Taxonomy
Family: Streptococcaceae

Streptococcus mitis group / Lancefield Group F
- S. mitis
- S. cristatus
- S. oralis
- S. peroris

- S. pneumoniae

Natural habitats
Commensals of the oral cavity, the gastrointestinal tract, and the female genital tract.

Clinical significance
Isolation of these species from blood cultures in asymptomatic patients often does not require antibiotic treatment, if it is due to a transient bacteremia.

They can also be found as transient microbiota of the normal skin and often represent contaminants when isolated from blood cultures.

At the same time these species are the most frequently isolated bacteria in bacterial endocarditis in native valve and less frequently, in prosthetic valve infections.

Careful evaluation of the clinical situation is therefore crucial to correctly interpret the clinical significance of blood culture isolates from the S. mitis- or S. sanguinis group.

In neutropenic patients, streptococcal species from these groups are often responsible for life-threatening sepsis an pneumonia cases following immunosuppression by chemotherapy.