiae. In recent years, they have increasingly attracted the attention of medical professionals. Group B streptococci commonly colonize the nasopharynx, gastrointestinal tract, and vagina.

There are the following serological variants of group B streptococci: Ia, Ib, Ic, II and III. Bacteria of serovars Ia and III are tropic to the tissues of the central nervous system and respiratory tract; often cause meningitis in newborns.

Among other species, pneumococci (S. pneumoniae) are of great diagnostic value, causing the majority of community-acquired pneumonia in humans.

Epidemiology of streptococcal infection

The reservoir and source of infection are patients with various clinical forms of acute streptococcal diseases and carriers of pathogenic streptococci. The greatest danger from an epidemiological point of view are patients whose foci are localized in the upper respiratory tract (scarlet fever, tonsillitis). They are highly contagious, and the bacteria they secrete contain the main virulence factors, the capsule and protein M. Infection from such patients most often leads to the development of a manifest infection in susceptible individuals.

Patients in whom foci of streptococcal infection are localized outside the respiratory tract (streptococcal pyoderma, otitis media, mastoiditis, osteomyelitis, etc.) are not so contagious, which is associated with a less active release of the pathogen from the body.

The duration of the contagious period in patients with acute streptococcal infection depends on the method of treatment. Rational antibiotic therapy of patients with scarlet fever and tonsillitis frees the body from the pathogen within 1.5–2 days. Drugs (sulfonamides, tetracyclines), to which group A streptococci have completely or partially lost their sensitivity, form a convalescent carriage in 40-60% of those who have been ill.

In communities where 15–20% of long-term carriers are present, streptococcus is usually constantly circulating. Carriage is considered dangerous for others with a microbial focus of more than 103 CFU (colony-forming units) per swab. The level of such carriage is significant - about 50% of healthy carriers of group A streptococci. Among cultures of the pathogen isolated from carriers, virulent strains are found several times less often than among strains isolated from patients. Carriage of streptococci of groups B, C and G in the pharynx is observed much less frequently than carriage of group A streptococci.

According to various sources, for 4.5–30% of women, the carriage of group B streptococci in the vagina and rectum is typical. The localization of the pathogen in the body largely determines the route of its elimination.

Mechanism of transmission- aerosol (airborne), less often - contact (food route and transmission through contaminated hands and household items). Infection usually occurs through close contact with a patient or a carrier for a long time. The causative agent is released into the environment most often during expiratory acts (coughing, sneezing, active conversation). Infection occurs by inhalation of the resulting airborne aerosol. Overcrowding indoors and prolonged close contact exacerbate the likelihood of infection.

At the same time, it should be taken into account that at a distance of more than 3 m, this transmission path is practically impossible.

The transmission factors of the pathogen are dirty hands, household items and infected food. Additional factors contributing to the transmission of the pathogen are low temperature and high humidity in the room.

Group A streptococci, getting into certain food products, are capable of reproduction and long-term preservation of virulent properties. So, outbreaks of tonsillitis or pharyngitis are known when using milk, compotes, butter, boiled egg salads, lobsters, shellfish, sandwiches with eggs, ham, etc.

The risk of developing purulent complications of streptococcal genesis are exposed to the wounded, burned, patients in the postoperative period, as well as women in labor and newborns. Autoinfection is possible, as well as the transmission of group B streptococci, which cause urogenital infections, through sexual contact. In the pathology of the neonatal period, the transmission factors are infected amniotic fluid. In 50% of cases, infection is possible during the passage of the fetus through the birth canal.

The natural susceptibility of people is high. Antistreptococcal immunity is antitoxic and antimicrobial in nature. In addition, there is a sensitization of the body by the type of HRT, which is associated with the pathogenesis of many post-streptococcal complications. Immunity in patients who have had a streptococcal infection is type-specific. It is possible to re-disease when infected with another serovar of the pathogen. Antibodies to the M protein are found in almost all patients from the 2nd–5th week of illness and within 10–30 years after the disease. Often they are determined in the blood of newborns, but by the 5th month of life they disappear.

Streptococcal infections are ubiquitous. In areas of temperate and cold climates, the incidence of pharyngeal and respiratory forms of infection is 5-15 cases per 100 people. In southern regions with a subtropical and tropical climate, skin lesions (streptoderma, impetigo) are of primary importance, the frequency of which among children in certain seasons reaches 20% or more. Minor injuries, insect bites, and poor skin hygiene predispose to their development.

