Phenotypic and Genotypic Typing of Carbapenem-Resistant Acinetobacter baumannii Isolates from Lebanon

Abstract

Infections caused by Carbapenem-Resistant Acinetobacter baumannii (CRAB) have become an essential healthcare-associated problem. We used whole-genome sequencing (WGS) to characterize A. baumannii collected from a hospital in Lebanon. The genotypic relatedness was assessed by pulsed-field gel electrophoresis (PFGE), multi-locus sequence typing (MLST), and whole-genome SNP-based phylogenetic analysis (wg-SNP). A. baumannii PCR-based replicon typing (AB-PBRT) was also used to analyze the plasmid content. PFGE demonstrated that most isolates that belonged to a unique clonal type were assigned to ST2 of the international clone II. Phenotypic antimicrobial susceptibility testing revealed that the isolates were extensively drug-resistant (XDR). Intrinsic β-lactam resistance genes, including blaADC25 (Acinetobacter-Derived Cephalosporinase) and the blaOXA66 (a variant of blaOXA51), were among the common resistance determinants. AB-PBRT, which categorizes A. baumannii plasmids into homology groups (GRs) based on the nucleotide homology of their respective replicase genes, showed that the isolates were mainly positive for GR2 and GR6. A. baumannii is a nosocomial pathogen that is difficult to control. WGS analysis showed the relatedness of the studied CRAB isolates and mobile genetic elements and revealed the enhanced transmission prospects of A. baumannii between and among patients. WGS and interventional trials are needed to define and prevent the spread of XDR microbial pathogens.