Resistance Traits and Molecular Characterization of Multidrug-resistant Acinetobacter baumannii Isolates from an Intensive Care Unit of a Tertiary Hospital in Guangdong, Southern China

Abstract Purpose: This study aims to characterize antimicrobial resistance (AMR), with particular reference to carbapenems and aminoglycosides, in MDR A. baumannii isolates recovered from an intensive care unit in a tertiary hospital. Methods: A. baumannii (n = 95 strains) isolated from patients were 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 blaOXA23 and blaTEM-1 genes were detected frequently at 92.63% and 91.58%, respectively. The metallo-β-lactamase genes blaIMP, blaVIM, and blaNDM 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 harboured 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 a dominant cluster of epidemic clones.Conclusions: Substantial fractions of the A. baumannii strains prevailing 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 blaOXA23 and armA co-producing different AMEs genes.