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Molecular characterization of carbapenem-resistant <i>Acinetobacter baumannii</i> isolated from pediatric burns patients in an Iranian hospital

Abazar Pournajaf
Ramazan Rajabnia
Shabnam Razavi
Sana Solgi
Abdollah Ardebili
Sajad Yaghoubi
Mahmoud Khodabandeh
Yousef Yahyapour
Behzad Emadi
Gholamreza Irajian


Purpose: To survey the molecular characteristics of imipenem-resistant Acinetobacter baumannii obtained from pediatric burns patients in a teaching hospital in Tehran, Iran.
Methods: Over a 10-month period, 73 non-duplicate A. baumannii strains were collected from pediatric burns patients admitted to Motahari Burn and Reconstruction Center, Tehran, Iran. The resistance profile of several antimicrobials was determined. Metallo-β-lactamase (MBL)-producing isolates were identified using double-disk synergy and an MBL E-test. Polymerase chain reaction (PCR) was carried out to detect the following β-lactamase-encoding elements: blaVIM, blaIMP, blaSIM, blaSPM, blaGIM, blaNDM, blaAIM, blaDIM, blaKPC, blaOXA-23/24/51, and blaOXA-58. The types of integrons were also identified using PCR.
Results: Out of the 73 collected strains, 92.4 and 38.3 % of the isolates were multidrug-resistant (MDR) and extensively drug-resistant (XDR), respectively. Colistin was the most effective antibiotic. It was found that 94.5 % of the strains were resistant to imipenem, as determined both by disk agar diffusion and MIC E-test methods. Based on double disk synergy and E-test, 78.1 and 83.5 % of the isolates, respectively, were MBL producers. The prevalence of blaOXA-23 and blaOXA-24 were 75.4 and 39.1 %, respectively. The results also indicate that 62.3, 30.4, and 4.3 % of the isolates were positive for blaVIM, blaIMP and blaNDM genes, respectively. Furthermore, 16.4, 76.1, and 7.5 % of the isolates carried intI, intII, and intIII genes, respectively.
Conclusion: The increased frequency of carbapenem-resistant A. baumannii in burns cases underlines the importance of choosing an appropriate antibacterial regimen based on antibiotic susceptibility profile. Rapid identification of carbapenemase-producing strains would be helpful for selecting suitable antimicrobial therapy and preventing further spread of their encoding genes.

Keywords: Carbapenem-resistant Acinetobacter baumannii, Pediatric burns, Integron, β-lactamase genes