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Mutations in nalc gene of Mex AB-OprM efflux pump in carbapenem resistant Pseudomonas aeruginosa isolated from burn wounds in Yazd, Iran

  • Tafti, Fatemeh Akhavan1, 2
  • Eslami, Gilda3, 4
  • Zandi, Hengameh4, 1
  • Barzegar, Kazem5
  • 1 Department of Microbiology, School of Medicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
  • 2 Institute for Advanced Research and Education in Transfusion Medicine, Yazd, Iran
  • 3 Department of Parasitology and Mycology, School of Medicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
  • 4 Iran
  • 5 Department of English Language, School of Medicine, Shahid Sadoughi University of Medical Sciences and Health Services Yazd, Iran
Published Article
Iranian Journal of Microbiology
Tehran University of Medical Sciences
Publication Date
Feb 01, 2020
PMID: 32322377
PMCID: PMC7163040
PubMed Central


Background and Objectives: Burn wound infections have emerged as an important cause of morbidity and mortality in patients due to prolonged hospital stay. Pseudomonas aeruginosa , is the second cause of bacterial burn wound infections. Resistance mechanisms among P. aeruginosa are intrinsic or acquired. Intrinsic resistance mechanisms among P. aeruginosa isolates are inducible AmpC cephalosporinase, decrease of specific porin OprD, and overexpression of RND efflux pump. The aim of this study was detection of mutations in nalC gene in carbapenem resistant P. aeruginosa isolated from burn wounds. Materials and Methods: In this cross-sectional study, 180 burn-wound specimens were collected. Suspected lactose-negative colonies were identified by conventional biochemical methods. Kirby-Bauer and Etest methods were used for susceptibility testing. PCR and sequencing techniques were used for the detection of nalC mutation. Results: Out of 180 specimens received in the laboratory, 54 of isolates were isolated and identified as P. aeroginosa (30%). Of these isolates 20 (37%) were resistant to at least two carbapenems simultaneously. From these carbapenem resistant isolates, 19 (95%), 14 (70%), 14 (70%), 19 (95%) and 16 (80%) were resistant to imipenem, cefepime, piperacillin, ceftizoxime and gentamicin, respectively. Only 1 (2%) isolate was sensitive to all carbapenems and did not has mutation in nalC gene, 20 (37%) isolates were resistant to at least two carbapenems, and had mutations in nalC gene (Gly71▸Glu and Ser209▸Arg). Conclusion: As the results showed, mutation in efflux pump was observed in carbapenem resistant isolate and this confirmed that the indiscriminate use of antibiotics for treatment or prophylaxis can increase mutation in efflux pump.

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