[Microbiological and clinical studies of infective endocarditis due to nutritionally variant streptococci].

We report four cases of infective endocarditis due to nutritionally variant streptococci (NVS) that occurred between 1981 and 1991. Three female and one male patients had underlying heart diseases. Causative organisms showed satellitism to staphylococci. Two strains were identified as S. adjacens and the other two were identified as S. defectivus by DNA-DNA hybridization. All strains had tolerance and one strain had resistance to benzylpenicillin (MIC 4 micrograms/ml). This penicillin-resistant strain also had tolerance to gentamicin. There was no synergism of benzylpenicillin and gentamicin against this strain by a killing curve in vitro. A 11-year-old female patient with infective endocarditis due to this strain, who had a transposition of great arteries, had large vegetations in external conduits by the Rastelli's operation. Some intensive antimicrobial chemotherapies were unsuccessful and a surgical replacement of the conduits must be done in this case. Since infective endocarditis due to NVS is not rare in Japan, NVS should be considered for the causative organisms in culture negative endocarditis.