Nosocomial streptococcal infection is possible in obstetric institutions; children's, surgical, otolaryngological, eye departments of hospitals. Infection occurs both endogenously and exogenously (from carriers of streptococci among staff and patients) through invasive diagnostic and treatment manipulations.

Cyclicity is one of the characteristic features of the epidemic process in streptococcal infections. In addition to the well-known cyclicity with an interval of 2–4 years, there is a periodicity with an interval of 40–50 years or more. The peculiarity of this undulation is in the emergence and disappearance of especially severe clinical forms. A significant number of cases of scarlet fever and tonsillopharyngitis are complicated by purulent-septic (otitis, meningitis, sepsis) and immunopathological (rheumatism, glomerulonephritis) processes. Severe generalized forms of infection with concomitant deep soft tissue lesions were previously referred to as "streptococcal gangrene". Since the mid 80s. in many countries, an increase in the incidence of streptococcal infection has been noted, which coincided with changes in the nosological structure of diseases caused by S. pyogenes. Again began to register group cases of severe generalized forms, often ending in death [toxic shock syndrome (TSS), septicemia, necrotizing myositis, fasciitis, etc.]. In the United States, 10-15 thousand cases of invasive streptococcal infection are recorded annually, of which 5-19% (500-1500 cases) are necrotizing fasciitis.

The widespread use of laboratory methods of research has made it possible to establish that the return of invasive streptococcal diseases is associated with a change in the pathogen serotypes circulating in the population: rheumatogenic and toxigenic serotypes have replaced M-serotypes. In addition, the incidence of rheumatic fever and toxic infections (toxic tonsillopharyngitis, scarlet fever and TSS) has increased.

In Russia in the late 80's - early 90's. the predominance of serotypes of the pathogen involved in the occurrence of severe generalized forms of infection was noted. Currently, 6-8 million cases of respiratory streptococcal infections are registered annually in Russia.

The economic cost of streptococcal infections and their consequences is about 10 times greater than that of viral hepatitis. Among the studied streptococcosis, the most economically significant are tonsillitis (57.6%), acute respiratory infections of streptococcal etiology (30.3%), erysipelas (9.1%), scarlet fever and active rheumatism (1.2%) and, finally, acute nephritis (0 .7%).

Diseases of primary streptococcal infection account for 50–80% of the seasonal incidence. The incidence of respiratory streptococcal infection has a pronounced autumn-winter-spring seasonality. The seasonal incidence rate is determined mainly by children attending preschool institutions.

The formation or renewal of organized teams and their numbers have a decisive influence on the timing of the seasonal increase in morbidity.

In organized collectives, updated once a year, a single seasonal increase in infection is observed. With a two-fold update, two-fold seasonal increases in the incidence are noted, especially characteristic of military groups. The first maximum incidence associated with the spring conscription is observed in June–July, the second, due to the autumn conscription, in December–January.

Measures to prevent streptococcal infection

In the absence of means of specific prevention of diseases transmitted by aerosols, with many erased and asymptomatic forms of infection, it is not so easy to reduce the incidence of streptococcal infection, therefore, anti-epidemic measures in organized groups are of particular importance.

The basis for the prevention of respiratory streptococcal infections in such groups is early and active diagnosis, isolation and full etiotropic treatment of patients. Preparations of the penicillin series prevent group diseases of scarlet fever and reduce the incidence of tonsillitis and streptococcal acute respiratory infections. To stop outbreaks of respiratory streptococcal diseases in organized groups, general emergency prophylaxis is carried out with penicillin preparations. To do this, all persons in contact with patients are given a single intramuscular injection of bicillin-5 (preschoolers - 750,000 IU, schoolchildren and adults - 1,500,000 IU) or bicillin-1 (preschoolers - 600,000 IU, schoolchildren and adults - 1,200,000 IU ). In military contingents belonging to high-risk groups for respiratory streptococcal infection, it is advisable to carry out emergency prophylaxis immediately after the formation of teams and before the start of the seasonal rise in the incidence (emergency preventive prophylaxis). In other groups, where seasonal rises in incidence are relatively low or not of a regular nature, an interrupting type of emergency prophylaxis can be used. In this case, it is carried out during the period of the epidemic rise in the incidence.

In organized children's and adult groups, hospital conditions, sanitary and hygienic measures (reducing the size of the team, its crowding, general sanitary measures, disinfection regimen) reduce the likelihood of airborne and contact-household transmission of the pathogen. Prevention of the alimentary route of infection is carried out in the same directions as with intestinal infections.

