Study on carbapenemase and 16S rRNA methylase of imipenem-resistant Acinetobacter baumannii / 中华流行病学杂志

ABSTRACT

Objective To investigate the prevalence of 16S rRNA methylases gene in imipenem-resistant Acinetobacter baumannii isolates from China. Methods A total of 342 imipenem-resistant A.baumannii isolates were collected between December 2004 and December 2005, from 25 hospitals of China. Agar dilution was used to determinate the minimal inhibitory concentration (MIC) of these isolates. The homology of these isolates was analyzed by pulse-field gel electrophoresis (PFGE). Several 16S rRNA methylase genes and carbapenemase genes were detected by PCR-based assays and PCR products were sequenced. Results The rates of resistance to ampicillin-sulbactam, cefoperazone-sulbactam, tobramycin, and minocycline were 68.0%, 54.2%, 87.4%, and 75.9%, respectively. The rate of resistance to polymyxin E was 10.8%, the lowest among the tested agents. The rates of resistance to all other tested antimicrobial agents were more than 90%. The A.baumannii isolates belonged to 29 distinct clones. Among them, 6 clones were dominant, consisting of 303 isolates in total. All isolates contained the blaOXA-51-1ike gene (blaOXA-66) and 322 isolates contained the blaOXA-23-1ike gene. PCR with the ISAbal-OXA-23-like primers generated a PCR product in 314 isolates, and PCR with the ISAbal-OXA-51-1ike primers generated a PCR product in 13 strains. 221 armA-positive isolates were identified. Conclusion Most of the imipenem-resistant A.baumannii contained blaOXA-23, with ISAbal upstream of the gene. 16S rRNA methylase gene armA was widely distributed in these isolates. The results suggested that the spread of clones played an important role in the outbreak of imipenem-resistant A. baumannii in China.