Objectives: Acquisition of carbapenemases by Acinetobacter baumannii is increasingly reported worldwide, but data from Lebanon are limited. The aim of this study was to evaluate prevalence of imipenem-resistant A. baumannii in Lebanon, identify resistance determinants, and detect clonal relatedness.
Methods: Imipenem-resistant A. baumannii were collected from 9 Lebanese hospitals during 2012. Antimicrobial susceptibility, cloxacillin effect, and EDTA synergy were determined. Genes encoding carbapenemases and insertion sequence ISAba1 were screened via PCR-sequencing. ISAba1 position relative to genes encoding Acinetobacter-derived cephalosporinases (ADCs) and OXA-23 was studied by PCR-mapping. Clonal linkage was examined by enterobacterial repetitive intergenic consensus (ERIC)-PCR.
Results: Out of 724 A. baumannii isolated in 2012, 638 (88%) were imipenem-resistant. Of these, 142 were analyzed. Clavulanic acid-imipenem synergy suggested carbapenem-hydrolyzing extended-spectrum-β-lactamase. Positive cloxacillin test indicated ADCs, while EDTA-detection strips were negative. Genotyping indicated that 90% of isolates co-harbored blaOXA-23 and blaGES-11. Remaining strains had blaOXA-23, blaOXA-24, blaGES-11, or blaOXA-24 with blaGES-11. ISAba1 was located upstream of blaADC and blaOXA-23 in 97% and 100% of isolates respectively. ERIC-PCR fingerprinting revealed 18 pulsotypes spread via horizontal gene transfer and clonal dissemination.
Conclusions: This survey established baseline evidence of OXA-23 and GES-11-producing A. baumannii in Lebanon, illustrating need for further surveillance.