- streptococcal infections
- Morphology, biology of streptococcus
- Antigenic structure; classification
- Laboratory diagnosis of streptococcal infections
1. Streptococcus (Streptococcus) - causative agents of a large number of human and animal infections, they call erysipelas, sepsis and purulent infections, scarlet fever, tonsillitis. There are non-pathogenic varieties that live in the human mouth and intestines. Anaerobic strains of streptococci have a low degree of activity, and they are usually found in the human oral cavity and digestive tract. In some cases, they cause chronic inflammatory processes and are the causative agents of wound infections. Significantly more important in the pathogenesis of human streptococcal infections are facultative anaerobes, which divided according to the nature of hemolysis on blood agar into the following types:
- beta-hemolytic streptococci;
- alpha-hemolytic streptococci;
- gamma-hemolytic streptococci that do not cause visible hemolysis on solid nutrient media with blood.
The greatest pathogenicity possess beta-hemolytic streptococci, which are the causative agents of most streptococcal infections in humans. pathogenicity alpha-hemolytic streptococci less pronounced. They are found in the pharyngeal mucus of healthy people, but in some cases in chroniosepsis, subacute septic endocarditis, oral infections. Gamma hemolytic streptococci - saprophytes of the upper respiratory tract and human intestinal tract. In some cases, they cause subacute septic endocarditis, urinary tract infections, wound infections.
2. Streptococcus morphology: these are immobile spherical or oval cocci with a diameter of 0.8-1 microns, forming chains of various lengths and positively staining by Gram. Some strains form a capsule. The length of the chains is related to the growing conditions. In a liquid nutrient medium, they are longer; on dense media, they are often arranged in the form
short chains and bundles. Cocci may be ovoid before division. The division occurs perpendicular to the chain. Each coccus is divisible by 2.
Biology of streptococci, cultural properties: on blood agar, streptococcus forms small (1-2 mm in diameter) translucent rods, grayish or colorless, which are well removed by a loop. The size of the hemolysis zone varies in different strains: group A forms a hemolysis zone slightly larger than the diameter of the colony, group B gives a large hemolysis zone. Type A streptococci form a greenish or greenish-brown hemolysis zone, cloudy or transparent, varying in size and color intensity. In some cases, the colony itself acquires a greenish coloration. In liquid nutrient media, streptococci are characterized by benthic, often rising along the walls, growth. When shaken, a granular or flaky suspension. Common growing media: meat-peptone agar with the addition of rabbit or sheep blood, semi-liquid agar with serum.
Good growth and toxin formation can be ensured by "combination broth" or on media containing casein hydrolyzate and yeast extract. Hemolytic streptococci metabolize glucose with the formation of lactic and other acids, which is a factor limiting the growth of microbes in a nutrient medium. Resistance to physical and chemical factors.
Group A hemolytic streptococci can persist for a long time on objects, in dust in a dried state. However, these cultures, while maintaining viability, lose their virulence.
Group A streptococcus is highly sensitive to penicillin, which has a bactericidal effect on it. Sulfanilamide acts on streptococcus A bacteriostatically.
3. Modern classification of streptococci based on their serological differences. Known 17 serological groups: BUT, AT,
C, D, E, F, etc. The division into groups is based on the presence of a specific polysaccharide (substance C) in representatives of different groups. Group A streptococci are pathogenic for humans. Streptococci of different groups differ not only in their ability to cause diseases in humans and animals and in their natural habitat, but also in biochemical and cultural characteristics.
In addition to serological differences, when differentiating strains, take into account the following indications:
- source of selection;
- nature of hemolysis;
- the ability to form soluble hemolysis;
- resistance to various temperatures;
- feature to grow in milk with methylene blue;
- fermentation of sugars;
- liquefaction of gelatin.
Serological serotypes: By agglutination on glass, strains of beta-hemolytic streptococcus isolated from scarlet fever and other streptococcal infections and from healthy carriers were divided into 50 serological types. Cultures of 46 types are assigned to group A, types 7, 20, 21 - to group C, and type 16 - to group D.
Division streptococci into types produced with the help precipitation reactions. The results of type determination by the agglutination reaction and in the precipitation reaction usually give the same results. Scarlet fever usually predominates
1 or 2-3 types. Common antigenic substances were found in strains belonging to groups A, C, Q.
Streptococcal (with scarlet fever) toxin contains
2 factions:
- thermolabile or true scarlatinal toxin;
- thermostatic, which has the properties of an allergen.
The true erythrogenic toxin is a protein. It is a streptococcal exotoxin that causes Dick reaction in people susceptible to scarlet fever. Purified erythorogenic toxin is used for skin tests to determine the level of antitoxic immunity. (Dick reaction).
4. For bacteriological research the material collected with a swab from the pharyngeal and nasal mucosa is inoculated on a Petri dish with blood agar, placed in a thermostat for 3-4 hours at 37 °C. In the presence of streptococci, characteristic rods grow on the agar in a day. For microscopic examination, an isolated colony is inoculated into a liquid nutrient medium (meat-peptone broth with whey) and after 24 hours of cultivation in a thermostat is subjected to research. Smears stain according to Gram or methylene blue by Leffler. Then, the biochemical properties of the cultures are studied and the type of streptococcus is determined using an agglutination test on glass and a precipitation test with typical sera. From serological reactions use the complement fixation reaction (RCC) with the serum of an immunized rabbit.
Streptococcus (Streptococcus) was first isolated from the tissues of people with erysipelas and with wound infections in 1874 by T. Billroth, and described in sepsis by L. Pasteur in 1879 and A. Ogston in 1881. A pure culture of streptococci was isolated and studied F. Feleisen (1883) and A. Rosenbach (1884).
Pathogenic streptococci in animals and humans inhabit the mucous membranes, skin and show their pathogenicity with a decrease in the overall resistance of the animal organism or individual tissues (in case of injury, burns, etc.).
Under natural conditions, streptococci are pathogens in cattle and horses, as well as suppurative processes. In piglets and birds, they cause a septic disease - streptococcosis. Sometimes cause complications of viral and bacterial infections.
Antigens. The modern classification is based on the definition of the antigenic structure of streptococci, which makes it possible to subdivide all streptococci into 17 serological groups, denoted by Latin letters in alphabetical order. Serogroups A, B, C, D, E, F are of practical interest. Group A is the causative agent of a large number of infections in humans; group B - causative agents of mastitis in cows; groups B, C, D, E - pathogens of infections in animals of different species. The antigen that makes it possible to divide streptococci into serogroups is a polysaccharide (C-substance), which is part of the cell wall of streptococci.
The chemical nature of streptococcal antigens varies. In group A, they are protein antigens M, R and T.
Toxin formation. Pathogenic streptococci produce exotoxins of various effects.
Hemolysin causes the destruction of erythrocytes, leukocytes, platelets, macrophages; when administered intravenously to rabbits, it causes hemoglobinemia and hematuria.
Leukocidin destroys leukocytes or inhibits their phagocytic properties.
A lethal toxin (necrotoxin) causes necrosis when administered intradermally to a rabbit. Parenchymal organs and other tissues may be exposed to necrotic action.
In addition to exotoxins, pathogenic streptococci produce enzymes hyaluronidase, fibrinolysin, deoxyribonuclease, ribonuclease, neuraminidase, proteinase, streptokinase, amylase, lipase, as well as endotoxins, which are characterized by thermal stability. Exotoxins, for example, are thermolabile: hemolysin is inactivated at a temperature of 55 "C for 30 minutes, leukocidin - at 70 ° C. Fibrinolysin is the most heat-resistant, not destroyed by boiling for up to 50 minutes.
Myta is a wake-up caller. Streptococcus equi was discovered by Schutz in 1888. Myt is a contagious disease predominantly of young hoofed animals (up to two years old), characterized by catarrhal-purulent inflammation of the mucous membrane of the upper respiratory tract, submandibular and pharyngeal lymph nodes.
Morphology. Smears are stained according to Gram and Romanovsky-Giemsa. For Str. equi in pus (mytny abscess, nasal discharge) is characterized by the arrangement of long chains of cocci flattened across, in smears from agar and broth cultures, the pathogen looks like short chains, sometimes two cocci. Does not form capsules or spores. Motionless. The size of cocci is 0.6-1.0 microns. Gram positive.
Cultivation. To isolate a pure culture, inoculation is carried out on serum-glucose agar (it does not grow on ordinary media). After 24 hours on agar, mytaceous streptococcus forms small, translucent, dew-like colonies. Colonies merge with each other.
On blood agar, growth in the form of small colonies with a zone of /3-hemolysis. On clotted blood serum Str. equi forms glassy grayish colonies. In whey broth and Kitt-Tarozzi medium, growth is noted in small grains lining the walls and bottom of the test tube, the broth remains transparent.
biochemical properties. Mytny streptococcus does not coagulate plain milk, litmus and methylene milk does not discolor (does not reduce), does not ferment lactose, sorbitol, mannitol. The absence of fermentation of these carbohydrates makes it possible to differentiate mytaceous streptococcus from pyogenic streptococcus (Str. pyogenes), which ferments lactose, coagulates milk, and reduces methylene blue.
Toxin formation. Weakly expressed.
