Streptococcus bovis- An Overview


Streptococcus bovis (S. bovis) is a Gram-positive bacterium that belongs to the bovis/equinus complex of the viridans Streptococci. It is present in the gastrointestinal tract of humans as a normal inhabitant, along with other Streptococcus species. However, it is present in much fewer numbers than other such species.

S. bovis was first isolated from the gastrointestinal tract of cattle or ruminants by Andrewes and Horder in 1906. The species name `bovis` is taken from the Latin word `bovis` which means cow, bull, or ox, indicating the primary host of the species. It belongs to the Group D of the Lancefield antigen grouping and is considered one of the crucial etiologic agent in different Group D Streptococcus infections.

Previously S. equinus and S. bovis were considered as two separate species, but recent studies involving DNA–DNA hybridization have led to the recognition that the names Streptococcus equinus and Streptococcus bovis are subjective synonyms with the specific epithet Streptococcus equinus having priority. However, so far, this has not been adopted in clinical microbiology and the name ‘S. bovis‘ remains widely used.

Despite being a commensal of the gastrointestinal tract in humans and other animals, S. bovis has been associated with numerous diseases, the most important being colorectal cancer. The species is one of the older members of the bovis group which has now been changed to bovis/ equinus complex because of the genetic similarity of the two species.

S. bovis is a facultative anaerobe that can grow in both aerobic and anaerobic conditions. It is catalase-negative and produces lactic acid as the sole or major end product during carbon metabolism. It exhibits various types of hemolysis on blood agar, but mostly α-hemolysis that produces a green-colored zone around the colonies.

S. bovis can cause different forms of infections in humans, such as bacteremia, endocarditis, sepsis, urinary tract infections, and osteomyelitis . There is also a strong association between infection due to S. bovis and colonic neoplasm (as well as other lesions of the gastrointestinal tract). The exact mechanism of pathogenesis and virulence of S. bovis is not yet clearly understood, but it has been suggested that biofilm formation, adhesins, soluble cell-wall antigens, and coagulation factors are involved in the process .

The diagnosis of S. bovis infection is based on the isolation and identification of the organism from clinical specimens, such as blood or urine. Different cultural, biochemical, and molecular methods can be used for this purpose. The treatment of S. bovis infection usually involves antibiotics such as penicillin or ceftriaxone for four weeks or more depending on the severity and site of infection. In some cases, surgery may be required to remove infected valves or devices. In addition, screening for colorectal cancer is recommended for patients with S. bovis infection as a preventive measure.