Susceptibility of cefotetan and Sch 34343 to β-lactamases produced by strains of Bacteroides that hydrolyse cefoxitin or imipenem

Eight strains of the Bacteroides fragilis group that produce unusual beta-lactamases were used to investigate the activity and susceptibility to hydrolysis of cefotetan, a new cephamycin and Sch 34343, a new penem. Cefoxitin and imipenem were also examined for comparison. Antibiotic titrations revealed that cefotetan was less active than cefoxitin against four of the eight strains, and that Sch 34343 was as active or more active than imipenem. Crude enzyme extracts degraded cefotetan more quickly than cefoxitin as judged by high pressure liquid chromatography. Three of the extracts were able to degrade imipenem completely within 1 h and these enzymes degraded Sch 34343 even more rapidly.