Antigenic structure. Str. equi belong to serogroup C. They contain polysaccharide C, synthesize extracellular antigens (toxins), O - streptolysin (protein) and S - streptolysin (lipid-protein complex). All of them are capable of causing the destruction of red blood cells.
Sustainability. In wet pus it lasts up to 6 months, in manure - one month. When heated to 70 °C, it dies within 1 hour, at 85 °C - in 30 minutes. As disinfectants, a 1% formalin solution, a 2% sodium hydroxide solution are used at an exposure of 10-30 minutes.
Pathogenicity. Mytom affects young hoofed animals, cats and mice. Streptococci that have fallen on the nasal mucosa reach the submandibular lymph nodes via the lymphogenous route. Under the influence of cocci and their toxins, inflammation of the mucous membrane occurs, first serous, and then mucopurulent.
Mine streptococcus isolated directly from pus is virulent in foals, but cultures of this streptococcus freshly isolated on serum or blood agar are avirulent. Toxin formation is weakly expressed. The reason for this phenomenon has not been studied.
Laboratory diagnostics. Pathological material (mucous discharge from the nasal openings, purulent exudate or punctate of the submandibular lymph nodes), sent to the laboratory, is examined according to the general scheme: smear microscopy; inoculation of the received material on nutrient media to isolate a pure culture of streptococci and their identification; biological test - on white mice, cats, especially kittens. The latter die from one ten-millionth dose of broth culture when infected subcutaneously within 3-10 days.
Differentiation. An isolated culture (pure) can be identified using a soap antivirus. In this filtrate Sir. equi does not grow, but other types of streptococci do. With an atypical form of myt, RSK with a myt antigen is used.
Mytnaya streptococcus, unlike pyogenic streptococcus, does not ferment milk, lactose, sorbitol, mannitol (Table 1).
tab. 1 Differentiation of streptococci
Designations: "—" - does not ferment; "+" - ferments.
Immunity and biological products. Animals that have been ill with mytom acquire strong immunity (most often for life). Vaccines from killed cultures of streptococci do not induce immunity. The anti-wash serum has not been used either due to its high cost.
As a specific treatment, an antivirus is used, which is a filtrate of a 20-day broth culture of Str. equi, made from local strains of streptococcus. In sick animals, the drug is administered subcutaneously in the upper third of the neck at a dose of 50-100 ml, depending on the weight and age of the animal. Injections are best done in several places. In the absence of a noticeable effect, the antivirus is administered again in a day or two. The drug can be used for compresses and washing abscesses. With hyperplasia of the submandibular and parotid lymph nodes, the antivirus is injected subcutaneously in the area of \u200b\u200bthese nodes.
The causative agent of mastitis. Mastitis in cattle is caused by various microorganisms, but the most common causative agent is Streptococcus agalactiae (Streptococcus mastitidis).
Morphology. Str. agalactiae - small, 0.5-l µm in diameter, slightly flattened or oval cocci, located in long chains (several tens of cocci). In smears from cultures. grown on dense nutrient media, mastitis streptococcus forms short chains. Does not form spores or capsules. It stains well with all aniline dyes, it is gram-positive (color table 1).
Cultivation. Streptococcus mastitis is an aerobe. Grows poorly on normal nutrient media. It is well cultivated on media supplemented with defibrinated blood or blood serum. In serum, MPB grows as a fine-grained precipitate, while the medium remains clear. On blood MPA, it forms small (dotted) shiny grayish colonies surrounded by a zone of hemolysis (type 3 hemolysis).
A pure culture of streptococcus is obtained by inoculation of the modified secretion from the affected udder lobe on blood MTIA in bacteriological dishes with a daily incubation at 37 ° C, followed by subculture of a colony typical of this microbe on whey meat-peptone broth and blood agar.
biochemical properties. Mastitis streptococcus does not dilute meat-peptone gelatin and curdled whey, does not discolor methylene milk, litmus milk partially changes. Ferments with the formation of acid glucose, lactose, sucrose, maltose, salicin. Does not ferment sorbitol and dulcit.
To determine the potential hemolytic activity of mastitis streptococci, CAMP (CAMP) is used - a method that got its name from the initial letters of the names of Australian researchers: Christie, Atkins and Munh-Peterson.
The method is based on an increase in the hemolytic activity of group B streptococcus in a zone close to the hemolysis band of staphylococcus on blood agar; hemolytic, but having lost or reduced hemolytic activity, strains of agalactic streptococcus form a noticeable zone of hemolysis near staphylococcus aureus.
Toxin formation. Mastitis streptococcus produces toxins: erythrotoxin, hemolysin, necrotoxin, leukocidin - and enzymes: fibrinolysin and hyaluronidase.
Antigenic structure. Str. agalactiae belongs to serogroup B.
Sustainability. In the dried purulent exudate remains 2-3 months. When heated to 85 ° C, it dies in 30 minutes. Freezing preserves it. Sensitive to oxytetracycline, polymyxin in combination with sulfadimezin.
3% sodium hydroxide solution, 1% formalin solution neutralize mastitis streptococcus in 10-15 minutes.
Pathogenicity. The most virulent streptococci are found in cows with acute mastitis. Purulent exudate from the udder of such animals at a dose of 0.1-0.2 ml kills mice with intraperitoneal infection during the day.
Laboratory diagnostics and differentiation. The material for the study is the milk of mastitis cows, which are sown on MPA, MPA and blood agar.
The resulting culture is identified taking into account morphological, cultural, hemolytic properties and antigenic structure, which is determined in the reaction of diffuse precipitation in agar gel or by the method of fluorescent antibodies with specific sera.
Immunity. Due to antitoxic and antibacterial factors.
Biopreparations. They are not here. For treatment, antibiotics and sulfonamides are used, which are injected through the nipple canal into the milk tank.
pyogenic streptococcus. Str. pyogenes causes abscesses, arthritis, cellulitis, endometritis, and septicemia in animals. The occurrence of purulent processes is facilitated by a reduced resistance of the body, untimely surgical treatment of wounds, non-compliance with the rules of asepsis and antisepsis, excessive trauma to tissues during the study of wounds, hypovitaminosis and beriberi.
Morphology. In smears Str. pyogenes is a short chain of 3-5 cells. It stains well with solutions of conventional aniline dyes. Gram-positive. Does not form spores or capsules.
Cultivation. Grows well on media with glucose or serum. On MPA grows in the form of small round colonies; on blood agar around colonies of Str. pyogenes, a small zone of /3-gmolysis is formed. When growing in the BCH, it forms turbidity.
biochemical properties. Coagulates milk, causes reduction of litmus milk, decolorizes methylene milk. Ferments lactose, sorbitol, mannitol.
Laboratory diagnostics. During bacteriological examination of the material (purulent exudate of wounds, abscesses, aseptically taken exudate, blood - if septicemia is suspected), smears are prepared. To isolate a pure culture of Str. pyogenes are cultured on nutrient media.
Biopreparations. Active immunization methods have not been developed. Treatment is carried out with the help of antibiotics, more often in combination with sulfonamides, nitrofurans, with the help of enzymes, streptococcal bacteriophage, etc.
The causative agent of diplococcal infection. Str. pneumoniae was isolated in 1871 by L. Pasteur from the saliva of a child who died of rabies. In pure culture, pneumococci were isolated in 1886 by Frenkel and Vekselbaum, who established the role of pneumococcus in the etiology of lobar pneumonia.
Pneumococci are widely distributed in nature. In healthy animals, they are found on the mucous membranes of the respiratory tract, digestive tract, and genital organs. In cows, sheep, pigs, goats, horses, due to violation of zootechnical standards of keeping and inadequate feeding during pregnancy after childbirth, latent carriage of pneumococci turns into a clinically pronounced disease - mastitis and endometritis develop.
Calves, lambs, piglets, infected from their mothers, become a source of the infectious agent for the rest of the young, which leads to the development of enzootics. Infection occurs through the gastrointestinal tract and respiratory tract. The disease is characterized by septicemia, damage to the lungs (lobular pneumonia) and the gastrointestinal tract.
Morphology. In smears from pathological material, streptococci are oval in shape and arranged in pairs or in short chains. In chronic processes, cells have the form of diplostreptococcus. Cell sizes are 0.8–1.25 µm. In smears from fresh cultures, the diplococcal form predominates. Motionless. Dispute does not form.
In the body, pneumococci form a well-defined capsule, which is lost during cultivation on artificial nutrient media, but is preserved on media with serum or blood.
Cultivation. Pneumococci reproduce under aerobic and anaerobic conditions at 36-38°C and pH 7.2-7.6. For their cultivation, media containing 0.5% glucose and 5% animal blood are used. On MPA they form small transparent colonies with a blue tint; in MPB - turbidity; on serum agar, small transparent colonies appear, resembling dew drops. Colonies of freshly isolated cultures of diplococcus on blood agar are small, round, transparent, surrounded by a zone of a-hemolysis (green zone), in semi-liquid agar - flaky growth, in gelatin - growth by injection without liquefaction.
biochemical properties. Ferment with the formation of acid glucose, lactose, sucrose, mannitol; do not ferment arabinose and dulcit; do not form pigment and indole.
