Streptococci are immobile and do not form permanent forms (spores) (see also Streptococci/Microbiology). They belong to the normal flora of skin and mucosa. They only lead to disease when the immune system is weakened.
Streptococci are approx. 0.5 to 1.0 µm in size and are part of the normal human flora. As germs, streptococci can also cause severe diseases. Greening streptococci are part of the normal flora in the oral cavity. Several of them can cause valvular heart disease when they cross over into the blood. One of these is Streptococcus mutans, which plays an important role in the development of caries.
Other streptococci can cause serious infections such as tonsillitis , otitis media , scarlet fever , wound infections , meningitis , endocarditis , sepsis or are involved in the development of dental caries. Non pathogenic streptococci are used in the production of yogurt, cottage cheese, sour cream, kefir and cheese and in the agriculture of fermented feed.
Streptococci can be distinguished according to their haemolysis capacity, that is, their ability to dissolve red blood cells (erythrocytes) by destroying their cell membrane. There are several types of streptococci:
- Streptococcus agalactiae
- Streptococcus avium
- Streptococcus anginosus
- Streptococcus bovis
- Streptococcus durans
- Streptococcus mutans
- Streptococcus pneumoniae
- Streptococcus pyogenes
- Streptococcus viridans