Cefoxitin-induced antibiotic resistance in Enterobacter species in the community hospital

The aim of this study was to determine whether beta-lactamases could be induced by cefoxitin in the community hospital, since this problem of antibiotic resistance has been shown to exist at the tertiary care level. One hundred sixty-six Enterobacter species isolated from patients in two community hospitals in Dayton, Ohio, were tested for cefoxitin induction of beta-lactamase production by a disk-approximation method. Piperacillin and cefoxitin disks were placed in approximation to each other on Mueller-Hinton plates inoculated with Enterobacter species with appropriate controls. Three Enterobacter strains (1.8%) showed truncation of the zone of inhibition (indicating beta-lactamase induction) with sensitivity to both cefoxitin and piperacillin. However, 84 strains (50.6%) showed truncation around the piperacillin disk with resistance to cefoxitin. One hundred fifty (90.0%) strains showed resistance to cefoxitin. These data indicate that cefoxitin induction of beta-lactamases in Enterobacter species is indeed a potential problem in incurring antibiotic resistance in the community hospital.