Emergence of blaOXA-Carrying Carbapenem Resistance in Multidrug-Resistant Acinetobacter baumannii in the Intensive Care Unit

Background Emergence of multidrug-resistant (MDR) Acinetobacter baumannii infections is becoming a worldwide threat to hospitalized patients, particularly in intensive care units. Objectives The aim of this study was to investigate the antimicrobial susceptibility patterns and prevalence of bla_OXA-type carbapenemases of A. baumannii isolates in a teaching hospital in Iran. Patients and Methods The study included a total of 40 isolates of carbapenem-resistant A. baumannii, obtained from 103 tracheal tubes in hospitalized ICU patients. Antimicrobial susceptibility testing was performed according to CLSI guidelines. The bla_OXA-51, bla_OXA-23, bla_OXA-24, bla_OXA-58, and ISAba1 genes were detected by PCR. Results All of the A. baumannii isolates were resistant to imipenem and meropenem, and 100% of the isolates were MDR. The bla_OXA-51 and ISAba1 genes were detected in 100% of the isolates. bla_OXA-23 and bla_OXA-24 were detected in 90% and 40% of the isolates, respectively, but bla_OXA-58 was absent in the A. baumannii isolates. In addition, 32.5% of carbapenem-resistant strains contained at least three genes encoding bla_OXA-type carbapenemase. Colistin and polymyxin B were the most effective antibiotics. The sole risk factor for infection of hospitalized patients with carbapenem-resistant Acinetobacter strains was age over 40 years (P = 0.042). The mortality rate was 27.5%. Conclusions These findings signify the alarming spread of OXA genes in A. baumannii strains in our intensive care unit. The spread of carbapenem-resistant Acinetobacter strains has serious health implications and requires the application of strict infection-control measures.