Criteria for in vitro susceptibility testing of cefotetan. Correlations with clinical and bacteriologic responses.

Standardized in vitro susceptibility testing criteria and quality-control guidelines for cefotetan have been well documented in the scientific literature. Cefotetan and cefoxitin differ in their in vitro spectrums of activity and cannot be used interchangeably for in vitro tests. In vitro susceptibility information failed to correlate with clinical or bacteriologic responses of treated patients when 314 anaerobic bacteria from 145 patients were evaluated. All cefotetan-resistant anaerobic bacteria were eradicated by cefotetan therapy, and 93 percent of patients with resistant strains were clinically curved. Most members of the Bacteroides distasonis-ovatus-thetaiotaomicron group of pathogens were resistant in vitro, but only one strain persisted after cefotetan therapy for a 96.6 percent cure rate. There was better correlation when 2,336 aerobic bacteria from 1,630 infected body sites were considered. Microorganisms susceptible or moderately susceptible by in vitro tests were equally responsive to therapy (95 percent of patients clinically cured and 94 percent of isolates eradicated). However, strains that were resistant by in vitro test criteria were less likely to respond clinically. Development of resistance during therapy or superinfections (1.7 percent) were not found to be clinically important problems with cefotetan chemotherapy.