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Acinetobacter baumannii is one of nosocomial pathogen which emerges as multidrug-resistance worldwide. Multidrugresistant A. baumannii (MDRAB) and carbapenem-resistant A. baumannii (CRAB) are highly concerned due to limitation of therapeutic options. Antibacterial activity of biapenem was explored in order to overcome bacterial resistance. A total of 412 A. baumannii clinical isolates from 13 tertiary care hospitals in Thailand were collected. MIC values of biapenem and comparators; imipenem, meropenem, colistin, sulbactam, ciprofloxacin ceftazidime and fosfomycin sodium, were determined by broth microdilution method in accordance with the Clinical and Laboratory Standards Institute (CLSI) guidelines (2016). In total, 320 isolates (77.67%) were MDRAB and 328 isolates (79.61%) were CRAB while 58 isolates (14.07%) were colistin-resistant AB. A. baumannii showed widespread resistance to ceftazidime, ciprofloxacin and carbapenems in more than 90% of the strains; resistance to sulbactam, fosfomycin, and colistin were 85%, 60%, and 15% respectively. By comparison among carbapenems, biapenem showed MIC50/90 of 16/32 which were at least 2 folds lower than imipenem and meropenem (MIC50/90; 32/128, 32/64, respectively). In addition, 15% of imipenem and meropenemresistant A. baumannii were susceptible to biapenem. Also, 19% of colistin-resistant A. baumannii were susceptible to biapenem. Although more than 90% of MDRAB and CRAB were resistant to carbapenems, biapenem showed a good activity over other carbapenems. This drug might be a therapeutic option mono or combination therapy besides other antimicrobial agents. [ABSTRACT FROM AUTHOR]

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 carbapenemresistant 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 carbapenemresistant 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 MDRCRAB 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. [ABSTRACT FROM AUTHOR]