Dissemination of clonal complex 2 Acinetobacter baumannii strains co- producing carbapenemases and 16S rRNA methylase ArmA in Vietnam

Background: Acinetobacter baumannii strains co-producing carbapenemase and 16S rRNA methylase are highly resistant to carbapenems and aminoglycosides. Methods: Ninety-three isolates of multidrug-resistant A. baumannii were obtained from an intensive care unit in a hospital in Vietnam. Antimicrobial susceptibility tests and whole genome sequencing were performed. Multilocus sequence typing and the presence of drug resistant genes were determined and a maximum-likelihood phylogenetic tree was constructed by SNP alignment of whole genome sequencing data. Results: The majority of isolates belonged to clonal complex 2 (ST2, ST570 and ST571), and carried carbapenemase encoding genes blaOXA-23 and blaOXA-66. Two isolates encoded carbapenemase genes blaNDM-1 and blaOXA-58 and the 16S rRNA methylase encoding gene armA and did not belong to clonal complex 2 (ST16). Conclusion: A. baumannii isolates producing 16S rRNA methylase ArmA and belonging to clonal complex 2 are widespread, and isolates co-producing NDM-1 and ArmA are emerging, in medical settings in Vietnam.