Streptococcus. general characteristics
The term Streptococcus is morphological and unites cocci arranged in pairs or chains. The combination of two words – (twisted, concatenated) and "coccos" (berry). So called these microorganisms famous surgeon Theodor Billroth in 1874.
The genus Streptococcus has certain biochemical characteristics. Thus, the cocci of lactic acid is high. At the same time, they differ significantly in cultural properties and pathogenicity. It can cause fatal diseases while under special conditions. Among them are non-pathogenic cocci. In general, there are a number of different body organisms.
Streptococcus may be pathogenic for humans and lower animals. Saprophytes and other everyday products.
A large number of studies devoted to the biology of streptococci. The structure of the individual is a pathway.
Streptococcus. Morphological and cultural properties.
1 micron in diameter) are organized in long and short chains. Long chains have up to 50 or more cells, short – 4-10. Inside chains, cells are often arranged in pairs. Chains are formed when they are in the same plane and remain linked. Streptococcus fixed, gram-positive, non-spore-forming bacteria. This feature is not permanent.
Most streptococci grow in the presence of oxygen, but may not need it. Some species are strict anaerobes. Streptococcus grow well on enriched media. Visible colonies appear after 24-48 hours. Can be obtained by cultivation on the medium with the addition of serum (not heated) or whole blood. Streptococcus can grow in milk. It can also grow at a temperature of 15 ° C to 45 ° C. Most species can be grown in the body. All catalase and oxidase negative.
Well preserved in dry, crumb-up to several months. Crumbled at a temperature of + 60 ° C for 15 minutes. Solutions of phenol, iodine, alcohol are also destructive for streptococcus.
Streptococcus with blood of 5% (blood agar):
1. Alpha-hemolytic (cause incomplete hemolysis) – colonies are surrounded by a greenish zone
1. Alpha-hemolytic streptococci Sinus infection or odontogenic abscesses, but they can also be associated with more severe processes, for example, subacute bacterial endocarditis; 2. Beta-hemolytic streptococci – are more virulent and are associated with an acute inflammatory reaction; 3. Gamma streptococci are non-pathogenic for humans.
Another classification based on biochemical properties divides streptococci into groups:
1. Group A – pyogenic (pyogenic) β-hemolytic streptococci – it is a disease that affects the sepsis, rheumatism and glomerulonephritis.
2. group B – green streptococci. Do not produce hemolysins, do not cause hemolysis on blood agar. It has been shown that it has been shown that it has been found in the United States of America. They are also widespread in nature.
3. Group B – Enterococci (
4. Group G – dairy streptococci. Rarely cause disease. Usually present in milk and determine the natural "souring" of milk.
5. Group D – peptostreptokokki. The abdominal cavity, the pelvis and the lungs. Occur among the normal microflora of the large intestine and oral cavity.
There is another classification of the cell wall polysaccharide. It was proposed in 1920 by Landsfield (Lancefield). The so-called C-carbohydrate of the streptococcus polysaccharide has been defined as determined in the precipitation reaction. Landsfield identified 13 groups: A, B, C, D, E, F, G, H, K, L, M, O, S.
In 90% of cases, human streptococci of group A (β-hemolytic streptococci), which include Str. pyogenes (pyogenic streptococcus). Streptococcus This is the main virulence factor of the phagocytes. The cell wall (villous layer). It is divided into more than 60 serovars.
Toxic properties produced by β-hemolytic streptococcus group A
Streptococcus produce many extracellular substances, including enzymes and toxins. Among them: hemolysins, leukocidins, streptokinase, streptodornaz, hyaluronidase, erythrogenic toxin.
Streptolysins. Streptococcus constitutes the leukocidin and hemolysin. Streptolysin S group of A. A. Streptolysin O – group A and some other groups.
Forms of both hemolysins. It is therefore recommended that it be treated with water, where it is anaerobic. In contrast, streptolysin S and he therefore does not cause superficial hemolysis. Since it has been found that it has been immunologically active, it has been shown that it has been recognized as the pathogen.
The titer of antistreptolysin O (ASO) in serum of more than 160-200 U is considered pathologically high. This indicates either a recent streptococcal infection or chronic process.
Streptokinase (fibrinolysin) is an activator of cleansing and other proteins. Blood clotting plays the limits of spread of local infection. It is a condition that leads to the generalized forms.