Activities in the epidemic focus

Decisive importance is attached to measures aimed at neutralizing the sources of infection (patients, convalescents, carriers) and preventing post-streptococcal complications. Treatment with penicillin drugs is carried out for ten days (WHO recommendations) - this is enough for the complete rehabilitation of patients as sources of infection and in order to prevent the development of post-streptococcal complications.

The pathogenesis of streptococcal infection

Most often, diseases occur after streptococci enter the mucous membranes of the pharynx and nasopharynx. Lipoteichoic acid, which is part of the cell wall, M- and F-proteins ensure the adhesion of the pathogen to the surface of the tonsils or other lymphoid cells. Protein M contributes to the resistance of bacteria to the antimicrobial potential of phagocytes, binds fibrinogen, fibrin and its degradation products. When streptococci multiply, toxins are released that cause an inflammatory reaction in the tissues of the tonsils. When streptococci enter the lymphatic tract through the lymph nodes, regional (angular) lymphadenitis occurs. Toxic components, penetrating into the blood, cause a generalized expansion of small vessels (clinically - hyperemia and punctate rash). An allergic component that disrupts vascular permeability is considered the cause of the development of glomerulonephritis, arthritis, endocarditis, etc. The septic component leads to the accumulation of the pathogen in various organs and systems and the development of foci of purulent inflammation. The presence of common cross-reacting antigenic determinants in group A streptococci (protein M, non-type-specific proteins, A-polysaccharide, etc.) and the sarcolemma of myofibrils of the heart and kidney tissues determines the development of autoimmune processes leading to rheumatism and glomerulonephritis. Molecular mimicry is the main pathogenetic factor of streptococcal infection in these diseases: antibodies to streptococcal antigens react with host autoantigens. On the other hand, protein M and erythrogenic toxin exhibit the properties of superantigens and cause T-cell proliferation, activating the cascade reaction of the effector link of the immune system and the release of mediators with cytotoxic properties: IL, TNF-α, interferon-gamma. Infiltration of lymphocytes and the local action of cytokines play an important role in the pathogenesis of invasive streptococcal infections (with cellulitis, necrotic fasciitis, skin lesions, internal organs). An important role in the pathogenesis of invasive streptococcal infection is assigned to TNF-α, LPS of its own gram-negative microflora and its synergistic interaction with the erythrogenic toxin S. pyogenes.

Clinical picture (symptoms) of streptococcal infection

Clinical forms of streptococcal infection. The clinical symptoms of streptococcal infections are diverse and depend on the type of pathogen, the localization of the pathological process and the condition of the infected organism.

Diseases caused by group A streptococci can be divided into primary, secondary and rare forms. The primary forms include streptococcal lesions of the ENT organs (tonsillitis, pharyngitis, acute respiratory infections, otitis media, etc.), skin (impetigo, ecthyma), scarlet fever, erysipelas. Among the secondary forms, diseases with an autoimmune mechanism of development (non-purulent) and toxic-septic diseases are distinguished. Secondary forms of the disease with an autoimmune mechanism of development include rheumatism, glomerulonephritis, vasculitis, and toxic-septic diseases - metatonsillar and peritonsillar abscesses, necrotic lesions of soft tissues, septic complications. Rare forms include necrotic fasciitis and myositis; enteritis; focal lesions of internal organs, TSS, sepsis, etc.

Clinical and laboratory signs of invasive streptococcal infection

The fall in systolic blood pressure to the level of 90 mm Hg. and below.
Multiorgan lesions involving two or more organs:
- kidney damage: creatinine in adults is equal to or greater than 2 mg / dl, and in children twice the age norm;
- coagulopathy: platelet count less than 100×106/l; increased intravascular coagulation; low content of fibrinogen and the presence of its decay products;
- liver damage: the age norm of the content of transaminases and total bilirubin is exceeded two times or more;
- acute RDS: acute onset of diffuse pulmonary infiltration and hypoxemia (with no signs of heart damage); increased capillary permeability; widespread edema (presence of fluid in the pleural or peritoneal area); decrease in the content of albumin in the blood;
- common erythematous spotted rash with desquamation of the epithelium;
- soft tissue necrosis (necrotizing fasciitis or myositis).
Laboratory criterion - isolation of group A streptococcus.

