Comparative Activity of Cefepime with Several Antimicrobials against Aerobic Gram-Negative and Gram-Positive Organisms Isolated from Patients across Canada in 1993

Abstract

To compare the activity of cefepime, a fourth-generation cephalosporin, with several available antimicrobials, in vitro susceptibility studies were carried out on bacteria commonly associated with various infections, including sepsis. Ten tertiary care hospital laboratories in six provinces provided 1276 clinically relevant isolates of aerobic Gram-negative bacilli and Gram-positive cocci during 1993. When the activity of each of the antimicrobials was determined against all isolates submitted, cefepime, piperacillin/tazobactam, imipenem and ciprofloxacin all had minimal inhibitory concentrations for 90% of the organisms (mic₉₀) two or more dilutions below the mic resistant category. Gentamicin’s mic₉₀ against all organisms tested was one dilution below the mic resistant category. The mic₉₀s of the third-generation cephalosporins, piperacillin and ticarcillin/clavulanate, for Enterobacter species fell in the resistant category. This is presumably due to constitutive high level chromosomal cephalosporinase production. The mic₉₀s of cefepime for Enterobacter species was three or more dilutions below the mic resistant category. The mic₉₀s of all antimcrobials against Staphylococcus aureus, with the exception of ceftazidime and piperacillin, had mic₉₀ categories two or more dilutions below the resistant category. The activity of cefepime, piperacillin/tazobactam, imipenem, ciprofloxacin and gentamicin make them excellent candidates for the empirical therapy of serious infections due to aerobic Gram-negative bacilli and S aureus.