Molecular tracking of carbapenem-resistant Acinetobacter baumannii clinical isolates: a multicentre study over a 4-year period across eastern China.

Introduction. Colonization by carbapenem-resistant Acinetobacter baumannii (CRAB) causes therapeutic and economic problems for critically ill patients.Gap Statement. The analysis of CRAB in China was limited to certain regions.Aims. To investigate the antibiotic susceptibility, molecular characterization and clonal relationship among CRAB isolates from multiple hospitals of eastern China.Methodology. Isolates from 29 tertiary hospitals from September 2015 to September 2018 were recovered. All strains were analysed using antimicrobial susceptibility testing to detect their tolerance. PCR was also used to detect multiple β-lactamase genes. After multilocus sequence typing (MLST) of seven house-keeping genes. eBURST was used to assess clonal complexes and explore evolutionary relationships.Results. All isolates showed resistance to carbapenems, while remaining susceptible to colistin and tigecycline. All isolates were detected with bla OXA-51 gene by PCR, and 80.1 % harboured the bla OXA-23 gene. The prevalence of blaOXA-23 gene was remarkably increased from 50.7 % in 2015 to 90.5 % in 2018. Other genes such as bla OXA-24, bla OXA-58, bla IMP-2/4, bla VIM-2, bla SHV, bla AmpC and bla TEM were also obtained. While bla KPC, bla NDM-1, bla IMP-4 and bla SIM-1 were not found in these strains. MLST showed all isolates could be divided into 26 known sequence types (STs) and ten novel STs and 47.2 % isolates belong to ST195 and ST208. eBURST revealed clonal complex 92 as the major clonal complex (98.4 %), which includes 88.5 % (23/26) of known STs and 80 % (8/10) of unknown STs. Phylogenetic analysis also found that almost all CRAB isolates could cluster into one lineage, suggesting an epidemic of this CRAB lineage. This indicated severe nosocomial infections of CRAB in multiple hospitals of eastern China.Conclusion. An outbreak of ST195 and ST208 CRAB-resistant clones with bla OXA-23 gene might be happening in multiple hospitals in eastern China.