Background and objectives: Notwithstanding the increased prevalence ofAcinetobacter baumannii drug-resistant isolates, treatment options are progressively limiting. This study aims to provide a recent report on antibiotic susceptibility in burn wound isolates ofA. baumannii, and the importance of OXA beta-lactamases in carbapenem resistance.

Materials and methods: The susceptibility levels to different antimicrobial categories were determined among 84A. baumannii isolates from burn wound infection between 2016 and 2018. Multiplex PCR was used to detect OXA beta-lactamases genes, includingbla_OXA-51,bla_OXA-23,bla_OXA-24 andbla_OXA-58. ISAba-1 association withbla_OXA-51,bla_OXA-23 andbla_OXA-58 was detected by PCR mapping.

Results: All the isolates were determined as multidrug-resistant (MDR) and 69% as extensively drug-resistant (XDR). Different carbapenems MIC ranges (MIC₅₀ and MIC₉₀) were observed among the isolates harboringbla_OXA-like genes and isolates with the OXA-24-like enzyme showed higher carbapenems MIC ranges. The prevalence ofbla_OXA-51-like,bla_OXA-23-like,bla_OXA-24-like andbla_OXA-58-like were 100%, 53.57%, 41.66% and 30.95%, respectively. ISAba-1 insertion sequence was found to be upstream tobla_OXA-23-like andbla_OXA-58-like genes in 23 out of 45 (71.1%)bla_OXA-23-like-positive and 4 out of 23 (15.3)bla_OXA-58-like-positive isolates, respectively.

Conclusion: Resistance to carbapenems as the last resort for treatment ofA. baumannii infections is growing. This study, for the first time in Iran, has observed the increased frequency ofbla_OXA-24-like andbla_OXA-58-like genes and found an association between ISAba-1 andbla_OXA-58-like gene, which signifies the possible risk of increased diversity in OXA beta-lactamases and growth in carbapenem resistance.