Molecular epidemiology of carbapenem-resistant Acinetobacter baumannii strains in Belgian acute-care hospitals

Abstract

Objectives: To describe the genotypic epidemiological distribution and the antibiotic resistance mechanisms of recent carbapenem-resistant Acinetobacter baumannii (CRAb) strains recovered from clinical samples in Belgium. Methods: A total of 40 clinical isolates of CRAb collected by the national reference center from 19 acute-care hospitals through national microbiological surveillance in 2014 and 2017 were analysed in this study. The isolates were tested for antimicrobial susceptibility by broth microdilution and determined for carbapenemase-encoding genes by multiplex PCR targeting major carbapenemases families. Isolates were subjected to whole-genome sequencing (WGS) with Illumina technology and the complete chromosomal sequences were de novo assembled. Genome analysis was performed to identify intrinsic and acquired resistance determinants and to characterize clonal lineage according to the sequence type (ST). Results: All 40 isolates were resistant to carbapenems and exhibited extensively drug-resistant phenotype with blaOXA-23 (n=29) being the most abundant detected acquired AMR gene with 38 isolates encoding at least two different types of OXA enzymes. The majority of the isolates were globally disseminated clones of ST2 (n=25) while less frequent sequence types such as ST636 (n=6), ST1 (n=3), ST85 (n=2) and per one isolate from ST604, ST215, ST158 and ST78 were also detected. Conclusions: We have detected extensively drug-resistant globally occurring clones of A. baumannii ST1 and ST2 throughout Belgium as well as other sporadic ST including ST636 causing local outbreaks. Our results show the presence of high-risk clones of A. baumannii with common travel importation and the crucial need of constant surveillance.