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

Abstract

Acinetobacter is an important cause of nosocomial infections, and it is often resistant to many antibiotics. In a search for alternative agents, three β-lactamase inhibitors (sulbactam, clavulanate, and tazobactam) and five β-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 non- baumannii strains were not. Imipenem was the most active agent among the compounds investigated. All three β-lactamase inhibitors had strong intrinsic activity, with sulbactam being the most active agent among the β-lactamase inhibitors studied.