Streptococcus viridans: characteristics of the pathogen and infection

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 for our health, on the contrary, those bacteria that make up the normal microflora of various human organs, resist foreign microbes and prevent the occurrence of infections. In addition, an important link in the defense is the immune system, but with its weakening, even a conditionally pathogenic flora can cause disease. One of their brightest representatives is the streptococcus viridans, which will be discussed.

Basic information

Otherwise referred to as "green streptococcus," this is a normal inhabitant of the human mouth, where it is located on the teeth and gums and often becomes the cause of tooth decay. This is because the structure of streptococcus viridans has a special surface protein that is able to bind saliva and thus be attached to the tooth. And when you receive sugar with food, it turns it into lactic acid, corroding enamel. He got his interesting name because when bacteriological planting it on the nutrient medium of blood agar, these bacteria form a greening hemolysis zone around their colony. However, there are other groups, hemolytic streptococci (completely hemolyzing the environment) and nonhemolytic (do not have hemolytic enzymes). In comparison with the first streptococcus group, viridans are not so dangerous to the human body and are much less virulent. However, when immunity is weakened, they actively multiply and exert pathogenic influence, causing opportunistic infections, and not always easy flow.

Microbiology

Now let's look more closely at what is 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 a spore. They belong to the group of facultative anaerobes and include the family Streptococcaceae. To find out what the streptococcus viridans looks like, what it is, just look into the light microscope. So you can see that most often they are located in pairs or are assembled into chains, but they remain motionless. Their danger to our immunity is that they are able to form a capsule that protects them from phagocytosis by specialized blood cells, and can easily turn into L-form, thus mutating, and therefore can for a long time hide from the components of our defense system.

Sowing and virulence

The nutritional needs of these bacteria, in contrast to staphylococci, are quite complex. They grow well only on those environments in the preparation of which whole blood or whey was used, and they also need carbohydrates for nutrition. That is why the most commonly used for bacteriological planting of green streptococci is blood agar. In the external environment, they are quite stable, so, for example, on dried biomaterials (blood, pus, sputum) they can remain viable for several more months. When pasteurized, disinfected, 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 among the habitual microflora of the human body, along with many bacteria, includes and streptococcus viridans - the norm. However, this concerns only 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 numerous forms of infection (tonsillitis, scarlet fever, pneumonia, etc.). In this case, the most dangerous patients with upper respiratory tract infection, as they release much more streptococci into the environment. Hence the main way 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 fall on 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 infective endocarditis. The fact is that when injuring the mucous membrane of the mouth (gums, tongue) with a toothbrush, floss or stomatitis streptococcus viridans get into the local and then the systemic bloodstream. Reaching the heart, they are able to attach to the valves and colonize them. Thus, this disease develops. It begins, as a rule, common manifestations: weakness, malaise, fever. This is primarily due to the fact that it is more often caused by mild- or slightly virulent strains.

Clinic and outcomes

If the cause of infective endocarditis are highly pathogenic bacteria, the disease begins acutely and is accompanied by a febrile temperature, up to forty degrees. At the same time, there are muscular and joint pains in parallel, and heart murmurs are auscultated. The danger of this disease is the destruction of the endocardium, that is, the deformation of the valves with the appearance of bacterial vegetation on them. With their detachment, microbial embolism of the vessels develops, leading to heart attacks and strokes. In addition, aneurysms of large arteries, cerebral abscesses, meningitis, encephalopathy and heart failure can form .