Toxin formation. On semi-liquid agar with blood and maltose, a toxin is produced that causes fatal poisoning of kittens when administered orally.
Antigenic structure. In the characterization of species specificity, the nucleoprotein antigen has a certain significance. which is located deep in the cytoplasm of pneumococci. Closer to the cell surface is a species-specific somatic polysaccharide C-antigen. On the surface of the cytoplasm is a type-specific protein M-antigen.
Inside the view Str. pneumoniae, there are 84 serovars that are agglutinated only by the corresponding type sera.
The antigenic structure of pneumococci can change rapidly under the influence of various physical and chemical factors, which is accompanied by the formation of transitional and then rough colonies on agar, loss of capsules, virulence, hemolytic and immunogenic qualities, as well as an increase in biochemical activity.
Sustainability. Diplococcus is not very stable. Heating at 55°C causes the death of the culture after 10 minutes. In the external environment dies within 3-4 weeks. Formalin, sodium hydroxide, lime are used as disinfectants. Pneumococci easily undergo autolysis due to the high activity of their intracellular enzymes.
Pathogenicity. White mice and rabbits are most sensitive to pneumococci. Subcutaneous administration of small doses of culture causes the death of mice from septicemia within 12-36 hours. Infection with weakly virulent cultures develops long-term chronic diseases. Pathogenic pneumococci are also for large and small cattle, dogs, rats and other animals.
Diplococcus is pathogenic for mice, rabbits, piglets, lambs, calves, and when injected into the nipple of the mammary gland - for sheep, pigs, cows.
The most virulent cultures of pneumococcus, isolated from the corpses of young animals that died from diplococcal infection (with toxicoseeptic form). Toxins are specific, t. neutralized only by antidiplococcal serum.
Laboratory diagnostics. The corpses of young animals or parenchymal organs, tubular bones, joints, heart blood in sealed pipettes, and the brain are sent to the laboratory. If diplococcal endometritis or mastitis is suspected in adult animals, genital secretions and milk are examined.
The diagnosis is made on the basis of microscopic examination of the isolation of a pure culture and the results of bioassays.
The bioassay is placed on white mice, which, after intraperitoneal or subcutaneous infection, die after 16-48 hours.
Serological method. Streptococcal antigens in the blood are detected in the complement fixation reaction with immune rabbit sera (according to V. I. Ioffe); in the urine in the precipitation reaction (according to I. M. Lyampert). Determine the presence of antihyaluronidase and antistreptolysin in the blood to diagnose nephritis. O-Streptolysin has the ability to lyse rabbit erythrocytes. In the presence of antibodies (anti-O-streptolysins) in serum, erythrocyte lysis does not occur.
In addition, for typing diplococci, an agglutination reaction and an immunofluorescence method are used, which makes it possible to identify streptococci in a mixed population of microbes if this population is treated with a fluorescent antiserum against streptococci.
Immunity is accompanied by a latent carriage of diplococci in animals.
Biopreparations. For the specific prevention of diplococcal infection, a semi-liquid formol vaccine, anti-diplococcal serum (K. P. Chepurov, 1950), a polyvalent formol alum vaccine against salmonellosis, pasteurellosis and diplococcosis of piglets (A. G. Malyavin, 1956) are used.
Penicillin, biomycin, tetracycline, oxytetracycline, polymyxin M are used, which are effective agents against diplococci both in acute septic cases and in subacute, chronic and complicated pneumonia.
Taxonomy and classification
Kingdom: Procaryotae;
Department: Firmicutes;
Family: Streptococcaceae;
Genus: Streptococcus;
Species: group A, S. pyogenes;
group B, S. agalactiae;
group C, S. equisimilis;
group D (enterococci) - S. faecalis, S. faecium, S. durans;
group G, S. anginosus.
Does not have a group antigen - S. salivarius, S. mitis, S. mutans, S. pneumoniae.
Morphology and tinctorial properties
Streptococci are ovoid in shape, cell diameter is about 1 µm, immobile, asporogenic, have a capsule. S. pneumoniae forms a polysaccharide macrocapsule in the body.
In the smear, they are arranged in the form of chains of cocci.
They stain well with aniline dyes and are Gram-positive.
Biological properties
Chemoorganotrophs, facultative anaerobes. Demanding on nutrient media. Mesophiles.
Culture media: sugar MPA, sugar MPA, blood MPA, serum MPA and serum MPA. On liquid nutrient media, they give near-bottom or parietal growth; on blood MPA - small, non-pigmented colonies with a zone of complete hemolysis (β-hemolysis in S. pyogenes); 10% HSA growth does not give (difference from staphylococcus aureus).
Biochemical properties
Catalase-negative. Oxidase negative. Carbohydrates of the short variegated Hiss series are fermented to acid; glucose and mannitol - only under anaerobic conditions (unlike staphylococcus aureus); do not ferment inulin (unlike pneumococcus).
Antigens
The classification of streptococci according to their antigenic structure was developed by R. Lancefield. According to the polysaccharide of the cell wall (substance S), streptococci are divided into 20 serological groups, denoted by capital letters of the Latin alphabet from A to V. Within the serogroups, serovars are isolated according to the specificity of protein antigens M, P and T. Serovars are numbered.
Classification of streptococci by antigenic structure
Pathogenicity factors of group A streptococci
I. Toxins (exotoxins):
O-streptolysin;
S-streptolysin;
leukocidin;
· cytotoxins;
erythrogenic toxin;
pyrogenic toxin.
II. Enzymes:
hyaluronidase;
streptokinase (fibrinolysin);
DNase;
proteinase.
III. Structural components:
Capsule (groups A and B streptococci);
lipoteichoic acids, cell wall proteins;
· M-protein.
IV. Cross-reactive antigens (CRA). Examples:
hyaluronic acid of streptococci is similar to the tissue of the tubules of the kidneys à glomerulonephritis;
· M-protein of streptococci is similar in antigenic properties to myocardial myosin à myocarditis;
Streptococcal polysaccharide cross-reacts with cardiac valve glycoproteins à endocarditis.
Epidemiology pathogenesis and clinic of the disease (features)
Streptococci are representatives of the microflora of the skin, oral mucosa, upper respiratory tract, intestines (enterococci), genital tract (S. agalactiae) of a person.
Many of them are conditionally pathogenic microorganisms and cause various pathological processes only when the immune defense is weakened.
Source of infection: sick person or carrier.
Mechanisms and ways of transmission: airborne and contact.
Caused diseases: 1) purulent-septic infections; 2) tonsillitis (tonsillitis); 3) scarlet fever; 4) erysipelas; 5) rheumatism; 6) glomerulonephritis;
7) carriage.
Microbiological diagnostics
Test material: pus, mucus, sputum, blood, urine, cerebrospinal fluid, etc.
I. Bacterioscopic method.
Gram-stained smear microscopy - Gram-positive cocci arranged in chains.
II. bacteriological method.
Method steps:
1. Sowing on sugar BCH (accumulation medium) - near-bottom or parietal growth.
2. Sowing on blood MPA - small non-pigmented colonies with a zone of complete hemolysis (β-hemolysis in S. pyogenes).
3. Cleavage of suspicious colonies on a joint of whey or sugar MPA in order to accumulate a pure culture.
4. Checking the purity of the isolated culture - microscopy of Gram-stained smears (homogeneous population of Gram-positive cocci arranged in short or long chains).
5. Statement of diagnostic tests for the difference between the families of Streptococcaceae and Micrococcaceae: oxidase (-), catalase (-), coagulase (-), lecithinase (-), anaerobic fermentation of glucose and mannitol.
6. Differentiation of species
7. Intraspecific differentiation (Table "Tests for the difference between S. pyogenes and S. pneumoniae").
Determination of the serogroup in the precipitation reaction. Definition of antibiogram.
III. Serological method. Statement of immunological reactions (RSK) for the determination of antibodies - antistreptolysin; antistreptodernase, etc.
Immunity
Antimicrobial and antitoxic. After scarlet fever, unlike other streptococcal infections, a strong antitoxic immunity remains. Its tension is checked by staging an intradermal test with an erythrogenic toxin (Dick's test).
In the absence of immunity, Dick's test is positive; in the presence of antitoxin - negative.
Prevention and treatment
Specific prevention of streptococcal infections has not been developed. Autovaccines can be used to prevent chronic infections. For treatment, antibiotics of the penicillin series, sulfa drugs are used.
End of work -
This topic belongs to:
Lecture course in microbiology
Educational institution.. Gomel State Medical University.. Department of Microbiology, Virology and Immunology..
If you need additional material on this topic, or you did not find what you were looking for, we recommend using the search in our database of works:
What will we do with the received material:
If this material turned out to be useful for you, you can save it to your page on social networks:
| tweet |
All topics in this section:
Staphylococci
Taxonomy: Kingdom: Procaryotae; Department: Firmicutes; Family: Micrococcaceae; Genera: Staphylococcys (typical), Micrococcus, Planococcus,
Streptococcus pneumoniae
Morphology and tinctorial properties Pneumococcus lanceolate, diplococcus, about 1 micron in size, asporogenic, immobile. Has a polysaccharide capsule. Aniline stains well
Lecture 15
Enterobacteria - a characteristic of the family. Escherichia. Shigella. Salmonella. Yersinia. The family Enterobacteriaceae unites an extensive group of facultative anaerobic bacteria.
