Characteristics of multiresistant Pseudomonas aeruginosa isolates from burn patients in Iran.

Infections caused by multidrug resistant (MDR) Pseudomonas aeruginosa isolates in burn patients restrict therapeutic strategies. The current study aimed to analyze antibiotic resistance genes and multilocus sequence typing (MLST) of P. aeruginosa strains isolated from burn patients in Shahid Motahari hospital in Tehran, Iran.Altogether 63 P. aeruginosa isolates were characterized in this study. Antibiotic susceptibility testing was performed by disc diffusion method. PCR was performed to determine the frequency of resistance genes. The expression rates of mexB, mexY genes were evaluated by Real-Time PCR. Genotyping of isolates was performed by MLST analysis. All isolates were MDR in this study. The highest resistance was detected against gentamicin, tobramycin, and cefoxitin (100%), while all isolates were susceptible to colistin. Altogether 14 resistance profiles were determined, and profile 1 included more than 50% of the isolates with the highest resistance. In this study blaampC, blaVIM-2, blaOXA-10, and aac(6')-Ib resistance genes were detected in all isolates. The expression levels of mexB and mexY genes were upregulated in 66.6 and 88.8% of MDR isolates, respectively. Overexpression of both genes was detected in 55.5% of the isolates.MLST analysis revealed five sequence types (STs), including ST235, ST664, ST532, ST2637, and ST230, which showed a significant relationship with antibiotic resistance profiles. The present study indicates an increase in antibiotic resistance against different antibiotic families among P. aeruginosa isolates. We describe the circulation of globally distributed STs among hospitalized patients, and we report ST235 as the most common MDR clone in our study.