Comparative stability of meropenem against beta-lactamases from Bacteroides spp.

The activity of meropenem was similar to that of imipenem against 88 clinical isolates of Bacteroides spp., including 28 non-fragilis strains. Four of the isolates were able to hydrolyse cephamycins or penems. Investigation of beta-lactamases from these strains and 10 laboratory stock culture Bacteroides showed that meropenem and imipenem were degraded at a similar rate by cell-free preparations of these enzymes. Some of these strains were able to completely hydrolyse the carbapenems within 2 h. Despite this rapid hydrolysis, MICs of meropenem and imipenem for some of the strains remained within the susceptible range as judged by agar dilution titration.