Molecular Characterization of Insertion Sequences Upstream of blaOXA Genes and Their Association with Carbapenem Resistant in Acinetobacter baumannii from Baghdad

Carbapenem-resistant Acinetobacter baumannii (CRAB) has emerged as a serious global public health issue, primarily caused by the dissemination and overexpression of blaOXA-type genes. Investigate the genetic association between insertion sequences and blaOXA genes in A. baumannii isolates is the aim of the present. Sixty-five A. baumannii were isolated from both genders and different sources in the laboratories of several hospitals in Baghdad. All 65 isolate were diagnosed by VITEK-II system and by PCR to detect 16s rRNA and the blaOXA-51 genes. Antimicrobial susceptibility test was done by Kirby-Bauer method for 14 antimicrobial agents. Minimum inhibitory concentration (MIC) to colistin and meropenem also done, the results showed out of 65 isolates, 37 (56.9%) were carbapenem resistance and all the isolates showed high resistant percentage antimicrobial agents under study, which included MDR, XDR and PDR patterns with ‏predominance in XDR. All 37 CRAB isolates demonstrate high MIC values against meropenem. Carbapenem-resistant A. baumannii which were positive for both blaOXA genes and ISs were further subjected to PCR to investigate the association between insertion sequences and resistant genes, and out of 27 isolates were positive for both ISAba1 and blaOXA-23 gene, 20 (74.07%) were have ISAba1 upstream blaOXA-23 gene and out of 27 isolates that were positive for both ISAba1 and blaOXA-24 gene, 15 (55.55%) were have ISAba1 upstream blaOXA-24 gene. In the other hand only 3 (8.11%) isolates have ISAba1 upstream blaOXA-51 gene out of 37 isolates positive for both ISAba1 and blaOXA-51 gene, and all 16 (100%) isolates which were positive for both ISAba1 and blaOXA-58 were have ISAba1 upstream blaOXA-58 gene. Also, out of 18 isolates positive for both ISAba3 and blaOXA-23, 3(16.67%) of isolates were have ISAba3 upstream blaOXA-23 gene. The results confirmed the role of insertion sequences in increase resistance to carbapenem, and when ISs located upstream of blaOXA genes this correlated with higher meropenem MIC values. Sequencing confirmed the identity of the investigated genes.