Diseases caused by streptococci have attracted the attention of doctors, microbiologists, scientists of other specialties for a long time. There is nothing surprising in this - dangerous strains of these types of bacteria can cause severe inflammatory reactions, and infection in some cases leads to death. In order to fight against diseases more successfully, it is necessary to study the pathogen in detail, evaluate the features of its vital functions and identify what is currently effective against it, which drugs do not provoke the development of resistance in pathological forms.
general information
In microbiology, streptococci are usually called life forms whose diameter varies between 0.8-1 microns. They have the shape of a ball or oval. Bacteria are motionless and form chains, whose length varies significantly. Based on the analysis of staining, streptococci are classified as gram-positive bacteria. Some species form a capsule. The size of the chains is governed by external factors. The more nutritious the liquid medium, the longer the formation will be, while in the dense structure of the chain short beams appear.
Studying the growth of streptococci, scientists have established: shortly before division, bacteria become ovoid. The process of reproduction relative to the plane of the chain is perpendicular. One bacterium is split into pairs.
Cultural qualities
If you grow a life form on agar with the inclusion of blood elements, translucent sticks are generated, the diameter of which does not exceed a couple of millimeters. Studies aimed at identifying the characteristics of the activity of streptococci in the body made it possible to establish: on agar with blood inclusions, bacterial colonies are colorless or stained grayish, easily removed by a loop. Hemolysis for species in the dimensions of the zone differs quite significantly - in some, the diameter is slightly larger than the size of the colony, in others it exceeds quite significantly.
Streptococci assigned to category A in microbiology are able to generate a hemolytic zone, painted in a green tint or a brownish greenish color. The zone may be transparent, sometimes cloudy, and the color intensity and size vary. A colony can also turn green. If the nutrient medium is liquid, more often the colony grows at the bottom, gradually rising along the walls. If you shake the substance, a suspension appears in the liquid in the form of flakes, grains. As a rule, agar is used to study the development of streptococci, in which blood cells obtained from rams and rabbits are added. You can add serum. Agar is used semi-liquid or meat-peptone.
Breeding Nuances
The experiments organized in microbiology with streptococci showed: a combined broth medium allows to achieve good colony growth, accompanied by active production of toxins. The most effective use of casein hydrolyzate, yeast extract. Hemolytic life forms process glucose molecules, thus generating various acids, including lactic acid. It is this factor that limits the propagation of colonies in the substrate.
Streptococci belonging to class A in microbiology are able to maintain viability for a long time, being dried, therefore they are found in dust on objects. Such cultures lose virulence. Life forms belonging to this class show pronounced sensitivity to the penicillin series - the medicines belonging to it give a bactericidal effect. Bacteriostatic is observed when using sulfonamide.
History and Observations
Streptococci was first identified in 1874 when studying erysipelas. The author of the research was biologist Billroth. After some time, streptococcus pyogenes attracted the attention of the scientist Pasteur, who dealt with cases of blood poisoning, diseases associated with foci of suppuration. Streptococcus is a numerous genus of bacteria. It consists of various life forms that differ physiologically, biochemistry, environmental characteristics, the level of danger to human masturbation.
All varieties of streptococci (including streptococcus agalactiae) belong to the category of chemorganotrophic microorganisms that require a substrate for growth. Propagation is possible in blood or in a medium rich in sugar. Certain varieties when grown on agar with blood do not change it, which is why they were called non-hemolytic. Further studies of hemoliticity showed significant species variability, which limits the application of this feature for diagnostic purposes.
Important Features
To separate streptococci into groups, the difference in the process of carbohydrate fermentation is analyzed. True, this symptom is not stable enough and clear to be applicable in the diagnosis of diseases provoked by the pathogen. Currently, the features of carbohydrate fermentation of streptococci are still being studied, but this attribute is not used to identify varieties. Microorganisms belong to the aerobic class, cannot generate catalase, which is how they differ from staphylococci.
A study of streptococcus agalactiae and other species revealed several antigens. Given the characteristics of antigens for a particular life form, they make an accurate diagnosis - this helps to differentiate types. Landsfield developed a system of differentiation into 17 serogroups in 1933. The division base is polysaccharide antigens. For their designation, they decided to use Latin letters in accordance with the alphabet.
