Bacteriologic and clinical study of Bacteroides oris and Bacteroides buccae.

We characterized clinical isolates previously identified in our laboratory as Bacteroides ruminicola, the human strains of which are now classified as Bacteroides oris and Bacteroides buccae. A total of 72 isolates (55 B. buccae isolates and 17 B. oris isolates) recovered over a 10-year period were studied. They were differentiated from each other by special-potency antibiotic disks and the RapID-ANA system. The two organisms were associated with a variety of infections, the majority being pleuropulmonary (29.2%) and infections of the head and neck region (27.8%). The infections were always polymicrobial, usually with more than five organisms per specimen. A total of 44% of the B. oris strains and 27% of the B. buccae strains were resistant to penicillin G (breakpoint, 2 U/ml), and this correlated with the presence of beta-lactamase. Although B. oris and B. buccae are found with some frequency in human infections, they are present primarily as components of a mixed flora.