General principles for diagnosing infections caused by microbes of the Enterobacteriaceae family
The microscopic diagnostic method, as a rule, is not used, since pathogenic and non-pathogenic enterobacteria have common morphological properties. Bacteriological method
Escherichia
Taxonomy Kingdom: Procaryotae; Division: Gracilicutes; Family: Enterobacteriaceae; Genus: Escherichia; Species: Escherichia coli. Within the species by O-, H- and K (B) - ant
Shigella
Bacterial dysentery (shigellosis) is an intestinal anthroponotic infection caused by bacteria of the genus Shigella, occurring with a predominant lesion of the mucous membrane of the large intestine.
Salmonella
Salmonellosis is an acute intestinal infection caused by various serotypes of bacteria of the genus Salmonella, characterized by a variety of clinical manifestations from asymptomatic
Typhoid fever
Epidemiology Typhoid fever belongs to intestinal anthroponoses. Humans are the only source and reservoir of infection. The source of infection is most often chronic
Salmonella
Epidemiology Animals are the primary source of Salmonella: cattle, pigs, waterfowl, chickens, synanthropic rodents and a large number of other animals. Dopol
Generalized form of infection)
Laboratory diagnostics Test material: vomit, gastric lavage, feces, food residues. I. Bacteriological method. Method steps:
Yersinia
Taxonomy Kingdom Procaryotae, department Gracilicutes, family Enterobacteriaceae, genus Yersinia Currently, the genus Yersinia includes 10 species. Species with
Lecture 16
Especially dangerous infections of bacterial etiology. Etiology, pathogenesis, immunity, prevention of cholera, plague, tularemia, brucellosis, anthrax. To the category of persons
Vibrios
Cholera is an acute anthroponotic infectious disease that occurs with the development of dehydration and demineralization as a result of vomiting and watery diarrhea. Taxonomy and classification
Yersinia
Plague is an acute natural focal, transmissible, zooanthroponotic disease. It is characterized by fever, severe intoxication, serous-hemorrhagic inflammation of the lymphatic
francisella
Tularemia is a zoonotic, natural focal disease that occurs with intoxication, fever, lymphadenitis, damage to various organs, a diverse clinical picture.
Brucella
Brucellosis is a zoonotic infectious-allergic disease prone to a chronic course. Occurs with prolonged undulating fever, lesions of the musculoskeletal system, cardiovascular
The causative agent of anthrax
Anthrax is an acute bacterial zoonotic infection characterized by intoxication, the development of serous-hemorrhagic inflammation of the skin, lymph nodes and internal organs.
The causative agent of whooping cough
Morphology Small, ovoid bacillus, 0.5x1.2 microns in size, asporogenic, has a delicate capsule (B. pertussis) is immobile. Only B. bronchiseptica has mobility. Gram negative
Haemophilus influenzae
Diseases caused by H. influenzae: meningitis, pneumonia, osteomyelitis, sepsis, otitis media, sinusitis, conjunctivitis.
Legionella
Legionellosis is a disease of bacterial etiology that occurs with intoxication, respiratory syndrome, severe pneumonia and damage to the central nervous system. Excitement
Pseudomonas aeruginosa
Taxonomy Kingdom Procaryotae, division Gracilicutes, family Pseudomonadaceae, genus Pseudomonas, species Pseudomonas aeruginosa. The genus Pseudomonas contains more than 140
Acinetobacter baumannii
Taxonomy Kingdom Procaryotae, department Gracilicutes, family Moraxellaceae, genus Acinetobacter, species Acinetobacter baumannii. Morphology: gram-negative immobile
Stenotrophomonas maltophilia
Taxonomy Kingdom Procaryotae, department Gracilicutes, family Xanthomonadaceae, genus Stenotrophomonas, species: Stenotrophomonas maltophilia. Morphology
Mycobacteria
Tuberculosis (from Latin tuberculum - tubercle) is a chronic infectious-allergic disease with a specific lesion of the respiratory, osteoarticular, genitourinary systems
Listeria
Listeriosis is a zoonotic infection characterized by a predominant lesion of the mononuclear phagocyte system. Taxonomy Kingdom Procaryotae, Division Firmi
corynebacteria
Diphtheria is an acute infectious disease characterized by fibrinous inflammation of the mucous membranes of the pharynx, larynx, trachea, less often other organs, intoxication phenomena, with predominantly
Clostridia
Bacteria of the genus Clostridium are large Gr+ rods with terminal, subterminal, or central spores; the diameter of the spore exceeds the diameter of the cell, so the rod with the spore has
Tetanus
Tetanus (tetanus) is a wound infection caused by C. tetani, characterized by damage to the nervous system, attacks of tonic and clonic convulsions. Morphological properties.
Botulism
Botulism - enteric clostridium, one of the forms of food poisoning - is a severe food poisoning and intoxication that occurs as a result of eating foods containing
gas gangrene
Gas gangrene is a polymicrobial wound infection characterized by severe intoxication, rapid tissue necrosis (necrosis) with gas formation and the development of edema in them. WHO
Lecture 20
Curved bacteria. Spirochetes and other spiral bacteria. Microbiological diagnosis of relapsing fever, relapsing tick-borne fever, Lyme borreliosis and leptospirosis. Laboratory diagnostic methods
Borrelia
Epidemic relapsing fever is an anthroponotic, transmissible disease with alternating periods of fever and apyrexia, accompanied by enlargement of the liver and spleen.
Pathogenesis and clinic
Bacteria that enter the body are captured by phagocytes and multiply in their cytoplasm. By the end of the incubation period, Borrelia in large numbers are in the bloodstream, where they are destroyed under
Lyme borreliosis
Epidemiology Source and reservoir of infection - small and large rodents, deer, birds, cats, dogs, sheep, cattle. Transmission route - transmissible through bites
Leptospira
Leptospirosis is an acute natural focal zoonotic infectious disease that occurs with intoxication, myalgia, damage to the kidneys, liver, nervous and vascular systems.
Treponema
Syphilis is a chronic sexually transmitted disease with a variable cyclic course, affecting all organs and tissues. Pathogenic types of treponema: T.pallidum
Campylobacter
Campylobacteriosis is an acute infectious zoonotic disease characterized by a syndrome of general intoxication, a predominant lesion of the gastrointestinal tract and possible
Lecture 21
Pathogenic rickettsia and chlamydia Rickettsia are prokaryotes endowed with similarities to viruses. They have in common with viruses: a) absolute intracellular pa
The causative agent of North Asian rickettsiosis
The causative agent of North Asian rickettsiosis R. sibirica was identified as a separate species of rickettsiae by a group of Russian scientists led by P.F. Zdrodovsky in 1938 when studying endemic foci
The causative agent of Q fever
Q fever is an acute transmissible febrile disease that occurs with symptoms of interstitial pneumonia (pneumorickettsiosis) and differs from rickettsiosis in the absence of
Pathogenic chlamydia
Taxonomy Kingdom Procaryotae, division Gracilicutes, order Chlamydiales, family: Chlamydiaceae. Genera: Chlamydia, Chlamydophila Species: Chlamydia trachomatis, Chl
Lecture 22
General virology. Principles of diagnosis, specific prevention and therapy of viral infections. Antiviral immunity. The subject of study of the section of medical virology is epidemiological
Ecology of viruses and epidemiology of viral infections
Viruses are devoid of protein-synthesizing systems, they are autonomous genetic structures forever tied to the internal environment of the body - from the simplest prokaryotic cell to the human body
Nonspecific protective factors. Interferons
Interferons (IFN) are powerful inducible proteins that can be produced in any vertebrate nuclear cell. Four main actions of interferon are known: antiviral, immune
Lecture 23
Viruses - causative agents of SARS: orthomyxoviruses, paramyxoviruses, coronaviruses, rubella virus. Respiratory infections caused by viruses are commonly referred to as acute respiratory infections.
Type A influenza virus
The virion is spherical in shape with a complex supercapsid diameter of 80-120 nm; in freshly isolated from diseased materials, filamentous forms several micrometers long are found. The supercapsid contains two glyco
Influenza virus type C
The virion has the same form as viruses of types A and B. The genome is represented by a single-stranded negative RNA of 7 fragments, the nucleotide sequence of which differs significantly from those of viruses
Respiratory coronaviruses
The family of coronaviruses (Coronaviridae) includes one genus Coronavirus, which includes complex viruses with varying degrees of polymorphism. They are usually round or oval in shape. diame
Reoviruses
The Reoviridae family includes three genera - Reovirus or Orthoreovirus (virus of vertebrates), Rotavirus (viruses of vertebrates) and Orbivirus (viruses of vertebrates, but also reproduce in insects). semeys
Lecture 24
Viruses - causative agents of acute intestinal infections: picornaviruses, caliciviruses, coronaviruses, reoviruses, astroviruses. Acute intestinal diseases (ACI) are the second most common after
Enteroviruses
The main role in the etiology of viral ACD, or diarrhea, is played by enteroviruses and rotaviruses. The genus Enterovirus belongs to the Picornaviridae family. The family includes the smallest and most
Coxsackie viruses
In terms of virological and epidemiological properties, they are in many ways similar to polioviruses and play a significant role in human pathology. Coxsackieviruses according to the nature of the pathogenic effect on suckling mice
ECHO viruses
In 1951, other viruses were discovered that differ from polio viruses in the absence of pathogenicity for monkeys, and from Coxsackie viruses in the absence of pathogenicity for newborn mice. Infusion
Rotaviruses
Human rotavirus was first discovered in 1973 by R. Bishop et al. using the method of immune electron microscopy, and their etiological role was proved in experiments on volunteers. Genus
Caliciviruses
They were first isolated from animals in 1932, and in 1976 they were found in the feces of children suffering from acute gastroenteritis. Now they are separated into an independent family - Caliciviridae.
