Phenotypic and genetically evaluation of the prevalence of efflux pumps and antibiotic resistance in clinical isolates of Pseudomonas aeruginosa among burned patients admitted to Ghotbodin Shirazi Hospital

Pseudomonas aeruginosa is an important cause of nosocomial infections in burnt patients. Antibiotic resistance through various mechanisms is one of challenges for treatment of these patients. The mex efflux pumps play a vital role in the development of multiple resistances to antimicrobial drugs. This study aimed to analyze the prevalence of genes responsible for efflux pumps mexA-B-oprM and to investigate their phenotypes in the isolates.

In this cross-sectional study, 250 swabs were obtained from wounds of the patients suffering of burns levels 2 and 3 who admitted in Ghotbodin Shirazi hospital, Shiraz. Presence of P. aeruginosa isolates were confirmed by biochemical tests and PCR. Drug susceptibility, the phenotypic activity of efflux pumps and the presence of mex A, mex B genes were determined using disk diffusion method, cartwheel method and PCR methods, respectively.

In this study, 26.40% (66 cases) of patients with burn wounds were infected with P. aeruginosa. These bacteria were resistant to all antibiotics tested except for colistin. Totally, 66.66% of the isolates (44 cases) had an efflux pump, among them 42.92% and 87.87% of the isolates carried mexA and mexB genes, respectively.

Our finding showed that genotypic method is very accurate and reliable than phenotypic methods for detection of efflux pumps in clinical isolates of P. aeruginosa. Due to presence of the efflux pump genes in more than 90% of the P. aeruginosa isolates, analysis of the presence of these genes is very important for suggestion of an effective treatment model for the patients with bacterial infection.