Cefotetan: comparative study in vitro against 226 Gram-negative clinical isolates

The activity in vitro of the new cephamycin, cefotetan, was compared with that of cephalothin, cefoxitin, cefuroxime and cefotaxime against 226 recently isolated Gram-negative pathogens (207 Enterobacteriaceae and 19 Acinetobacter). Cefotetan was consistently more potent than cephalothin, cefoxitin and cefuroxime. Cefotaxime and cefotetan were essentially similar in activity against the Enterobacteriaceae with the singular exception of Enterobacter spp. which were markedly more susceptible to the former drug. None of the five agents was especially active against acinetobacter but cefotaxime was the best. Limited tests of bactericidal activity showed that the MBC differed from the MIC by a factor of 4 at most. Increasing the inoculum tested from 10(2) to 10(8) per ml had little adverse effect on the MIC of cefotetan. If the recommendations of the National Committee for Clinical Laboratory Standards for susceptibility to cephalosporins are applicable to cefotetan and the breakpoint criteria of less than or equal to 10 mg/l (sensitive) and greater than or equal to 32 mg/l (resistant) are acceptable, then only a few of the Enterobacteriaceae in this study were resistant. These resistant organisms were amongst Enterobacter spp. and Citrobacter spp.