Distribution of OXA-Type Class D β-Lactamase Genes Among Nosocomial Multi Drug Resistant Acinetobacter baumannii Isolated in Tehran Hospitals

Multiple drug-resistant strains of Acinetobacter have become common in hospitals worldwide. The problem becomes more acute with increasing resistance to carbapenems, the last resort in the treatment of hospital acquired Acinetobacter baumannii infections.. The current study was conducted to determine the antimicrobial susceptibility patterns and prevalence of OXA-type carbapenemases, among clinical isolates of A. baumannii, in Tehran hospitals, Iran.. Isolates were identified as A. baumannii by PCR with specific primers for bla OXA-51-like gene. Their susceptibilities to different antibiotics were determined using disk diffusion method. Isolates were then subjected to multiplex-PCR targeting bla oxa-51, bla oxa-24, blaoxa-23 and bla oxa-58 genes.. Results showed that 123 of 131 (93.89%) Acinetobacter species, possessed bla oxa-51-like gene and were identified as A. baumannii. 54.47% of isolates were resistant to amikacin, 67.47% resistant to imipenem and 84.55% resistant to meropenem. All isolates were susceptible to colistin and polymixin B. 43 of 123 A. baumannii isolates (34.95%) were MDR. These isolates were resistant to amikacin, ciprofloxacin, imipenem, cefrazidim. Among 123 isolates, 100(81.3 %) had an acquired oxa-23like carbapenemase 10 (8.1%) possessed oxa-24-like, and 1 (0.81%) possessed oxa-58-like carbapenemase.. The present study showed that bla OXA-23-like was the most frequent carbapenemase identified among carbapenem-resistant A. baumannii isolated in Tehran hospitals. Evaluation of antibiotic resistance genes in A. baumannii, is necessary to control further dissemination of these antibiotic resistant genes..