Abstract

Resistance of Gram-negative bacilli to third-generation cephalosporins has been increasing due to the production of extended-spectrum ?-lactamases. In this work, the activities of cefepime, cefotaxime, ceftazidime, and aztreonam, alone and in association with clavulanic acid, against isolates of Klebsiella pneumoniae and Escherichia coli are compared. These isolates produce extended-spectrum ?-lactamases as shown by the synergy tests and by the decrease in the MICs of cephalosporins in the presence of clavulanic acid. Cefepime was the most active compound against these microorganisms. In addition, the microorganisms exhibited lower frequencies of resistance to this cephalosporin. © 2001 Elsevier Science Inc.