PURPOSE:To determine the genetic diversity of MDR P. aeruginosa strains isolated from burn and wound infections in Ahvaz, Iran, by ERIC-PCR. METHODS:From total 99 strains of P. aeruginosa defined as MDR by using drug susceptibility testing, 66 were subjected to ERIC-PCR analysis, comprises 53 strains isolated from burn infection, and 13 randomly selected strains from wound infection with higher resistance to combinations of more numbers of drugs. RESULTS:Eight clusters (I to VIII), and 50 single clones were generated for tested MDR isolates analyzed by ERIC-PCR. The high heterogeneity was observed among the isolates from burn infections including 16 isolates which were categorized in eight clusters and 37 single clones. The isolates in clusters II, III, VI, VIII showed 100% similarity. CONCLUSIONS:The high level of genotypic heterogeneity in P. aeruginosa strains demonstrated no genetic correlation between them. Extremely high drug resistance in isolates from burn, suggests that efficient control measures and proper antibiotic policy should be observed.

Background: The emergence of highly drug resistant Pseudomonas aeruginosa in burn wounds is becoming a challenging problem for infection control programs. Today, it has been shown that antibiotic resistance in P. aeruginosa is the result of synergism between membrane permeability and multidrug resistance (MDR) efflux pumps. Objectives: The aim of this study was to investigate MDR and pan-drug resistance (PDR) in P. aeruginosa and detection of the presence of efflux pump MexAB genes by the polymerase chain reaction (PCR) technique. Materials and Methods: One-hundred and fifty P. aeruginosa were isolated from burn and wound infections. The isolates were confirmed using conventional culture and biochemical tests. Antibiotic resistance was evaluated using agar disk diffusion and broth micro dilution tests. For detection of efflux pump MexAB genes, the PCR technique with subsequent sequencing was used. Results: In total, 99 strains (66%) were MDR and one strain (0.667%) was PDR as detected by traditional susceptibility tests. The MDR isolates belonged to 53 burn (70.66%) and 46 wound (61.33%) infections. The PDR was only seen in one isolate from a burn strain (1.33%). The PCR technique revealed that all the 99 MDR strains and one PDR strain, contained MexA and MexB genes, representing an exhibitive intrinsic existence of these genes in MDR and PDR of P. aeruginosa. Conclusions: This study represented an increasing rate of MDR P. aeruginosa in burn and wound samples. Efflux MexAB genes were detected in all MDR and PDR strains. The P. aeruginosa strain isolated from burn cases showed higher drug resistance and PDR resistance was only noted in a burn sample.