The term streptococci refers to a specific type of bacteria that have certain common microbiological and biochemical properties. These include, for example, that they assume the same color in a certain microbiological staining (the so-called Gram staining) and arrange themselves in the same way under the light microscope. In addition, however, streptococci are extremely diverse and even belong to the most diverse families of bacteria. Depending on the localization and bacterial strain, one streptococcal infection is therefore completely different from the other and must therefore be considered individually.
Causes of streptococcal infection
Streptococci do not necessarily occur as an external infection: Many types of streptococci are naturally present on the mucous membrane of the intestine, vagina, mouth and throat. But even these types of streptococci can cause an infection if they get from the mucous membrane into the bloodstream or if they proliferate too much – relative to the other types of bacteria in the natural skin flora – and take over the number of people. The latter can be the case, for example, if other bacterial species die due to certain circumstances, thus providing more opportunities for reproduction and better conditions for streptococci.
Another risk factor for a streptococcal infection is a weak immune system. Babies as well as older people are therefore particularly at risk of contracting a streptococcal infection. Also people who receive immunosuppressive (i.e. deliberately suppressing the immune system) drugs are statistically more often affected by streptococcal infections.
Diagnosis of a streptococcal infection
If a streptococcal infection is suspected to be the cause of symptoms, a sample of the infected tissue or from the surface can be taken as evidence. Depending on the location of the infection, blood, nerve fluid or urine is taken as sample or a smear is taken. From this material, an attempt can then be made to cultivate the pathogen.
This means that the material is placed in a culture medium that provides all the conditions in which the suspected streptococcus or other bacterial strains can grow well. Later on, the growth can be used to determine which strain it is. It should be noted, however, that this cultivation can be done particularly well from liquid material.
Blood, urine or a smear from the mucous membrane is a good starting material for diagnostic cultivation. Cultivation of skin material, for example, is far less promising. Skin diseases that could have a streptococcal infection as their cause are therefore more likely to be diagnosed by symptoms.
