Spread of imipenem-resistant Acinetobacter baumannii co-expressing OXA-23 and GES-11 carbapenemases in Lebanon

Abstract

Objectives The acquisition of carbapenemases by Acinetobacter baumannii is reported increasingly worldwide, but data from Lebanon are limited. The aims of this study were to evaluate the prevalence of imipenem-resistant A. baumannii in Lebanon, identify resistance determinants, and detect clonal relatedness.

Methods Imipenem-resistant A. baumannii were collected from nine Lebanese hospitals during 2012. Antimicrobial susceptibility, the cloxacillin effect, and ethylenediaminetetraacetic acid (EDTA) synergy were determined. Genes encoding carbapenemases and insertion sequence IS Aba1 were screened via PCR sequencing. IS Aba1 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 PCR (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. A positive cloxacillin test indicated ADCs, while EDTA detection strips were negative. Genotyping indicated that 90% of isolates co-harbored bla OXA-23 and bla GES-11 . The remaining strains had bla OXA-23 , bla OXA-24 , bla GES-11 , or bla OXA-24 with bla GES-11 . IS Aba1 was located upstream of bla ADC and bla OXA-23 in 97% and 100% of isolates, respectively. ERIC-PCR fingerprinting revealed 18 pulsotypes spread via horizontal gene transfer and clonal dissemination.

Conclusion This survey established baseline evidence of OXA-23 and GES-11-producing A. baumannii in Lebanon, indicating the need for further surveillance.