Evaluation of nalC mutations and mexA deregulation involved in multidrug resistance in Pseudomonas aeruginosa starins isolated from Guilan hospitals

Background: Pseudomonas aeruginosa is a gram-negative bacterium that continues to be a major cause of opportunistic nosocomial infections. In pseudomonas aeruginosa, several drug resistance mechanisms have been proposed such as nalC mutation and Overproduction of MexAB-OprM system. The aim of this study investigation of nalC mutations and MexA expression in drug resistant pseudomonas aeruginosa isolated from burned patients in Guilan hospitals.Materials and Methods: Pseudomonas aeruginosa isolated from burned patients were identified using standard methods. Drug susceptibility and MIC were determined from 45 clinical samples. 11 ciprofloxacin resistant strains were isolated and mutations in nalC gene were investigated in these strains by PCR-sequencing method. Then, the expression of MexA was evaluated by quantitative RT-PCR.Results: ciprofloxacin resistance range in the strains were between MIC =64 to 1024ʽg/ml. in this study, 64% of 11 resistant strains had mutations G71E, E153Q and S209R in nalC gene. Also, upregulation of MexA was revealed in the resistant strains.Conclusion: Overproduction of MexAB-OprM system in pseudomonas aeruginosa may lead to multidrug resistance in clinical isolates. Also, nalC inactivation is a reason of upregulation of MexAB-OprM. It seems that quinolone resistance in the isolates of Pseudomonas aeruginosa in Guilan were partly developed by nalC mutations and subsequently upregulation of MexA gene.

Keywords:

MexA , nalC , Pseudomonas aeruginosa , quinolone resistance