Worldwide dissemination of the blaOXA-23 carbapenemase gene of Acinetobacter baumannii

Abstract

To assess dissemination of OXA-23-producing strains of Acinetobacter baumannii, we obtained 20 carbapenem-resistant, OXA-23-producing isolates from different regions. Their clonal relationship was assessed by pulsed-field gel electrophoresis and multilocus sequence typing. We identified 8 sequence types, including 4 novel types. All except 2 strains belonged to 2 main European clonal lineages. The blaOXA-23 gene was either located on the chromosome or on plasmids and associated with 4 genetic structures.

Figure 1

Genetic structures associated with the bla_OXA-23 gene of Acinetobacter baumannii. A) Tn2006 from isolates 240, 512, 810, 859, 883 and AUS (ST22/ST2). B) Tn2008 from isolate 614. C) Tn2007 from isolates Ab14, BEL, and DOS. D) ISAba1 from isolates AS3, 1190, 861, and 877. Boundaries of Tn2006, Tn2007, and Tn2008 are indicated with the target site duplication likely generated by transposition events underlined. The 7-bp difference in the site of insertion of ISAba1 for isolate 614 is double-underlined. The open reading frame 1 (orf1), orf2, and orf3 genes of unknown function is indicated. tnpA, gene encoding a putative transposase; ATPase, gene encoding the putative AAA ATPase; DEAD, gene encoding the putative DEAD (Asp-Glu-Ala-Asp) helicase; DNAmethyl, DNA methylase.

Figure 2

Pulsed-field electrophoresis (PFGE) profiles of ApaI-digested genomic DNA from strains of Acinetobacter baumannii. PFGE types, European clone types, and multilocus sequence typing (MLST) results are shown. *ST, sequence type determined by Bartual et al. (19) compared with ST determined by Nemec et al. (20). Lane M, molecular size markers (48.5 kb).