PURPOSE

The worldwide emergence and clonal spread of carbapenem-resistant Acinetobacter baumannii (CRAB) is of great concern. In the present study, we determined the mechanisms of antimicrobial resistance, virulence gene repertoire and genomic relatedness of CRAB isolates circulating in Serbian hospitals.

METHODS

CRAB isolates were analyzed using whole-genome sequencing (WGS) for the presence of antimicrobial resistance-encoding genes, virulence factors-encoding genes, mobile genetic elements and genomic relatedness. Antimicrobial susceptibility testing was done by disk diffusion and broth microdilution methods.

RESULTS

Eleven isolates exhibited an MDR resistance phenotype, while four of them were XDR. MIC for meropenem and imipenem were > 64 µg/mL and 32 µg/mL, respectively. While all CRABs harbored bla variant of bla gene, those assigned to ST2, ST636 and ST492 had blabla and bla variants, respectively. The following acquired carbapenemases-encoding genes were found: bla (n = 12), bla (n = 3), and bla(n = 5), and were mapped to defined mobile genetic elements. MLST analysis assigned the analyzed CRAB isolates to three Pasteur sequence types (STs): ST2, ST492, and ST636. The Majority of strains belonged to International Clone II (ICII) and carried tested virulence-related genes liable for adherence, biofilm formation, iron uptake, heme biosynthesis, zinc utilization, serum resistance, stress adaptation, intracellular survival and toxin activity.

CONCLUSION

WGS elucidated the resistance and virulence profiles of CRABs isolated from clinical samples in Serbian hospitals and genomic relatedness of CRAB isolates from Serbia and globally distributed CRABs.