Specificity of forms
The most widespread variety is streptococcus pyogenes belonging to group A. To divide its representatives into subspecies within this group, the M-antigen is analyzed. Scientists know more than a hundred serotypes of A-serovar. It has been established: some types belonging to this class have cross-reacting antigenic structures, and their antibodies are able to react with renal tissues, myocardium and other elements of the human body. Such antigens can provoke an immunopathological state.
Growth and conditions
Studying the properties of streptococci, the features of their distribution, microbiologists have established: in nature, these bacteria are found abundantly, in a variety of environments. The division into several categories based on the environmental nuances of existence is accepted. The forms belonging to group A are dangerous only for humans, the second group includes not only pathogenic, but also conditionally dangerous forms that can affect both humans and animals. The third class - oral conditionally dangerous species. Some bacteria can cause anthroponotic infection, while others can cause anthroponotic infection.
In the human body, streptococcus bacilli can be detected in the oral cavity, on the skin, in the intestinal tract and upper organs of the respiratory system. Infection usually occurs by contact with a carrier of the pathogen, with a sick person, or when interacting with recovalescent. Distribution often occurs by airborne droplets, somewhat less often - through direct contact. In the outside world, the bacterium can survive for several days, but heating to 50 degrees leads to the death of microflora within half an hour, sometimes faster.
Status Update
Exploring cases of infection with pyogenic streptococci, microbiologists have proposed several effective options for making an accurate diagnosis. For research, samples of organic fluids are obtained from a sick individual. Use urine, purulent discharge, mucous membranes obtained from the nasal cavity, pharynx. Tissues are sent for bacterioscopic analysis, smears are prepared, stained in accordance with the Gram theory. Sowing involves the use of a Petri dish. In laboratory conditions, they resort to agar with blood inclusions.
As the colony grows, they analyze whether beta-hemolytic streptococcus takes place, or whether other hemolysis features are observed. Then, the isolated culture is finally identified based on the characteristics of the antigen and the specifics of the nuances of the precipitation reaction. For its implementation, precipitinogen is obtained from the culture used in the study. In addition, antisera to different serotypes are used to conduct the test. If blood poisoning is suspected, it is necessary to obtain this liquid from the patient’s body for sowing.
Nuances of analysis
A special rapid test for streptococci is indicated if rheumatism is suspected. The analysis is carried out serological. The doctor’s task is to determine the presence of O-streptolysin antibodies, as well as evaluate the peculiarities of precipitation and identify C-reactive protein structures. The most relevant studies recently practiced are PCR reactions.
What to do?
There are currently no measures to prevent infection with beta-hemolytic streptococci or other varieties of this type of bacteria. The developed vaccines and toxoids have shown their inefficiency, which makes specific prevention impossible at the level of modern technology. At the stage of active development is an anticaries vaccine.
The therapeutic course involves the use of antibacterial compounds. Streptococci can develop resistance to various drugs, including the penicillin series, but this feature is acquired quite slowly. Beta-lactam antibiotics against streptococci are widespread. Benzylpenicillin is actively used. The cephalosporin preparations belonging to the first and second generation show a pronounced effect. You can use macrolides, aminoglycosides.
Diseases and their absence
Streptococci are quite widespread - they can be found on the flora, in the ground, on the skin of representatives of the fauna. Intestinal streptococcus is known and often found. By no means always bacteria of this kind become the cause of serious diseases, and the infections themselves, if they arise, differ significantly in manifestations. Carriage of streptococci in the modern world is extremely widespread, while the carrier is healthy, but can transmit the bacterium of a susceptible individual. First established streptococci, identifying the cause of cow mastitis. Currently, attention to this group of microorganisms has been attracted due to the frequency of occurrence in urogenital human infection. It was possible to establish the presence of varieties of streptococci in the male urethra, the female birth canal. Permanent sexual partners usually reveal the simultaneous carriage of bacteria. It is customary to talk about carriage urethral, ​​pharyngeal. The first involves the presence of bacteria in the urethra, the second - in the oral cavity.
