Molecular Epidemiology of Clinical Isolates of Carbapenem-Resistant Acinetobacter spp. from Chinese Hospitals

Abstract

ABSTRACT Carbapenem resistance in Acinetobacter spp. is an emerging problem in China. We investigated the molecular epidemiology and carbapenemase genes of 221 nonrepetitive imipenem-resistant clinical isolates of Acinetobacter spp. collected from 1999 to 2005 at 11 teaching hospitals in China. Genotyping by pulsed-field gel electrophoresis (PFGE) found 15 PFGE patterns. Of these, one (clone P) was identified at four hospitals in Beijing and another (clone A) at four geographically disparate cities. Most imipenem-resistant isolates exhibited high-level resistance to all β-lactams and were only susceptible to colistin. bla OXA-23 -like genes were found in 97.7% of isolates. Sequencing performed on 60 representative isolates confirmed the presence of the bla OXA-23 carbapenemase gene. Analysis of the genetic context of bla OXA-23 showed the presence of IS Aba1 upstream of bla OXA-23 . All of the 187 A. baumannii isolates identified by amplified RNA gene restriction analysis carried a bla OXA-51 -like oxacillinase gene, while this gene was absent from isolates of other species. Sequencing indicated the presence of bla OXA-66 for 18 representative isolates. Seven isolates of one clone (clone T) carried the plasmid-mediated bla OXA-58 carbapenemase gene, while one isolate of another clone (clone L) carried the bla OXA-72 carbapenemase gene. Only 1 isolate of clone Q carried the bla IMP-8 metallo-β-lactamase gene, located in a class 1 integron. Of 221 isolates, 77.8% carried bla PER-1 -like genes. Eleven different structures of class 1 integrons were detected, and most integrons carried genes mediating resistance to aminoglycosides, rifampin, and chloramphenicol. These findings indicated clonal spread of imipenem-resistant Acinetobacter spp. and wide dissemination of the OXA-23 carbapenemase in China.