Subacute bacterial endocarditis due to Streptococcus mutans.

A case of subacute bacterial endocarditis due to Streptococcus mutans is presented. The case was successfully treated by intravenous and oral penicillin. Streptococcus mutans is a member of the viridans streptococcal group with properties similar to enterococcal streptococci. Since the enterococci are resistant to penicillin, and isolates of Streptococcus mutans are usually sensitive to penicillin, it is important that medical technologists and microbiologists accurately identify these organisms. The combination of the following characteristics: 1) lack of Group D antigen, 2) acid formation in mannitol broth, 3) failure to hydrolyze hippurate, and 4) formation in five per cent sucrose broth of gelatinous adherent deposits on walls and bottom of tube, distinguish Streptococcus mutans from enterococcal streptococci.