Abstract
beta-Lactamase from strains of Bacteroides melaninogenicus and Bacteroides oralis hydrolyzed penicillin more rapidly than ampicillin or carbenicillin. Cephalothin and a chromogenic cephalosporin (87/312) were also hydrolyzed by the enzyme. Activity was found only in beta-lactam-resistant strains, but there was considerable variation in activity among strains having the same minimal inhibitory concentrations of antibiotic. beta-Lactamase activity was cell bound and appeared to be tightly associated with the cell envelope since detergents were required to elute this activity.