Microorganisms surround us everywhere and live in our body, being an integral part of it and the world as a whole. However, not all of them are dangerous to our health, on the contrary, those bacteria that make up the normal microflora of various human organs, resist alien microbes and prevent the occurrence of infections. In addition, the immune system is an important defense component, but even weakened pathogenic flora can cause disease if it is weakened. One of their prominent representatives is streptococcus viridans, which will be discussed.
Basic information
Otherwise referred to as “green streptococcus”, it is a normal inhabitant of the human oral cavity, where it is localized on the teeth and gums and often causes tooth decay. This is because the structure of streptococcus viridans has a special surface protein that is able to bind saliva and thus attach to the tooth. And when sugar comes in with food, it turns it into lactic acid, which corrodes enamel. It got its interesting name because when it is bacteriologically sown on the nutrient medium of blood agar, these bacteria form a green hemolysis zone around their colony. However, there are other groups of them, these are hemolytic streptococci (completely hemolysing the environment) and non-hemolytic (do not have hemolytic enzymes). Compared with the first streptococcus group viridans are not so dangerous for the human body and are much less virulent. However, when immunity is weakened, they actively multiply and exert a pathogenic effect, causing opportunistic infections, and not always of a mild course.
Microbiology
Now let's take a closer look at streptococcus viridans. If we talk about these bacteria from a microbiological point of view, they are spherical or ovoid gram-positive cocci that do not form spores. They belong to the group of facultative anaerobes and are part of the Streptococcaceae family. To find out what streptococcus viridans looks like, what it is, just look in a light microscope. So you can see that most often they are arranged in pairs or assembled in chains, but at the same time remain motionless. Their danger to our immunity lies in the fact that they are able to form a capsule that protects them from phagocytosis by specialized blood cells, and can also easily turn into the L-shape, thus mutating, and therefore can be hidden for a long time from the components of our protective system.
Sowing and virulence
The nutritional needs of these bacteria, unlike staphylococci, are quite complex. They grow well only on those media in the preparation of which whole blood or serum was used, and they also need carbohydrates for nutrition. That is why blood agar is most often used for bacteriological culture of green streptococci. In the external environment they are quite stable, so, for example, on dried biomaterials (blood, pus, sputum), they can remain viable for several months. When pasteurization, disinfection, they die, but not immediately. So, when they are heated to a temperature of 60 degrees Celsius, their death occurs only after half an hour, and when using des. funds - in 15 minutes.
Epidemiology
The fact that streptococcus viridans is the norm, along with many bacteria, is among the usual microflora of the human body. However, this applies only to a certain amount of its strain, and it can be replenished from infected people, that is, carriers of streptococci or already infected with one of the many forms of infection (tonsillitis, scarlet fever, pneumonia, etc.). In this case, the most dangerous patients with damage to the upper respiratory tract, since they secrete much more streptococci into the environment. Hence, the main route of infection is airborne, that is, when talking, sneezing, coughing, kissing, etc .; in some cases, alimentary (with food) and contact (dirty hands) are also possible. So, it is known that many group A streptococci can retain their virulent properties for a long time if they come into contact with products that are, in fact, a favorable environment for them. These include eggs, milk, ham and shellfish.
Complications
The most formidable disease caused by green and non-hemolytic streptococci is infectious endocarditis. The fact is that when injuring the mucous membrane of the oral cavity (gums, tongue) with a toothbrush, floss or stomatitis, streptococcus viridans enter the local and then the systemic circulation. Reaching the heart, they are able to attach to the valves and colonize on them. Thus, this disease develops. It begins, as a rule, with general manifestations: weakness, malaise, and fever. This is primarily due to the fact that more often it is caused by moderately or slightly virulent strains.
Clinic and outcomes
If highly pathogenic bacteria become the cause of infectious endocarditis, then the disease begins acutely and is accompanied by febrile temperature, up to forty degrees. In this case, muscle and joint pains occur simultaneously, and heart murmurs are auscultated. The danger of this disease lies in the destruction of the endocardium, that is, the deformation of the valves with the appearance of bacterial vegetation on them. When they exfoliate, a microbial embolism of the vessels develops, leading to heart attacks and strokes. In addition, large arterial aneurysms, brain abscesses, meningitis, encephalopathy, and heart failure can form .