In vitro responses of Acinetobacter baumannii to two- and three-drug combinations following exposure to colistin and doripenem

Abstract

We compared in vitro killing of colistin, doripenem, and sulbactam by time-kill methods against Acinetobacter baumannii isolates collected from patients before and after colistin-doripenem treatment (initial and recurrent isolates, respectively). Colistindoripenem bactericidal activity against recurrent isolates was attenuated (mean log10 kill,-5.74 versus-2.88; P=0.01) but was restored by adding sulbactam. Doripenem MICs rather than colistin MICs correlated with the activity of colistin-doripenem. Among colistin-resistant isolates, colistin-doripenem-sulbactam combinations achieved greater killing than colistin-doripenem alone (-5.65 versus-2.43; P=0.04). Copyright © 2014, American Society for Microbiology. All Rights Reserved.