Antibiotic resistance pattern of Acinetobacter baumannii from burns patients: increase in prevalence of bla(OXA-24-like) and bla(OXA-58-like) genes

BACKGROUND AND OBJECTIVES: Notwithstanding the increased prevalence of Acinetobacter baumannii drug-resistant isolates, treatment options are progressively limiting. This study aims to provide a recent report on antibiotic susceptibility in burn wound isolates of A. baumannii, and the importance of OXA beta-lactamases in carbapenem resistance. MATERIALS AND METHODS: The susceptibility levels to different antimicrobial categories were determined among 84 A. baumannii isolates from burn wound infection between 2016 and 2018. Multiplex PCR was used to detect OXA beta-lactamases genes, including bla(OXA-51), bla(OXA-23), bla(OXA-24) and bla(OXA-58). ISAba-1 association with bla(OXA-51), bla(OXA-23) and bla(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 (MIC(50) and MIC(90)) were observed among the isolates harboring bla(OXA-like) genes and isolates with the OXA-24-like enzyme showed higher carbapenems MIC ranges. The prevalence of bla(OXA-51-like), bla(OXA-23-like), bla(OXA-24-like) and bla(OXA-58-like) were 100%, 53.57%, 41.66% and 30.95%, respectively. ISAba-1 insertion sequence was found to be upstream to bla(OXA-23-like) and bla(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 of A. baumannii infections is growing. This study, for the first time in Iran, has observed the increased frequency of bla(OXA-24-like) and bla(OXA-58-like) genes and found an association between ISAba-1 and bla(OXA-58-like) gene, which signifies the possible risk of increased diversity in OXA beta-lactamases and growth in carbapenem resistance.