Streptodornase (streptococcal deoxyribonuclease, DNase) dilutes the thick, viscous exudate formed during pneumonia. The enzyme activity is associated with deoxyribonucleoprotein – a factor responsible for viscosity.
Hyaluronidase (proliferation factor, invasion). It is increased.
Erythrogenic toxin. Causes a rash that occurs with scarlet fever. Scarlet fever can be caused only by strains that produce an erythrogenic toxin. Erythrogenic toxin is produced by lysogenic streptococci. If the strain is a phage genome, the ability to produce a toxin is lost. Non-toxigenic streptococci after lysogenic conversion will not produce an erythrogenic toxin.
Erythrogenic toxin has an antigenic activity, causing humans to neutralize the toxin. People who have erythrogenic toxin (antitoxins) do not develop a rash, although they remain susceptible to streptococcal infection.
Streptococcus. Pathogenesis and clinic of infection
Typical pathological damage caused by hemolytic streptococcus is a common cellulitis. The fluid contains a small amount of fibrin. Toxic products secreted by microbes help streptococci to overcome both intact tissue and inflammatory barriers. Region of the affected side. Most well-known forms of streptococcal infection is a manifestation of cellulite. It is a cellulite of the pharynx. It is a cell of the pharynx.
Immunological reactions of the body usually follow a streptococcal infection (most commonly, a sore throat). For example, it was caused by group A streptococci; A form of kidney disease (glomerulonephritis) follows the respiratory tract or skin. Many different pathological processes are associated with streptococcal infections.
Diseases caused by the invasion of β-hemolytic streptococcus group A (Str. pyogenes)
The path to the area of lymphatic pathways takes place. The pathogen can enter the bloodstream, which leads to the development of bacteremia.
Phlegmon. Entrance of the infection. Cellulitis is a deeply developing disease, accompanied by inflammation and redness, swelling and soreness. The lymphatic system is quickly involved in the process. The lymphatic ducts are inflamed and visible. The nose of the wings and the nasolabial folds of the skin are more affected. Other skin areas may be affected.
Postpartum fever (puerperal sepsis). Entrance gate – endometrium. If, after the childbirth, it penetrates into the patch (5-hemolytic streptococcus of group A, postpartum fever is undressed, which is, essentially, septicemia wound-endometrium.
Wound infection. Infection of traumatic wounds with β-hemolytic streptococcus group A.
The processes can be carried out in streptococcal sepsis.
Diseases associated with local infection with β-hemolytic streptococcus group A
Streptococcal sore throat. The most frequent manifestation of streptococcal infection. It is attached to the epithelium of the larynx.
There is a tendency for the disease to occur in infants and young women. Cervical lymph nodes are usually enlarged. The disease can last for several weeks.
It has been shown that it has a lot of nasopharyngitis;
If the streptococcus infectious strains produce an erythrogenic toxin, a scarlet rash appears. It has no effect on streptococcal infection.
Streptococcal nasopharyngitis usually does not spread to the lungs. Pneumonia is caused by β-hemolytic streptococcus is often the result of viral infections, such as influenza or measles, which appear to significantly increase susceptibility to infection.
Streptoderma (pyoderma streptococcal, impetigo contagiosa) – highly contagious skin lesion. The disease is more common in children, often by streptococcus and staphylococcus.
Sensitive skin of young children. streptococci occupy, usually not penetrating into its inner layers. If invasion into the skin occurs, a disease called impetigo develops. It has a very distinctive picture. Initially, small bubbles are formed, filled with liquid. They are covered with reddish on the periphery. There may be up to 20 such elements. When joining staphylococcus elements suppurate. Impetigo contagiosa in children is often complicated by the development of glomerulonephritis.
During bacteremia, streptococci can be settled on normal or previously damaged heart valves. The most dangerous is caused by β-hemolytic streptococcus group A, accompanied by rapid destruction of valves.
After extraction of teeth
30% of patients develop bacteremia caused by verdant streptococcus, an ordinary inhabitant of the upper respiratory tract. If this is the case, it can cause so-called subacute bacterial endocarditis.
Streptococcus. Complication of infection (rheumatism, glomerulonephritis)
After acute infection caused by β – hemolytic streptococcus group A, there is a latent period of 1-4 weeks, after which rheumatism or nephritis sometimes develop. The state of hypersensitivity, and the formation of these conditions.