Astroviruses
They were discovered in 1975 during an electron microscopic examination of the feces of 120 children under the age of 2 years suffering from gastroenteritis. On electron microscopy, the virion had a typical star
Lecture 25
Ecological group of arbo- and roboviruses. rhabdoviruses. Under the name "arboviruses" (from lat. Arthropoda - arthropods and English borne - born, transmitted) is currently a pony
Alpha viruses
The genus alpha viruses includes 21 serotypes (according to some sources - 56). They are divided into 3 antigenic groups: 1) western equine encephalomyelitis virus complex (including Sindbis virus),
Flaviviruses
The Flaviviridae family includes two genera. Genus Flavivirus - causative agents of encephalitis and causative agents of hemorrhagic fevers. The genus Hepacivirus is the causative agent of hepatitis C. Many flaviviruses are
Yellow fever
Yellow fever is an acute severe infectious disease, which is characterized by severe intoxication, two-wave fever, severe hemorrhagic syndrome, kidney and liver damage. Because of
Dengue fever
There are two independent clinical forms of this disease: 1. Dengue fever, characterized by fever, severe pain in the muscles and joints, as well as leukopenia and forms
Bunyaviruses
The Bunyauiridae family (from the name of the locality Bunyamvera in Africa) is the largest in terms of the number of viruses included in it (over 250). Classification of the family Bunyauiridae 1. Bunyav
Crimean hemorrhagic fever
It is found in the south of Russia and in many other countries. Infection occurs through tick bites, as well as through household contact. The virus was isolated by M.P. Chumakov in 1944 in the Crimea. Lethality enough
filoviruses
The Filoviridae family includes the Marburg and Ebola viruses. They have the appearance of filamentous formations, sometimes U-shaped, sometimes "6" shaped. The Marburg virion is 790 nm long and the Ebola virion is 970 nm.
Viral hepatitis A
Viral hepatitis A is a human infectious disease characterized by a predominant lesion of the liver and manifested clinically by intoxication and jaundice. Hepatitis A virus was discovered in 1973
Viral hepatitis E
The causative agent - hepatitis E virus (HEV) - is non-enveloped, with a cubic symmetry type, has a spherical shape with spikes and depressions on the surface. Today it is an unclassified
Viral hepatitis B
Hepatitis B is the most dangerous form of hepatitis among all known forms of viral hepatitis. Its causative agent is the hepatitis B virus (HBV). For the first time, the antigen of the virus
Viral hepatitis C
The causative agent - hepatitis C virus (HCV) - belongs to the Flaviviridae family, genus Hepacavirus. The virion (55-60nm in diameter) has a supercapsid. The genome is represented by single-stranded plus RNA. HCV proteins - three
Hepatitis G virus
Hepatitis G virus has been included in the Flaviviridae family, genus Hepacavirus, but in the latest classification it has been reclassified as an unclassified virus. The virus genome is a single-stranded RNA
Lecture 27
Retroviruses. Slow infections. Retroviruses - the family got its name from the English. Retro - back, back, since virions contain reverse transcriptase,
Slow infections
Slow infections are the main symptoms. 1. Unusually long (months and years) incubation period. 2. Slowly progressive nature of the course. 3. Unusual pores
Lecture 28
DNA genomic viruses. oncogenic viruses. DNA-genomic viruses replicate predominantly in the cell nucleus. They are less variable than RNA genomic ones, persist for a long time
Herpesviruses
Composition of the Herpesviridae family Alphaherpesvirinae HSV-1 (HSV-1) HSV-2 (HSV-2) HSV-3 (VZV-3) Betaherpesvirinae CMV 5 (CMV)
Adenoviruses
The first representatives of the adenovirus family were isolated in 1953 by W. Rowe and co-authors from the tonsils and adenoids of children, in connection with which they received this name. The family Adenoviridae is divided into
Papillomaviruses
The Papillomaviridae family was isolated from the Papovaviridae family in 2002. Includes about 120 serotypes of viruses, which are divided into groups: non-oncogenic, HPV 1,2,3,5 oncogenic
Viral carcinogenesis
Oncogenic viruses contain oncogenes - v-onc. Human, mammalian, and bird cells contain their precursors - c-onc, called proto-oncogenes (20-30 genes).
Morphology of mushrooms
Fungi are multicellular or unicellular non-photosynthetic eukaryotic microorganisms with a cell wall. Fungi have a nucleus with a nuclear membrane, a cytoplasm with organelles, a cytoplasm
Physiology of mushrooms
Mushrooms are incapable of photosynthesis, immobile and have thick cell walls, which deprives them of the ability to actively absorb nutrients. Absorption of nutrients from the environment
Dermatophytes
Dermatophytes - fungi from the genera Trichophyton, Microsporum and Epidermophyton - are the causative agents of dermatophytosis. These infections, according to various sources, affect from one third to half of the world's population.
The causative agent of sporotrichosis
The causative agent of sporotrichosis (a disease of gardeners) is a dimorphic fungus Sporothrix schenckii, which lives in the soil and on the surface of plants, various types of wood. Infection may be limited to
The causative agents of respiratory endemic mycoses
Respiratory endemic mycoses are a group of infections caused by dimorphic fungi that live in the soil of certain geographical areas, and the respiratory mechanism of infection (through
The causative agent of histoplasmosis
The causative agent of histoplasmosis is Histoplasma capsulatum (Ascomycota division). Ecology and epidemiology There are two varieties of H. capsulatum species. First, N. capsulatum var
The causative agent of blastomycosis
The causative agent of blastomycosis (Gilchrist's disease) is the dimorphic fungus Blastomyces dermatitidis. Ecology and epidemiology The causative agents of histoplasmosis are in a close genus
Causative agents of candidiasis
The causative agents of candidiasis are about 20 species of yeast fungi from the genus Candida (imperfect yeast from the Ascomycota department). The main types of pathogens of candidiasis: C. albicans, C. parapsilo
Conditionally pathogenic (opportunistic) microbes
This is a large and systematically heterogeneous group of microbes that cause diseases in humans under certain conditions. In modern human pathology, etiological
pathogenicity
Most obligate pathogenic microbes have specific entry gates. Their natural entry into other biotopes does not lead to the development of infection. Opportunistic microbes are capable of
Opportunistic infections are characterized by the following features
1. Polynosology. The causative agents of opportunistic infections do not have a strictly pronounced organ tropism: the same species can be the cause of the development of various nosological forms (bronchitis
General principles of microbiological diagnosis of opportunistic infections
The main diagnostic method at present is bacteriological, which consists in isolating a pure culture of the pathogen and determining the necessary for therapeutic and prophylactic purposes with
Stages of the diagnostic process in clinical microbiology
The diagnostic process in clinical microbiology consists of four main stages: 1. formulation of the problem and choice of research method; 2. choice, taking the studied mat
General rules for the collection, storage and transfer of material
The results of diagnostics of many microbial diseases largely depend on the correct choice of material and compliance with the following conditions for its collection, delivery, storage and processing. 1. Kind of mate
streptococci
Streptococci belong to the family Streptococcaceae(genus Streptococcus). They were first discovered by T. Billroth in 1874 with erysipelas; L. Pasteur - in 1878 with postpartum sepsis; isolated in pure culture in 1883 by F. Feleisen.
Streptococcus (gr. . streptos- chain and coccus- grain) - gram-positive, cytochrome-negative, catalase-negative cells of spherical or ovoid shape with a diameter of 0.6 - 1.0 microns, grow in the form of chains of various lengths (see color incl., Fig. 92) or in the form of tetracocci; immobile (except for some representatives of serogroup D); the content of G + C in DNA is 32 - 44 mol % (for the family). Dispute does not form. Pathogenic streptococci form a capsule. Streptococci are facultative anaerobes, but there are also strict anaerobes. The temperature optimum is 37 ° C, the optimum pH is 7.2 - 7.6. On conventional nutrient media, pathogenic streptococci either do not grow or grow very poorly. For their cultivation, sugar broth and blood agar containing 5% defibrinated blood are usually used. The medium should not contain reducing sugars, as they inhibit hemolysis. On the broth, the growth is near-wall in the form of a crumbly sediment, the broth is transparent. Streptococci, forming short chains, cause turbidity of the broth. On dense media, serogroup A streptococci form colonies of three types: a) mucoid - large, shiny, resemble a drop of water, but have a viscous consistency. Such colonies form freshly isolated virulent strains having a capsule;
b) rough - larger than mucoid, flat, with an uneven surface and scalloped edges. Such colonies form virulent strains having M antigens;
c) smooth, smaller colonies with smooth edges; form virulent cultures.
