[Streptococcus bovis, taxonomic status, clinical relevance and antimicrobial susceptibility]

Streptococcus bovis is a large bacterial complex of facultative anaerobic Gram-positive cocci that includes distinct, genetically-related species. Traditionally, S. bovis was classified into three biotypes: I (mannitol fermentation-positive), II/1 (mannitol-negative and β-glucuronidase-negative), and II/2 (mannitol-negative and β-glucuronidase-positive). The introduction of molecular techniques in the last few decades has led to proposals for a genetic classification of this complex: S. bovis biotype I belongs to Streptococcus gallolyticus subsp. gallolyticus, S. bovis biotype II/1 is, in fact, Streptococcus infantarius subsp. infantarius, designated as Streptococcus lutetiensis, and S. bovis biotype II/2 is Streptococcus gallolyticus subsp. pasteurianus, commonly designated as Streptococcus pasteurianus. Although this modern taxonomy is currently accepted, many clinicians remain unfamiliar with these terms. The importance of correct identification lies in the strong association between bacteriemia, endocarditis and/or colon cancer and the various subspecies. In general, S. bovis is more susceptible to antimicrobial agents than other streptococci, but high levels of resistance to macrolides and tetracycline have been described.