Cases of streptococcal infection are divided into:

probable - the presence of clinical signs of the disease in the absence of laboratory confirmation or when another pathogen is isolated; isolation of group A streptococcus from non-sterile body media;
confirmed - the presence of the listed signs of the disease with the release of group A streptococcus from the usually sterile environments of the body (blood, CSF,
pleural or pericardial fluid).

There are four stages in the development of an invasive form of streptococcal infection:

Stage I - the presence of a localized focus and bacteremia (in severe forms of tonsillopharyngitis and streptoderma, blood cultures are recommended);
Stage II - circulation of bacterial toxins in the blood;
Stage III - a pronounced cytokine response of the macroorganism;
Stage IV - damage to internal organs and toxic shock or coma.

Young people get sick more often. The invasive form of streptococcal infection is characterized by a rapid increase in hypotension, multiorgan lesions, RDS, coagulopathy, shock, and high mortality. Predisposing factors: diabetes mellitus, immunodeficiency states, diseases of the vascular system, the use of glucocorticoids, alcoholism, chickenpox (in children).

A provoking moment can be a minor superficial injury, hemorrhage into soft tissues, etc.

Necrotizing fasciitis (streptococcal gangrene)

Confirmed (established) case:
- soft tissue necrosis with involvement of the fascia;
- a systemic disease, including one or more signs: shock (drop in blood pressure below 90 mm Hg), disseminated intravascular coagulation, damage to internal organs (lungs, liver, kidneys);
- isolation of group A streptococcus from normally sterile environments of the body.
Supposed case:
- the presence of the first and second signs, as well as serological confirmation of streptococcal (group A) infection (4-fold increase in antibodies to streptolysin O and DNase B);
- the presence of the first and second signs, as well as histological confirmation of soft tissue necrosis caused by gram-positive pathogens.

Necrotizing fasciitis can be triggered by minor damage to the skin. External signs: swelling; erythema red, and then cyanotic; the formation of rapidly opening vesicles with a yellowish liquid. The process covers not only the fascia, but also the skin and muscles. On the 4-5th day, there are signs of gangrene; on the 7th–10th day - a sharp delineation of the affected area and detachment of tissues. Characterized by a rapid increase in symptoms, the development of early multi-organ (kidney, liver, lungs) and systemic lesions, acute RDS, coagulopathy, bacteremia, shock (especially in the elderly and people with concomitant diabetes mellitus, thrombophlebitis, immunodeficiency). A similar course of the process is also possible in practically healthy people.

streptococcal gangrene different from fasciitis of other etiologies. It is characterized by a transparent serous exudate, diffusely impregnating the flabby whitish fascia without signs of purulent fusion. Necrotizing fasciitis is distinguished from clostridial infection by the absence of crepitus and gas production.

Streptococcal myositis is a rare form of invasive streptococcal infection. The main symptom is severe pain that does not correspond to the severity of the external signs of the disease (swelling, erythema, fever, feeling of muscle strain). Characterized by a rapid increase in signs of local necrosis of muscle tissue, multiple organ lesions, acute distress syndrome, coagulopathy, bacteremia, shock. Lethality - 80–100%. TSS is a disease that poses a direct threat to life. In 41% of cases, the entrance gate of infection is a localized infection of soft tissues; lethality - 13%. Pneumonia is the second most common primary source of pathogen entry into the blood (18%); lethality - 36%. Invasive streptococcal infection in 8-14% of cases leads to the development of TSS (mortality - 33-81%). TSS caused by group A streptococcus is superior to TSS of other etiologies in terms of the severity of the clinical picture, the rate of increase in hypotension and organ damage, and the level of mortality. The rapid development of intoxication is characteristic.

Shock Symptoms occur after 4-8 hours and depend on the localization of the focus of the primary infection. For example, in the development of TSS in the presence of a deep skin infection involving soft tissues, the most common initial symptom is sudden intense pain (the main reason for seeking medical help). At the same time, objective symptoms (swelling, soreness) at the initial stages of the development of the disease may be absent, which causes erroneous diagnoses (flu, rupture of muscles or ligaments, acute arthritis, gout attack, deep vein thrombophlebitis, etc.). Cases of the disease with a fatal outcome in apparently healthy young people are described.

Severe pain, depending on its location, may be associated with peritonitis, myocardial infarction, pericarditis, pelvic inflammatory disease. Pain is preceded by an influenza-like syndrome: fever, chills, muscle pain, diarrhea (20% of cases). Fever is found in approximately 90% of patients; soft tissue infection leading to the development of necrotizing fasciitis in 80% of patients. In 20% of hospitalized patients, endophthalmitis, myositis, perihepatitis, peritonitis, myocarditis and sepsis may develop.