Streptococci ferment glucose, maltose, sucrose and some other carbohydrates to form acid without gas (except S. kefir, which forms acid and gas), milk does not coagulate (except S. lactis), do not possess proteolytic properties (except for some enterococci).
Streptococcus classification. The genus Streptococcus includes about 50 species. Among them, 4 pathogens are distinguished ( S. pyogenes, S. pneumoniae, S. agalactiae and S. equi), 5 opportunistic and more than 20 opportunistic species. For convenience, the entire genus is divided into 4 groups using the following features: growth at 10 °C; growth at 45°C; growth on a medium containing 6.5% NaCl; growth on a medium with a pH of 9.6;
growth on a medium containing 40% bile; growth in milk with 0.1% methylene blue; growth after heating at 60 °C for 30 min.
Most pathogenic streptococci belong to the first group (all of these signs are usually negative). Enterococci (serogroup D), which also cause various human diseases, belong to the third group (all of the listed signs are usually positive).
The simplest classification is based on the ratio of streptococci to erythrocytes. Distinguish:
obin, see tsv. on, fig. 93b);
S. viridans(green streptococci);
Serological classification has gained great practical importance. Streptococci have a complex antigenic structure: they have a common antigen for the whole genus and various other antigens. Among them, group-specific polysaccharide antigens localized in the cell wall are of particular importance for classification. According to these antigens, at the suggestion of R. Lansfeld, streptococci are divided into serological groups, denoted by the letters A, B, C, D, F, G, etc. Now 20 serological groups of streptococci are known (from A to V). Streptococci pathogenic for humans belong to group A, to groups B and D, less often to C, F and G. In this regard, the determination of the group affiliation of streptococci is a decisive moment in the diagnosis of the diseases they cause. Group polysaccharide antigens are determined using the appropriate antisera in the precipitation reaction.
In addition to group antigens, type-specific antigens were found in hemolytic streptococci. In group A streptococci, they are proteins M, T and R. The M protein is thermostable in an acidic environment, but is destroyed by trypsin and pepsin. It is detected after hydrochloric acid hydrolysis of streptococci using a precipitation reaction. Protein T is destroyed when heated in an acidic environment, but is resistant to the action of trypsin and pepsin. It is determined using the agglutination reaction. The R antigen is also found in streptococci of serogroups B, C, and D. It is sensitive to pepsin, but not to trypsin, and is destroyed by heating in the presence of acid, but stable by moderate heating in a weak alkaline solution. According to the M-antigen, hemolytic streptococci of serogroup A are divided into a large number of serovariants (about 100), their determination is of epidemiological significance. According to the T-protein, serogroup A streptococci are also divided into several dozen serovariants. In group B, 8 serovariants are distinguished.
Streptococci also have cross-reactive antigens common to the antigens of the cells of the basal layer of the epithelium of the skin and the epithelial cells of the cortical and medullary zones of the thymus, which may be the cause of the autoimmune disorders caused by these cocci. In the cell wall of streptococci, an antigen (receptor II) was found, with which their ability, like staphylococci with protein A, is associated, to interact with the Fc fragment of the IgG molecule.
Diseases caused by streptococci divided into 11 classes. The main groups of these diseases are as follows: a) various suppurative processes - abscesses, phlegmon, otitis media, peritonitis, pleurisy, osteomyelitis, etc.;
b) erysipelas - wound infection (inflammation of the lymphatic vessels of the skin and subcutaneous tissue);
c) purulent complications of wounds (especially in wartime) - abscesses, phlegmon, sepsis, etc.;
d) angina - acute and chronic;
e) sepsis: acute sepsis (acute endocarditis); chronic sepsis (chronic endocarditis); postpartum (puerperal) sepsis;
e) rheumatism;
g) pneumonia, meningitis, creeping ulcer of the cornea (pneumococcus);
h) scarlet fever;
i) dental caries - its causative agent is most often S. mutans. The genes of cariogenic streptococci responsible for the synthesis of enzymes that ensure the colonization of the surface of teeth and gums by these streptococci have been isolated and studied.
serogroup D occi (enterococci) are recognized as causative agents of wound infections, various purulent surgical diseases, purulent complications in pregnant women, puerperas and gynecological patients, infect the kidneys, bladder, cause sepsis, endocarditis, pneumonia, food poisoning (proteolytic variants of enterococci). Streptococcus serogroup B ( S. agalactiae) often cause diseases of the newborn - respiratory tract infections, meningitis, septicemia. Epidemiologically, they are associated with the carriage of this type of streptococcus in the mother and staff of maternity hospitals.
Anaerobic streptococci ( Peptostreptococcus), which are found in healthy people as part of the microflora of the respiratory tract, mouth, nasopharynx, intestines and vagina, can also be the culprits of purulent-septic diseases - appendicitis, postpartum sepsis, etc.
The main pathogenicity factors of streptococci.
1. Protein M is the main factor of pathogenicity. M-proteins of streptococcus are fibrillar molecules that form fimbriae on the surface of the cell wall of group A streptococci. M-protein determines adhesive properties, inhibits phagocytosis, determines antigenic type-specificity and has superantigen properties. Antibodies to the M-antigen have protective properties (antibodies to T- and R-proteins do not have such properties). M-like proteins have been found in group C and G streptococci and may be factors in their pathogenicity.
2. Capsule. It consists of hyaluronic acid, similar to that which is part of the tissue, so phagocytes do not recognize encapsulated streptococci as foreign antigens.
3. Erythrogenin - scarlet fever toxin, superantigen, causes TSS. There are three serotypes (A, B, C). In patients with scarlet fever, it causes a bright red rash on the skin and mucous membranes. It has a pyrogenic, allergenic, immunosuppressive and mitogenic effect, destroys platelets.
4. Hemolysin (streptolysin) O destroys erythrocytes, has a cytotoxic, including leukotoxic and cardiotoxic, effect, it is formed by most streptococci of serogroups A, C and G.
5. Hemolysin (streptolysin) S has a hemolytic and cytotoxic effect. Unlike streptolysin O, streptolysin S is a very weak antigen, it is also produced by streptococci of serogroups A, C and G.
6. Streptokinase is an enzyme that converts the preactivator into an activator, and it converts plasminogen into plasmin, the latter hydrolyzes fibrin. Thus, streptokinase, by activating blood fibrinolysin, increases the invasive properties of streptococcus.
7. The factor that inhibits chemotaxis (aminopeptidase) inhibits the mobility of neutrophilic phagocytes.
8. Hyaluronidase is an invasion factor.
9. Clouding factor - hydrolysis of serum lipoproteins.
10. Proteases - destruction of various proteins; possibly associated with tissue toxicity.
11. DNases (A, B, C, D) - DNA hydrolysis.
12. The ability to interact with the Fc fragment of IgG using the II receptor - inhibition of the complement system and phagocyte activity.
13. Pronounced allergenic properties of streptococci, which cause sensitization of the body.
Streptococcus resistance. Streptococci tolerate low temperatures well, are fairly resistant to desiccation, especially in a protein environment (blood, pus, mucus), and remain viable for several months on objects and dust. When heated to a temperature of 56 ° C, they die after 30 minutes, except for group D streptococci, which can withstand heating to 70 ° C for 1 hour. A 3-5% solution of carbolic acid and lysol kills them within 15 minutes.
Features of epidemiology. The source of exogenous streptococcal infection are patients with acute streptococcal diseases (tonsillitis, scarlet fever, pneumonia), as well as convalescents after them. The main method of infection is airborne, in other cases direct contact and very rarely alimentary (milk and other food products).
Features of pathogenesis and clinic. Streptococci are inhabitants of the mucous membranes of the upper respiratory tract, digestive and genitourinary tracts, so the diseases they cause can be endogenous or exogenous in nature, that is, they are caused either by their own cocci or as a result of infection from the outside. Having penetrated through damaged skin, streptococci spread from the local focus through the lymphatic and circulatory systems. Infection by airborne or airborne dust leads to damage to the lymphoid tissue (tonsillitis), regional lymph nodes are involved in the process, from where the pathogen spreads through the lymphatic vessels and hematogenously.
The ability of streptococci to cause various diseases depends on:
a) places of entrance gate (wound infections, puerperal sepsis, erysipelas, etc.; respiratory tract infections - scarlet fever, tonsillitis);
b) the presence of various pathogenicity factors in streptococci;
c) the state of the immune system: in the absence of antitoxic immunity, infection with toxigenic streptococci of serogroup A leads to the development of scarlet fever, and in the presence of antitoxic immunity, tonsillitis occurs;
d) sensitizing properties of streptococci; they largely determine the peculiarity of the pathogenesis of streptococcal diseases and are the main cause of such complications as nephronephritis, arthritis, damage to the cardiovascular system, etc.;
e) pyogenic and septic functions of streptococci;
f) the presence of a large number of serogroup A streptococci serogroup A by M-antigen.
