Isolation, characterization and ecological distribution of recently recognized propionic acid-negative Bacteroides species from human sources.

140 strains of anaerobic, Gram-negative, propionate-negative, non-pigmented rods (Bacteroides oralis group) were isolated from normal flora and from clinical specimens. They were characterized by physiological tests, gas chromatography of the acid end products, and determination of the G + C content of their DNA. In addition, their distribution in the various biotopes of the human body (oropharyngeal tract, genitourinary tract, and gut) and in clinical specimens was investigated. The strains could be assigned to the recently described species Bacteroides denticola, B. buccae, B. buccalis, and B. oris, or to B. bivius, B. disiens and B. oralis. In the investigated group, especially B. bivius exhibits an antibiotic resistance--particularly against the beta-lactam antibiotics--comparable to that of B. fragilis.