Among other bacterial diseases in the temperate zone, provoked by streptococcus in frequency of occurrence take one of the first places. Hemolytic varieties of these life forms cause diseases not only in humans, but also in various mammals. In healthy people in the digestive tract, the reproductive system, streptococci are present on average in 5-40% of people. Class B is detected in almost every third healthy woman in the vagina. This is one of two main reasons (along with nosocomial infection) that explains the prevalence of streptococcal infections among newborns. Infection usually occurs at the time of birth, infection with bacteria is observed in approximately 75% of cases among children whose mothers were carriers of microflora.
Prevalence features
As can be seen from the studies, most of the carriers of streptococci among people do not even suggest infection. This is due to the absence of symptoms. Bacteria are transmitted by intimate contact. The symptoms that may accompany the infection often do not have specific features, similar to infection with chlamydia, mycoplasma and other pathogenic microorganisms that spread in a similar way. The patient notes dysuria, possible discharge with the inclusion of blood, pus, serous, inflammatory foci appear on the mucous membranes.
Streptococci as a cause of inflammatory processes have been actively considered since 1874, when they were detected in pus in a wound process complicated by infection. In 1906, scientists from different countries proved the importance of streptococcus in the pathogenesis of scarlet fever. Further study of microflora made it possible to understand: streptococcus can initiate rheumatism, however, viruses are probably also involved in the process. Diseases of the throat associated with infection with streptococcus are extremely widespread. By the time the compulsory educational stage is completed, almost every child is ill with tonsillitis or tonsillitis several times due to infection, moreover, the disease can flow without manifesting itself, and in others it is very serious. Indicate throat diseases caused by streptococci, congestion of the tonsils, swelling of the throat tissue and pain when swallowed, trying to speak.
Infection and consequences
Revealed: streptococcal throat infection in some cases leads to the development of rheumatism. On average, complication occurs a couple of weeks after the underlying illness. The first rheumatic attack is characterized by fever, swelling of the joints, pain in this area. In the future there is a risk of chronic heart disease, in which the integrity and functionality of the valves of the organ is impaired. Doctors have not yet been able to establish all the features of the formation of rheumatism. The following assumption is of interest: in the patient’s body there is an allergic response to a certain compound generated by streptococci during life.
If a sore throat is provoked by a rare hemolytic streptococcus, there is a risk of nephritis as a complication of the underlying disease. The inflammatory focus is localized in the kidneys, the organ's ability to work is impaired. Hemolytic streptococcal forms can cause erysipelas. Bacteria penetrate through the integument, the integrity of which is impaired, and then are able to seep into various internal structures and organs. There is a risk of a generalized process, that is, sepsis. Previously, the disease provoked a huge number of deaths, nowadays it is considered treatable if the therapeutic course with antibiotics is started on time. The likelihood of death is still there, but the frequency of occurrence of such cases has significantly decreased.
Infection: the nuances of the process
Streptococcal infection is accompanied by the destruction of red blood cells. In addition to the above, abscesses, phlegmon, boils belong to this class. Osteomyelitis, endocarditis are of a similar nature. Against the background of infection with streptococci, glomerulonephritis can develop. Pneumococcus is considered close in its characteristics to beta-hemolytic streptococcus, which provokes these diseases. This form of streptococcus with a high degree of probability causes pulmonary inflammation, sinusitis.
Streptococcus activity is due to the ability of the microorganism to generate dangerous compounds. Streptolysin, produced by bacteria, negatively affects heart and blood cells. Another poison is erythrogenin, under the influence of which small blood vessels expand, areas of rashes form. The destruction of white blood cells is due to the presence of leukocidin. Certain enzymes generated by the colony simplify its distribution throughout the body and penetration into various tissues.
Infection: immediately noticeable
The area of ​​penetration of streptococcus into the human body manifests itself as an inflammatory reaction. Here a lesion is formed with suppuration, a necrotic zone or a serous reaction. Bacteria generate specific enzymes that allow them to overcome the body's barrier system and leak into the flow of lymph and blood. This leads to the appearance of inflammatory foci in remoteness from the primary area of ​​introduction.
Poisons produced by the colony provoke fever. The patient is vomiting, he is sore and dizzy, there are problems with consciousness, especially pronounced with erysipelas, blood poisoning, and scarlet fever. , . , , . , , , . – .