OXA- and GES-type β-lactamases predominate in extensively drug-resistant Acinetobacter baumannii isolates from a Turkish University Hospital

We determined the antibiotic susceptibility and genetic mechanisms of resistance in clinical strains of Acinetobacter baumannii from Istanbul, Turkey. A total of 101 clinical strains were collected between November 2011 and July 2012. Antimicrobial susceptibility was performed using the Vitek 2 Compact system and E-test. Multiplex PCR was used for detecting blaOXA-51-like, blaOXA.-23-like, blaOXA-40-like and blaOXA-58-like genes. ISAba1, blaIMP-like, blaVIM-like, blaGES, blaVEB, blaPER-2, aac-3-Ia and aac-6'-Ib and NDM-1 genes were detected by PCR and sequencing. By multiplex PCR, all strains were positive for blaOXA-51, 79 strains carried blaOXA-23 and one strain carried blaOXA-40. blaOXA-51 and blaOXA-23 were found together in 79 strains. ISAba1 element was detected in 81 strains, and in all cases it was found upstream of blaOXA-51. GES-type carbapenemases were found in 24 strains (GES-11 in 16 strains and GES-22 in 8 strains) while blaPER-2, blaVEB-1, blaNDM-1, blaIMP- and blaVIM-type carbapenemases were not observed. Aminoglycoside modifying enzyme (aac-3-Ia and aac-6'Ib) genes were detected in 13 and 15 strains, respectively. Ninety-seven (96%) A. baumannii strains were defined as MDR and of these, 98% were extensively drug resistant (sensitive only to colistin). Colistin remains the only active compound against all clinical strains. As seen in other regions, OXA-type carbapenemases, with or without an upstream ISAba1, predominate but GES-type carbapenemases also appear to have a significant presence. REP-PCR analysis was performed for molecular typing and all strains were collected into 12 different groups. To our knowledge, this is the first report of GES-11 and OXA-40 in A. baumannii from Turkey.