Streptococcus mitis- An Overview


Streptococcus mitis is a type of bacteria that is part of the normal flora of the human body, especially in the oropharynx, skin, and gastrointestinal tract . It is a Gram-positive coccus that is arranged in chains or pairs . It can cause infections such as endocarditis, bacteremia, and septicemia if it escapes from its niche or in immunocompromised patients . It may also be associated with colon adenocarcinoma.

The genus name `mitis` has been derived from the Latin term `mitis` meaning mild, indicating that it is an organism with low pathogenicity and virulence that is involved in different types of mild infections. It was first isolated and discovered by Andrewes and Horder in 1906 from the human oropharynx region. S. mitis is the primary species of the mitis group consisting of twelve other species including the highly pathogenic S. pneumoniae. The species are put under the mitis group of Streptococci on the basis of their 16S rRNA gene sequences and nucleic acid hybridization data.

S. mitis is a mesophilic alpha-hemolytic species of Streptococcus that inhabits the oral cavity. It is a coccus (spherical shaped), gram-positive, catalase negative, and facultative anaerobe. It was previously classified as Streptococcus mitior. Streptococcus mitis is known to cause several medical conditions one of them being infective endocarditis.

S. mitis is competent for natural genetic transformation, which means that it can take up exogenous DNA and incorporate it into its genome by homologous recombination. This allows it to acquire new genes and traits from other bacteria, such as antibiotic resistance or virulence factors. S. mitis can also employ a predatory fratricidal mechanism for active acquisition of homologous DNA, where it kills other bacteria and uses their DNA as a source of genetic material.

S. mitis has been reported to survive for over two years on the Surveyor 3 probe on the Moon, but this is most likely due to contamination upon return to Earth. The Apollo 12 crew received pieces of Surveyor in 1969, one of these was the TV camera. The probe was then analyzed to consider how the lunar environment affected the material. S. mitis was found inside a piece of foam located inside the camera, but it was probably introduced during handling or storage after landing.