In vitro activity of cefepime and cefpirome compared to other third-generation cephem antibiotics against gram-negative nosocomial pathogens

The in vitro activities of new expanded spectrum of fourth-generation cephalosporins, cefepime and cefpirome, were compared with those of three third-generation cephalosporins, cefoperazone, ceftazidime, and ceftriaxone, that are commonly used in the treatment of serious infections caused by aerobic gram-negative bacteria. The agar dilution method described by the US National Committee for Clinical Laboratory Standards was used to determine the minimum inhibitory concentrations of antibiotics tested. 302 clinical isolates, representing a cross-section of Klebsiella and Enterobacter species and Pseudomonas aeruginosa were tested. Cefepime was considerably more active than other antibiotics tested, against Klebsiella species and Enterobacter species, and demonstrated activity similar to ceftazidime against Pseudomonas aeruginosa. Ceftazidime was active against Pseudomonas aeruginosa but was less potent against Enterobacter species. Cefoperazone and ceftriaxone were less active than ceftazidime against Pseudomonas aeruginosa. Cefepime had slightly greater activity than cefpirome against the gram-negative bacteria tested. However, cefepime and cefpirome were found to be highly active against many resistant organisms that traditionally have been difficult to treat.