Iranian Journal of Medical Microbiology

Background and Aim: The rising trend of antibiotic resistance among A. baumannii strains has become a global concern. The most common mechanism of resistance is betalactamase production with genes transferring on mobile genetic elements such as plasmids. The aim of this study was to determine the frequency of bla_NDM, bla_GIM, bla_AIM, bla_DIM and   bla_VIM type genes among A. baumannii isolates from hospitalized patients in Tehran, Iran.

Materials and Methods: from May 2012 to July 2013, 108 A. baumannii strains were isolated from blood, wound, urine, sputum and respiratory tract of hospitalized patients in Loghman hakim and Milad hospitals. Antibiotic susceptibility tests were performed by Kirby-Bauer disc diffusion and broth microdilution methods according the CLSI guidelines. The frequency of MBL (Metallo-Beta-Lactamase) producers was evaluated by CDDT. The β-lactamases genes were detected by PCR method.

Results: The resistance of A. baumannii isolates against tested antibiotics were as follows: 103 (95.4%) to ceftazidime, 108 (100%) to cefotaxime, 105 (95.7%) to cefepime, 99 (91.7%) to imipenem, 99 (91.7%) to meropenem, 87 (80.6%) to amikacin, 105 (97.2%) to piperacillin, 100 (92.6%) to ciprofloxacin, 103 (95.4%) to piperacillin/tazobactam, 44 (40.7%) to gentamicin, 106 (98.1%) to ampicillin/sulbactam, 106 (98.1%) to co-trimoxazole, 87 (80.6%) to tetracycline, and 1 (1.8%) to colistin. Using combined disk diffusion test, 86 (86.86%) were MBL producers. The prevalence of bla_VIM-1 gene was 15 (17.44%) and other genes were not detected.

Conclusions: The prevalence of MBLs-producing A. baumannii strains detected in this study is a major concern and highlights the need for infection control measures such as antibiotic management protocols and rapid identification of resistant strains.