Antimicrobial immunity, which is caused by antibodies to the M protein, is type-specific in nature, and since there are a lot of serovariants for the M-antigen, repeated infections with tonsillitis, erysipelas and other streptococcal diseases are possible. More complex is the pathogenesis of chronic infections caused by streptococci: chronic tonsillitis, rheumatism, nephritis. The following circumstances confirm the etiological role of serogroup A streptococci in them:
1) these diseases, as a rule, occur after acute streptococcal infections (tonsillitis, scarlet fever);
2) in such patients, streptococci or their L-forms and antigens in the blood are often found, especially during exacerbations, and, as a rule, hemolytic or green streptococci on the mucous membrane of the throat;
3) constant detection of antibodies to various antigens of streptococci. Especially valuable diagnostic value is the detection in patients with rheumatism during an exacerbation in the blood of anti-O-streptolysins and anti-hyaluronidase antibodies in high titers;
4) the development of sensitization to various streptococcal antigens, including the thermostable component of erythrogenin. It is possible that autoantibodies to the connective and renal tissues, respectively, play a role in the development of rheumatism and nephritis;
5) the obvious therapeutic effect of the use of antibiotics against streptococci (penicillin) during rheumatic attacks.
Postinfectious immunity. The main role in its formation is played by antitoxins and type-specific M-antibodies. Antitoxic immunity after scarlet fever has a strong long-term character. Antimicrobial immunity is also strong and long lasting, but its effectiveness is limited by the type specificity of M antibodies.
Laboratory diagnostics. The main method for diagnosing streptococcal diseases is bacteriological. The material for the study is blood, pus, mucus from the throat, plaque from the tonsils, wound discharge. The decisive step in the study of isolated pure culture is the determination of its serogroup. For this purpose, two methods are used.
A. Serological - determination of a group polysaccharide using a precipitation reaction. For this purpose, appropriate group-specific sera are used. If the strain is beta-hemolytic, its polysaccharide antigen is extracted with HCl and tested with antisera from serogroups A, B, C, D, F, and G. If the strain does not cause beta-hemolysis, its antigen is extracted and tested with antisera from groups B and D only. Groups A, C, F, and G antisera often cross-react with alpha-hemolytic and non-hemolytic streptococci. Streptococci that do not cause beta hemolysis and do not belong to groups B and D are identified by other physiological tests (Table 20). Group D streptococci have been identified as a separate genus. Enterococcus.
B. Grouping method - based on the ability of aminopeptidase (an enzyme produced by streptococci of serogroups A and D) to hydrolyze pyrrolidine-naphthylamide. For this purpose, commercial kits of the necessary reagents are produced for the determination of group A streptococci in blood and broth cultures. However, the specificity of this method is less than 80%. Serotyping of serogroup A streptococci is performed using either precipitation (determine M-serotype) or agglutination (determine T-serotype) reaction for epidemiological purposes only.
Of the serological reactions, coagglutination and latex agglutination reactions are used to detect streptococci of serogroups A, B, C, D, F and G. Determination of the titer of anti-hyaluronidase and anti-O-streptolysin antibodies is used as an auxiliary method for diagnosing rheumatism and for assessing the activity of the rheumatic process.
IFM can also be used to detect streptococcal polysaccharide antigens.
PNEUMOCOCCIS
Special position in the genus Streptococcus takes the form S. pneumoniae which plays a very important role in human pathology. It was discovered by L. Pasteur in 1881. Its role in the etiology of lobar pneumonia was established in 1886 by A. Frenkel and A. Weikselbaum, as a result of which S. pneumoniae called pneumococcus. Its morphology is peculiar: cocci have a shape resembling a candle flame: one
Table 20
Differentiation of some categories of streptococci
Note: + – positive, – negative, (–) – very rare signs, (±) – changeable sign; b aerococci - Aerococcus viridans, is found in approximately 1% of patients suffering from streptococcal diseases (osteomyelitis, subacute endocarditis, urinary tract infections). Separated into an independent species in 1976, not studied enough.
the end of the cell is pointed, the other is flattened; usually arranged in pairs (flat ends facing each other), sometimes in the form of short chains (see color incl., fig. 94b). They do not have flagella, they do not form spores. In humans and animals, as well as on media containing blood or serum, they form a capsule (see color inc., Fig. 94a). Gram-positive, but often Gram-negative in young and old cultures. facultative anaerobes. The temperature optimum for growth is 37 °C, at temperatures below 28 °C and above 42 °C they do not grow. The optimal pH for growth is 7.2 - 7.6. Pneumococci form hydrogen peroxide, but they do not have catalase, so for growth they require the addition of substrates containing this enzyme (blood, serum). On blood agar, small round colonies are surrounded by a green zone formed as a result of the action of the exotoxin hemolysin (pneumolysin). Growth in sugar broth is accompanied by turbidity and a slight precipitation. In addition to the O-somatic antigen, pneumococci have a capsular polysaccharide antigen, which is very diverse: according to the polysaccharide antigen, pneumococci are divided into 83 serovariants, 56 of them are divided into 19 groups, 27 are presented independently. Pneumococci differ from all other streptococci in morphology, antigenic specificity, and also in that they ferment inulin and are highly sensitive to optochin and bile. Under the influence of bile acids in pneumococci, intracellular amidase is activated. It breaks the bond between alanine and peptidoglycan muramic acid, the cell wall is destroyed, and pneumococcal lysis occurs.
The main factor in the pathogenicity of pneumococci is the capsule of a polysaccharide nature. Capsular pneumococci lose their virulence.
Pneumococci are the main causative agents of acute and chronic inflammatory diseases of the lungs, which occupy one of the leading places in the incidence, disability and mortality of the population around the world.
Pneumococci along with meningococci are the main culprits of meningitis. In addition, they cause creeping corneal ulcers, otitis, endocarditis, peritonitis, septicemia and a number of other diseases.
Post-infectious immunity type-specific, due to the appearance of antibodies against a typical capsular polysaccharide.
Laboratory diagnostics based on isolation and identification S. pneumoniae. The material for the study is sputum and pus. White mice are very sensitive to pneumococci, so a biological sample is often used to isolate pneumococci. In dead mice, pneumococci are found in a smear preparation from the spleen, liver, lymph nodes, and when sowing from these organs and from the blood, a pure culture is isolated. To determine the serotype of pneumococci, an agglutination reaction on glass with typical sera or the phenomenon of “capsule swelling” is used (in the presence of homologous serum, the pneumococcal capsule swells sharply).
Specific prophylaxis pneumococcal disease is carried out using vaccines prepared from highly purified capsular polysaccharides of those 12-14 serovariants that most often cause disease (1, 2, 3, 4, 6A, 7, 8, 9, 12, 14, 18C, 19, 25) . Vaccines are highly immunogenic.
MICROBIOLOGY OF SCARLET FINA
Scarlet fever(Late Late . scarlatium- bright red color) - an acute infectious disease that is clinically manifested by tonsillitis, lymphadenitis, small-pointed bright red rash on the skin and mucous membranes, followed by peeling, as well as general intoxication of the body and a tendency to purulent-septic and allergic complications.
The causative agents of scarlet fever are group A beta-hemolytic streptococci, which have the M-antigen and produce erythrogenin. The etiological role in scarlet fever was attributed to various microorganisms - protozoa, anaerobic and other cocci, streptococci, filterable forms of streptococcus, viruses. The decisive contribution to the elucidation of the true cause of scarlet fever was made by Russian scientists G. N. Gabrichevsky, I. G. Savchenko and the American scientists G. F. Dick and G. H. Dick. I. G. Savchenko back in 1905 - 1906. showed that scarlatinal streptococcus produces a toxin, and the antitoxic serum obtained by it has a good therapeutic effect. Based on the works of I. G. Savchenko, the Dick spouses in 1923 - 1924. showed that:
1) intradermal administration of a small dose of toxin to persons who have not suffered from scarlet fever causes a positive local toxic reaction in the form of redness and swelling (Dick's reaction);
2) in persons who have had scarlet fever, this reaction is negative (the toxin is neutralized by the antitoxin they have);
3) the introduction of large doses of the toxin subcutaneously to persons who have not suffered from scarlet fever causes them symptoms characteristic of scarlet fever.
Finally, by infecting volunteers with a culture of streptococcus, they were able to reproduce scarlet fever. Currently, the streptococcal etiology of scarlet fever is generally recognized. The peculiarity here lies in the fact that scarlet fever is caused not by any one serotype of streptococci, but by any of the beta-hemolytic streptococci that has the M-antigen and produces erythrogenin. However, in the epidemiology of scarlet fever in different countries, in different regions and at different times, the main role is played by streptococci that have different M-antigen serotypes (1, 2, 4 or another) and produce erythrogenins of different serotypes (A, B, C). It is possible to change these serotypes.
The main factors of pathogenicity of streptococci in scarlet fever are exotoxin (erythrogenin), pyogenic-septic and allergenic properties of streptococcus and its erythrogenin. Erythrogenin consists of two components - a thermolabile protein (actually a toxin) and a thermostable substance with allergenic properties.
