In vitro activity of beta-lactamase inhibitors against clinical isolates of Acinetobacter species.

Acinetobacter is an important cause of nosocomial infections, and it is often resistant to many antibiotics. In a search for alternative agents, three beta-lactamase inhibitors (sulbactam, clavulanate, and tazobactam) and five beta-lactam antibiotics (imipenem, ceftazidime, ceftriaxone, cefotaxime, and piperacillin) were tested against 68 unique clinical isolates of Acinetobacter species. Minimum inhibitory concentrations were determined by a broth microdilution method. Using temperature sensitivity testing, we identified 59 strains as Acinetobacter baumannii, one as Acinetobacter haemolyticus, and eight as indeterminate biotype species. We demonstrated 41 of 59 (70%) strains of A. baumannii to be multiply resistant (susceptible only to amikacin and imipenem), whereas all the nonbaumannii strains were not. Imipenem was the most active agent among the compounds investigated. All three beta-lactamase inhibitors had strong intrinsic activity, with sulbactam being the most active agent among the beta-lactamase inhibitors studied.