In vitro activities of piperacillin or cefoperazone alone and in combination with beta-lactamase inhibitors against gram-negative bacilli.

We investigated in vitro activities of piperacillin or cefoperazone alone and in combination with beta-lactamase inhibitors against Gram-negative bacilli. Piperacillin/tazobactam 8:1 lowered resistance for Escherichia coli, Serratia marcescens, Enterobactaer cloacae, Klebsiella pneumoniae and imipenem-susceptible Acinetobacter baumannii. When piperacillin was combined with sulbactam 2:1 or 4:1, resistance against E. coli, S. marcescens, E. cloacae, extended spectrum beta-lactamase (ESBL)-K. pneumoniae and A. baumannii were reduced. MIC90 of cefoperazone against S. marcescens, E. cloacae, ESBL-K. pneumoniae and A. baumannii were >128 mg/L. Addition of sulbactam 1:1 or 2:1 enhanced antimicrobial activities. Addition of sulbactam to piperacillin or cefoperazone enhanced antimicrobial activities of GNB.