Infection with scarlet fever occurs mainly by airborne droplets, however, any wound surfaces can be the entrance gate. The incubation period is 3 - 7, sometimes 11 days. In the pathogenesis of scarlet fever, 3 main points associated with the properties of the pathogen are reflected:
1) the action of scarlatinal toxin, which causes the development of toxicosis - the first period of the disease. It is characterized by damage to peripheral blood vessels, the appearance of a small-pointed rash of bright red color, as well as fever and general intoxication. The development of immunity is associated with the appearance and accumulation of antitoxin in the blood;
2) the action of the streptococcus itself. It is nonspecific and manifests itself in the development of various purulent-septic processes (otitis, lymphadenitis, nephritis appear on the 2nd - 3rd week of the disease);
3) sensitization of the organism. It is reflected in the form of various complications such as nephronephritis, polyarthritis, cardiovascular diseases, etc. on the 2nd - 3rd week. illness.
In the clinic of scarlet fever, stage I (toxicosis) and stage II are also distinguished, when purulent-inflammatory and allergic complications are observed. In connection with the use of antibiotics (penicillin) for the treatment of scarlet fever, the frequency and severity of complications have decreased significantly.
Post-infectious immunity strong, long-term (repeated diseases are observed in 2-16% of cases), due to antitoxins and immune memory cells. In those who have been ill, the allergic state to the scarlatinal allergen also persists. It is detected by intradermal injection of killed streptococci. In patients who have been ill at the injection site - redness, swelling, soreness (Aristovsky-Fanconi test). To test for the presence of antitoxic immunity in children, the Dick reaction is used. With its help, it was established that passive immunity in children of the 1st year of life is preserved during the first 3-4 months.
Laboratory diagnostics. In typical cases, the clinical picture of scarlet fever is so clear that bacteriological diagnosis is not carried out. In other cases, it consists in isolating a pure culture of beta-hemolytic streptococcus, which in all patients with scarlet fever is found on the mucous membrane of the pharynx. Aerobic gram-positive cocci assigned to genera Aerococcus, Leuconostoc, Pediococcus and Lactococcus are characterized by low pathogenicity. The diseases they cause in humans are rare and predominantly in people with impaired immune systems.
Page 39 of 91
Morphological and tinctorial properties. Streptococci - Streptococcus (first described by Ogston in 1881) have the appearance of cocci located in chains. The length of the chains is very variable. In pathological material and on dense nutrient media, they are short of 4-6 individual cocci; on liquid nutrient media, unusually long chains are found, which include many tens of individual cocci (see Fig. 60) - sometimes the chains consist of paired cocci that have slightly elongated shape (diplostreptococci). The diameter of individual individuals varies between 0.5-1 microns. They do not form spores or capsules, they do not have flagella. There are such varieties of streptococci that have a capsule in the pathological material. Streptococci stain well with aniline dyes and are Gram-positive.
Cultural and biochemical properties. Streptococci are a large group of bacteria that includes many varieties that differ from each other in cultural, biological and pathogenic properties. Streptococci grow in aerobic conditions or as facultative anaerobes. On simple nutrient media, they either do not develop at all, or grow extremely poorly, especially pathogenic species.
Rice. 64. Streptococcus colonies on sugar agar.
For the cultivation of streptococci, nutrient media are used, adding 1% glucose, 5-10% blood, 10-20% serum or ascitic fluid to them. The reaction of the medium is slightly alkaline (pH 7.2-7.6). The optimum temperature is 37°.
After 24 hours of growth, small grayish-white, slightly hazy colonies develop on the agar. Under a microscope at low magnification, they have a granular appearance. Larger colonies on blood agar. In some strains, they are surrounded by a light zone of hemolysis (Fig. 64). In others, a green color appears around the colony, and finally, in others, no changes are observed.
On the broth, streptococci grow in the form of a characteristic near-bottom, parietal, finely crumbly sediment, leaving the medium transparent. Some streptococci give diffuse growth.
Streptococci can decompose lactose, glucose, sucrose and sometimes mannitol with the formation of acids (without gas). Some streptococci have a reducing ability.
resistance. Streptococci show considerable resistance to physical and chemical influences. In the dried state, especially surrounded by a protein coat, they remain viable at room temperature for several months. When heated in a humid environment to 70 °, some species die no earlier than an hour later. Disinfectants kill streptococci in the following terms: 1-5% phenol solution - within 15-20 minutes, depending on the concentration of the drug, 0.5% Lysol solution - within 15 minutes. Under the action of rivanol at a dilution of 1: 100,000 and vucine at a dilution of 1: 80,000, streptococci die.
Toxin formation and pathogenicity for animals. The picture of the disease in streptococcal infections leaves no doubt that streptococci act on the human body through the toxic products they secrete. On liquid nutrient media, streptococci secrete exotoxin-type poisons found in culture filtrates. Exotoxins include 1) hemotoxin (streptolysin O and streptolysin S), which dissolves red blood cells. This poison exerts its effect both in vivo and in vitro; 2) erythrogenic toxin (erythrogenin), which is a specific scarlet fever toxin. With the introduction of this toxin intradermally, a vascular reaction in the form of redness appears in persons sensitive to scarlet fever. This toxin consists of two fractions. Fraction A is thermolabile, has antigenic properties and is neutralized by antitoxic anti-scarlet fever serum. Fraction B is thermostable and is an allergen - 3) leukocidin, which destroys leukocytes and 4) necrotoxin, which causes tissue necrosis. Enzymes include fibrinolysin (streptokinase) and hyaluronidase.
Along with exotoxins, toxic substances such as endotoxin were found in streptococci. Of laboratory animals, rabbits are most sensitive to streptococci, and to a lesser extent guinea pigs and white mice.
Depending on the virulence of the cultures, streptococci may cause local inflammation or sepsis in a susceptible animal.
Determination of fibrinolysin (streptokinase). To 10 ml of human blood add 1 ml of 2% sodium citrate solution. After settling, unstained plasma is separated, 
Rice. 65. Hemolytic streptococcus. Growth on blood agar.
diluted with sterile saline 1:3 and add 0.5 ml of 18-20-hour broth culture of the test streptococcus. The tubes are gently shaken and placed in a water bath at 42° for 20-30 minutes. At this time, a fibrin clot is formed. The test tubes are left for 20 minutes in a water bath; in the presence of fibrinolysin, the clot dissolves within 20 minutes. Some strains of streptococci dissolve fibrin very slowly, therefore, 2 hours after standing in a water bath, the test tubes are transferred to a thermostat and the result of the experiment is taken into account the next day.
Streptococcus classification. Initially, streptococci were classified according to the length of the chains (Streptococcus longus, Streptococcus brevis). Such a division turned out to be untenable, since this sign is very unstable.
More rational is the classification of Schottmuller, which is based on the ratio of streptococci to erythrocytes. Depending on the nature of growth on blood agar, the following types of streptococci are distinguished:
- hemolytic streptococcus - Streptococcus haemolyticus dissolves red blood cells (Fig. 65);
- greenish streptococcus - Streptococcus viridans forms greenish-gray colonies on blood agar, which are surrounded by opaque areas of olive-greenish color;
- non-hemolytic streptococcus - Streptococcus anhaemolyticus on blood agar does not cause any changes.
Rice. 63. Staphylococcus in pus. Gram stain.
Rice. 66. Streptococcus in pus. Gram stain.
The liquid material is applied to a glass slide with a loop or a Pasteur pipette. If the material is thick, it is rubbed on the glass in a drop of saline. The material from the swab is applied to a sterilized glass slide.
When gram-positive cocci located in chains are detected under a microscope, the streptococcal etiology of the disease is tentatively established.
The material should then be plated on sugar and blood agar plates to obtain isolated colonies and isolate a pure culture. Small (0.5 mm), flat, dryish, grayish, transparent colonies of streptococcus make it possible to differentiate the type of streptococcus (hemolytic, green, non-hemolytic).
To determine the reducing ability of streptococci, 0.1 ml of an 18-hour test broth culture is inoculated into 5 ml of milk with methylene blue (the medium consists of sterile skim milk, to which a 1% aqueous solution of methylene blue is added in an amount of 2 ml per 100 ml of milk) and put in a thermostat at 37 ° for 24 hours. With a positive reaction, the milk becomes colorless, with a negative reaction, the color of the medium does not change.
To determine the virulence and toxigenicity of streptococci, a rabbit is injected intradermally with 200-400 million microbial bodies. After 24-48 hours, an inflammatory reaction of varying degrees appears at the injection site, with or without necrosis.
Identification of hemolytic streptococci is also carried out using the agglutination and precipitation reaction.
Agglutination reaction. One drop of saline and a drop of agglutinating group sera A, B, C, D (whole or diluted with saline 1:2 or 1:10) are applied to the glass slide with separate Pasteur pipettes, into which the broth culture under study is added drop by drop. If the culture is not very granular and does not give spontaneous agglutination, then within half an hour it is possible to determine the group of streptococcus. In addition to the group, it is possible to determine the type of streptococcus within group A. Typing is also carried out using the agglutination test on glass with type-specific sera and according to the same method as the group determination.
Specific prevention and therapy. Vaccination and vaccine therapy are not widely used in streptococcal diseases. More often use polyvalent antistreptococcal serum. Sulfanilamide preparations are distinguished by high activity in the treatment of streptococcal diseases. These drugs, both when taken orally and when applied topically or parenterally, have a sharply inhibitory effect on streptococci. For the treatment of streptococcal infections, antibiotics - penicillin, tetracycline, etc. - are used with great success.