Characterization of bla(OxA-23) gene regions in isolates of Acinetobacter baumannii

Abstract

Background/purpose: To investigate the characterization of bla(OxA-23) gene regions in isolates of Acinetobacter baumannii from Taizhou Municipal Hospital.

Methods: Fifty-nine non-repetitive, multiresistant (including imipenem-resistant) isolates of A. baumannii were recovered from clinical infections in hospitalized patients from January 2010 to August 2011 in Taizhou Municipal Hospital (affiliated with Taizhou University) in China. These isolates were genotyped using pulsed-field gel electrophoresis (PFGE). bla(OxA-23) β-lactamase and associated genetic structures were analyzed using polymerase chain reaction (PCR), and recombination plasmids were analyzed by BamHI- or SacI- restriction enzyme digestion; predicted promoter structures of bla(OxA-23) genes were determined and compared using protein-protein BLAST analysis.

Results: Fifteen out of 59 isolates expressing imipenem-resistant A. baumannii clinical isolates acquired either a bla(OxA-23) β-lactamase gene. A new gene cluster (ISAba1-bla(OxA-23)-AMP) with three previously identified transposons (Tn2006, Tn2007, and Tn2008) and one previously identified gene cluster (ISAba1- bla(OxA-23)) was found in the isolates. Recombination plasmids were analyzed by restriction enzyme digestion.

Conclusion: Our results indicate that pattern A was the most prevalent molecular type based on PFGE, and that different clones might be widespread with a majority of ISAba1-bla(OxA-23) clonal lineages in the 15 PCR positive isolates of A. baumannii in the hospital.

Keywords: Genetic structure; ISAba1- bla(OxA-23)-AMP; ISAba1-bla(OxA-23); Tn2006; Tn2007; Tn2008; bla(OxA-23) genes.