TANT TO /3-LACTAM ANTIBIOTICS

WHEN the antibiotic resistance patterns of ten clinical isolates of Bacteroides fragilis were determined it was noted that one strain was exceptionally resistant to /3-lactam antibiotics. This highly resistant strain produced a /3-lactamase, which was absent from the other moderately resistant strains. It was therefore investigated further because there has been no detailed study of /3-lactamases from Bacteroides spp. Bacteriodes fragilis and related species form the predominant flora of the human large intestine (Drasar, Shiner and McLeod, 1969). They are usually opportunist pathogens, and infection frequently occurs by autoinfection from the gastro-intestinal tract (Marcoux et al., 1970; Felner and Dowell, 1971) or from the female genital tract (Gelb and Seligrnan, 1970; Ledger, Sweet and Headington, 1971). B. fragilis is moderately or very resistant to many of the common antibiotics (Bodner, Koenig and Goodman, 1970; Kislak, 1972). This organism also provides a large reservoir of antibiotic-resistant organisms in the body and might constitute a source of resistance for other organisms i