Nephritis is often preceded by skin lesions, rheumatism – respiratory tract infections.
Glomerulonephritis develops in some patients after 3 weeks. It can begin the glomerular membrane. Acute nephritis, blood and protein appear in the urine, edema, blood pressure rises, nitrogen retention is noted. In most cases, it becomes chronic glomerulonephritis, followed by renal failure.
Rheumatism is caused by the β-hemolytic streptococcus group A. Some streptococci can be expressed as the heart of the human heart. Patients form antibodies to streptococcus, which can act cytotoxicly on heart cells.
The beginning of rheumatism is preceded by an infection, sometimes not recognized, but often – severe streptococcal tonsillitis. The symptoms are fever, malaise, arthritis and signs of inflammation of the endocardium, myocardium and pericardium.
Rheumatism tends to exacerbate. Heart disease progresses with repeated attacks.
Streptococcus. Immunity to infection
Resistance to β-hemolytic streptococcus is type-specific. It is a person who has been able to recover the disease.
The development of resistance is associated with type-specific streptococcus M-protein. Protein secreted by phagocytosis.
Immunity against erythrogenic toxin is due to the presence of antitoxin in the blood. It prevents the development of a rash with scarlet infection, but does not protect against streptococcal infection.
Antibodies to streptolysin O (antistreptolysins) show immunity. Highly antistreptoadzin titers (more than 250 U), indicate that there has been more patients in patients with rheumatism than in patients with streptococcal infections.
Streptococcus. Antibiotic Sensitivity
Strains of β-hemolytic streptococcus are sensitive to penicillin and, in most cases, to erythromycin. The use of bacteriostatic (bactericidal or bacteriostatic) is extremely important. For acute respiratory infections (angina), should not be less than 10 days. It is possible to use drugs of streptococcus.
Streptococcus. Sources of infection. The transmission mechanism. Preventive measures
Many streptococci (green, enterococci, etc.) are the microflora of the human body. Where they should not be (for example, on heart valves). It is advisable to prevent heart disease.
β-hemolytic streptococcus is a pathogenic microbe. It can be a clinically severe or subclinical infection or carrier state. It is possible to pass through the skin through the skin. Heyou is in the midst of her death. A minute touch is enough to cause a dangerous streptococcal infection in patients or staff.
Thus, β-hemolytic streptococcus from the nasal or oral mucosa, or patients with various forms of streptococcal infection.
The control measures relate primarily to the beta-hemolytic streptococci of the group of animals.
These measures include:
Identification of patients (including penicillin, erythromycin and other antibiotics, active against gram-positive microorganisms).
It is recommended to take care of all the hospitals and surgical hospitals. Very difficult procedure, not always successful. Sometimes there is a high risk area for patients.
Streptococcus. Laboratory diagnosis of infection
For a diagnosis of acute streptococcal infections (with the exception of scarlet fever with clinically significant symptoms), bacteriological and serological studies are necessary.
In septic conditions, blood is sown; in case of purulent lesions, a detachable wound is sown, ulcers, sowing of mucous membranes. It has been found that it is the first time that it has been cleaned. In all cases, it is most convenient to use a cotton swab. The swab is placed in a laboratory, where it is known as a nutrient containing blood or serum. When sowing, do not rubbing it into the agar.
The highest percentage of the seeding can be obtained at 2-3 times. The material is incubated for 3-4 hours at 37 ° C and sown on a blood agar plate.
Sowing blood is produced in a liquid medium, followed by seeding on blood agar. Blood cultures should not be kept for a long time (up to 2 months) in a thermostat,
The next day, exploring grown colonies. For example, hemolysis or a greenish are selected. Prepare smears, paint them Gram. Positive cocci are under the microscope, which are located in short chains. The colony material is still subject to microscopic examination and subcultured on canted whey or ascitic agar.
Sowing meat-peptone agar, milk and methylene blue, and bile broth.
β-hemolytic streptococcus group doesn’t reduce methylene blue in milk. Enterococcus grows well in simple bile environments.
The biochemical properties of streptococci are determined by the plating on the media, but they are not sufficiently constant. It is advisable to study the biochemical properties of streptococci in the absence of their group C-antigen.
It is carried out using the assay (A, B, C, D) and the hydrochloric acid antigen. Precipitation tubes contribute