Comparative in vitro activity of sitafloxacin against multidrug-resistant and carbapenem-resistant acinetobacter baumannii clinical isolates in Thailand

Abstract

The rapid emergence of multidrug-resistant Acinetobacter baumannii (MDRAB) is recognized as a significant health problem worldwide, including Thailand. Due to a limitation of treatment option, a new antimicrobial agent has been challenged. Sitafloxacin, a new fluoroquinolone antimicrobial agent, has shown a good in vitro activity against MDRAB and carbapenem-resistant A. baumannii (CRAB). The aim of this study was to evaluate in vitro activity of sitafloxacin and compare that with other antimicrobial agents against A. baumannii clinical isolates, focusing on multidrug-resistant A. baumannii and carbapenem-resistant A. baumannii (MDR-CRAB). All 350 A. baumannii clinical isolates were collected from thirteen tertiary care hospitals in all regions of Thailand. The minimum inhibitory concentrations (MICs) were determined by broth microdilution method. To determine rate of susceptibilities, a susceptible isolate with sitafloxacin was considered as MIC values of ≤ 2 μg/mL and ≤ 1 μg/mL. For other antimicrobial agents, MIC breakpoints were considered according to the Clinical and Laboratory Standards Institute (CLSI) 2018. Our study found that 278 clinical isolates were identified as MDR-CRAB. The MIC range, MIC50 and MIC90 of sitafloxacin against MDR-CRAB isolates were ≤ 0.0625-8 μg/mL, 1 μg/mL and 2 μg/mL, respectively. Additionally, almost of the colistin-resistant isolates were susceptible to sitafloxacin (92.86%). Sitafloxacin had a good activity against multidrug-resistant isolates in Thailand. Thus, sitafloxacin can be considered as an alternative choice for treatment of MDRAB and CRAB infections. Further studies are needed to evaluate treatment outcomes. © 2020 Faculty of Pharmacy.