Six-year retrospective survey of the resistance of Bacteroides fragilis group species to clindamycin and cefoxitin.

Two hundred and forty-six strains of the Bacteroides fragilis group, all clinical isolates, collected at the Wadsworth Veterans Administration Medical Center from 1977 to 1982, were tested for susceptibility to clindamycin and cefoxitin. There was no significant change in resistance to either clindamycin or cefoxitin over the time period tested for any individual species, nor for the B. fragilis group in toto. Striking differences in susceptibility to the two drugs were seen among species of the B. fragilis group. B. fragilis displayed resistance to cefoxitin (32 micrograms/ml) and clindamycin (8 micrograms/ml) of 0.0% and 0.8%, respectively, whereas B. thetaiotaomicron showed resistances of 12.7% to cefoxitin (32 micrograms/ml) and 9% to clindamycin (8 micrograms/ml). B. thetaiotaomicron, B. distasonis, and B. ovatus are distinctly more resistant to cefoxitin than B. fragilis and B. vulgatus. Similarly B. thetaiotaomicron and B. distasonis are much more resistant to clindamycin than are the other B. fragilis group species. It is apparent that determination of species within the B. fragilis group is important in evaluating a potential therapeutic regimen.