Study On Molecular Epidemiology For The Related Genes And Plasmid Among Carbapenem-Resistant Acinetobacter Baumannii

ObjectiveThe present study is to investigate the characterization of carbapenem-resistant Acinetobacter baumannii isolated from the First Affiliated Hospital of Chengdu Medical College. The investigation performed among CRAB includes: detection of the related genes, evolutionary relationship, molecular epidemiology, and horizontal transfer mediated by plasmids, which will provide scientific basis to clinical treatment.Materials and MethodsOne hundred and ten clinical isolates of Acinetobacter baumannii, collected from 2012 to 2013 at the First Affiliated Hospital of Chengdu Medical College,which were tested for carbapenem antibiotic susceptibility, followed by a molecular analysis of carbapenemase genes, such as bla KPC, bla IMP, bla VIM-1, blaSIM, bla NDM-1,bla OXA-23, bla OXA-24, bla OXA-51, bla OXA-58 and bla OXA-235. Genetic relatedness of the isolates was characterised by multilocus sequence typing. Plasmid conjugation and sequencing was used to analyze the fuction of the plasmid carried by CRAB.ResultsAll of the 110 isolates carried recA, 16 S rRNA and bla OXA-51. Sixty seven of the110 isolates(60.9%) were resistant to carbapenem, 54(80.60%, 54/67) of which carried the bla OXA-23 gene. Most of 67 CRAB are classified as clone complex 92(CC92), and sequence type(ST) 92 was the most prevalent STs, followed by ST195,ST136, ST843 and ST75. One CRAB isolate of ST195 harbored plasmid pAB52(Genbank: KR030046). The toxin-antitoxin elements of pAB52 may be related to adaptation for A. baumannii’s growth.Conclusion1. The resistant mechanism of the CRAB from the First Affiliated Hospital of Chengdu Medical College is associated with the bla OXA-23 genes.2. CC92 is a major drug resistant complex clone in A. baumannii.3. One CRAB in the present study carried plasmid pAB52, which harbored toxin-antitoxin elements were supposed to be engaged in the adaptation of carbapenem resistance in A. baumannii.