Investigation of carbapenem resistant Acinetobacter baumannii ST2 in Iran

This study investigated carbapenem resistance among Acinetobacter baumannii isolated from respiratory specimens. Epidemiological relationship of the isolates was also evaluated. In this study, 81 respiratory specimens of A. baumannii from AL Zahra Hospital were confirmed by phenotypic and genotypic methods. Antimicrobial susceptibility was performed by disc diffusion method. Carbapenem resistance genes were identified by PCR. The isolates were typed by RAPD-PCR and multilocus sequence typing (MLST) methods. All isolates were resistant to imipenem and 80 isolates to meropenem. Frequency of oxacillinase genes was as follows: blaOXA-23 gene was positive in 74 (91.3%), blaOXA-24 gene in 50 (61.7%) and blaOXA-58 was not found in any isolates. On the other hand 22 (27.2%) isolates contained blaIMP-1, 3 (3.7%) isolates contained blaIMP-2 gene, 5 (6.2%) isolates contained blaVIM-1, 4 (5%) isolates had blaVIM-2 and none of the isolates had blaSIM-1 gene. RAPD-PCR typing identified 16 different patterns, with one pattern being the most frequent one in 26 isolates. In MLST 6 different sequence types were identified, the most predominant being ST2 belonging to clonal complex 2. The results of this study showed high resistance to carbapenems as well as high abundance of oxacillinase genes.