Molecular characterization and genetic diversity of multidrug- and extensively drug-resistant A. baumannii clinical isolates

Objective: The increasing prevalence of multi-drug resistant (MDR) strains is now a serious menace for public health. The purpose of the study is to investigate the relationship between the variation of carbapenemases and antibiotic resistance profile among A. baumannii strains isolated from Tabriz, North-west Iran. Methods: A total of 127 A. baumannii isolates were obtained from two teaching hospitals in Tabriz, North-west Iran. Multiplex PCR was performed for the detection of carbapenemase-encoding genes. Furthermore, the genetic relationship of isolates was investigated by the enterobacterial repetitive intragenic consensus (ERIC)-PCR technique. Results: All isolates were resistant to carbapenem based on resistance to meropenem and imipenem. The frequency of multidrug-resistant (MDR) and extensively drug-resistant (XDR) was equal to 74.80% and 33.07% respectively. The most prevalent of MDR and XDR was related to patients up to 50 years (p < 0.05). The bla(OXA-)(23-like )genes were the most predominant among tested isolates 82 (64.5%), followed by bla(OXA-14)(3-like), 54 (42.51%); bla(OXA-72), 39 (30.7%). None of the isolates were positive for the bla(OXA-58)(-like) gene. There was a significant relationship between the presence of the bla(OXA-23) gene and the frequency of XDR strains (p < 0.01). Based on ERIC-PCR, 88 isolates were clustered into seven groups, while the remaining 21 were as single isolates. Most of the MDR isolates were related to B and C clusters (p < 0.05). The frequency of OXA(-143) and OXA(-72) was significantly high in A and B clusters (p < 0.05). This is the first report of the high incidence of bla(OXA-14)(3) and bla(OXA-72) positive A. baumannii strains in Iran. The genetic relatedness of A. baumannii isolates was high, indicating cross-transmission within hospitalized patients. Conclusion: A high prevalence of MDR and XDR A. baumannii strains with new resistance mechanisms was observed in our region. The incidence rate of OXA-type carbapenemases was different in the clusters classified by ERIC -PCR typing.