In 10% of cases, hypothermia is likely, in 80% - tachycardia, hypotension. All patients have progressive renal dysfunction, half of the patients have acute RDS. As a rule, it occurs already against the background of hypotension and is characterized by severe shortness of breath, severe hypoxemia with the development of diffuse pulmonary infiltrates and pulmonary edema. In 90% of cases, tracheal intubation and mechanical ventilation are necessary. More than 50% of patients experience disorientation in time and space; in some cases, coma may develop. In half of the patients who had normal blood pressure at the time of hospitalization, progressive hypotension is detected over the next 4 hours.

DIC often occurs.

Extensive necrotic changes in the soft tissues require surgical debridement, fasciotomy and, in some cases, amputation of the limbs. The clinical picture of shock of streptococcal genesis is distinguished by a certain torpidity and a tendency to persist, resistant to ongoing therapeutic measures (antibiotic therapy, administration of albumin, dopamine, saline solutions, etc.).

Kidney damage precedes the development of hypotension, which is characteristic only of streptococcal or staphylococcal toxic shock. Hemoglobinuria, an increase in creatinine by 2.5–3 times, a decrease in the concentration of albumin and calcium in the blood serum, leukocytosis with a shift to the left, an increase in ESR, and a decrease in hematocrit by almost two times are characteristic.

Lesions caused by group B streptococci occur in all age categories, but pathology of newborns dominates among them. 30% of children have bacteremia (without a specific focus of primary infection), 32–35% have pneumonia, and the rest have meningitis, often occurring within the first 24 hours of life. Diseases of newborns are severe, mortality reaches 37%. Meningitis and bacteremia are common in children, with 10–20% of children dying and 50% of survivors having residual impairment. Group B streptococci cause postpartum infections in puerperas: endometritis, urinary tract lesions, and complications of surgical wounds during caesarean section. In addition, group B streptococci can cause skin and soft tissue lesions, pneumonia, endocarditis, and meningitis in adults. Bacteremia is observed in elderly people suffering from diabetes mellitus, peripheral vascular disease and malignant neoplasms. Of particular note are streptococcal pneumonias that occur against the background of SARS.

Streptococci of serogroups C and G are known as the causative agents of zoonoses, although in some cases they can lead to local and systemic inflammatory processes in humans. Viridescent streptococci can cause bacterial endocarditis. Less significant, but incomparably more frequent pathology is carious lesions of the teeth caused by streptococci of the mutans biogroup (S. mutans, S. mitior, S. salivarius, etc.).

Diagnosis of streptococcal infection

Clinical diagnosis of streptococcal infections is often difficult.

The diagnosis of streptococcal pharyngeal and skin infections in all cases, except for scarlet fever and erysipelas, requires bacteriological studies with specific identification of the pathogen. For these purposes, express methods for identifying group A streptococci are used, with the help of which it is possible to diagnose an acute streptococcal infection within 15–20 minutes without first isolating a pure culture of the pathogen.

At the same time, the isolation of streptococci does not always indicate their involvement in pathology due to the widespread healthy carriage.

True infections caused by group A streptococci always initiate the development of a specific immune response, accompanied by a significant increase in antibody titer to one of the extracellular streptococcal antigens - streptolysin O, deoxyribonuclease B, hyaluronidase, or nicotinamide adenine dinucleotidease. These diagnostic methods are of practical importance in acute rheumatism and glomerulonephritis.

Along with the determination of the titer of antistreptococcal antibodies, the detection of circulating antigens (free or in immune complexes) plays an important role in establishing the role of streptococci in the formation of immunopathological processes. The basis of modern diagnostic methods is ELISA and the use of antisera to discrete antigens of group A streptococci.

Medical therapy

For the treatment of all diseases caused by group A streptococci, benzylpenicillin preparations are used, to which the pathogen remains highly sensitive. Most strains are also highly sensitive to erythromycin, azithromycin, clarithromycin, oxacillin, and oleandomycin.

In invasive streptococcal infections, benzylpenicillin (intravenously or intramuscularly, 2.4 million units every 4 hours) and clindamycin (intravenously or intramuscularly, 0.6–1.2 g every 6 hours) are prescribed. Treatment of TSS with antibiotics is not always effective (mortality reaches 50%). Normal human immunoglobulin containing a wide range of neutralizing antibodies to streptococcal superantigens is effective.