Bacteriocin typing of streptococcal isolates from endocarditis.

A typing system based on bacteriocin production and sensitivity for Streptococcus sanguis strains was devised. Bacteriocin producer strains were grown (37degrees C) anaerobically on brain heart infusion-yeast extract agar for 18 h. Bacteriocin indicator strains were suspended to molten brain heart infusion-yeast extract agar and then overlayed onto the producer strain. After an additional 18 to 24 h of incubation, zones of bacteriocin inhibition were recorded. After establishment of the typing system, eight Streptococcus strains from bacterial endocarditis patients were characterized by the typing system. Four patient strains had identical bacteriocin reduction patterns but could be differentiated by differences in their bacteriocin sensitivity. Two isolates from the same patient had identical production and sensitivity patterns. By including both bacteriocin production and bacteriocin sensitivity, all seven epidemiologically unrelated isolates could be differentiated. On the basis of these results, there does not appear to be a correlation between bacteriocin production and infectivity, but the usefulness of the application of a typing system to a clinical situation is demonstrated.