Resistance traits and molecular characterization of multidrug-resistant Acinetobacter baumannii isolates from an intensive care unit of a tertiary hospital in Guangdong, southern China

Purpose This study aims to characterize antimicrobial resistance (AMR) of all the non-duplicated Acinetobacter baumannii strains isolated from an intensive care unit in a tertiary hospital during the period of January 1 to December 31, 2015. Methods A. baumannii ( n = 95 strains) isolated from patients was subjected to antimicrobial susceptibility test (AST) by Vitek 2 Compact system to determine minimum inhibitory concentrations, followed by genotyping by enterobacterial repetitive intergenic consensus-PCR (ERIC-PCR). Resistance genes of interest were PCR amplified and sequenced. Results All isolates were qualified as MDR, with a resistance rate of > 80% to 8 antimicrobials tested. In terms of beta-lactamase detection, the bla OXA23 , bla TEM-1 , and armA genes were detected frequently at 92.63%, 9 1.58%, and 88.42%, respectively. The metallo-β-lactamase genes bla IMP and bla VIM were undetected. Aph (3’)-I was detected in 82 isolates (86.32%), making it the most prevalent aminoglycoside-modifying enzyme (AMEs) encoding gene. In addition, ant (3″)-I was detected at 30.53%, while 26.32% of the strains harbored an aac (6')-Ib gene. ERIC-PCR typing suggested moderate genetic diversity among the isolates, which might be organized into 10 distinct clusters, with cluster A ( n = 86 isolates or 90.53%) being the dominant cluster. Conclusions All of the A. baumannii strains detected in the ICU were MDR clones exhibiting extremely high resistance to carbapenems and aminoglycosides as monitored throughout the study period. They principally belonged to a single cluster of isolates carrying bla OXA23 and armA co-producing different AMEs genes.