The frequency of genes encoding exotoxin A and exoenzyme S in Pseudomonas aeruginosa strains isolated from burn patients

• Focusing the study in the Burn teaching hospital as the main source of P. aeruginosa resistance strains.
• Investigation of the role of exotoxin A and exoenzyme S on the pathogenesis process of resistant isolates of P. aeruginosa.
• Revising treatment strategies due to increasing of bacterial antibiotic resistance.

BackgroundPseudomonas aeruginosa infections have emerged as a major infectious disease threat in recent decades with infection particularly in immunocompromised hosts. P. aeruginosa possesses several virulence factors with involvement in pathogenesis. The aim of this study was to examine the prevalence of virulence genes of toxA and toxS and to analyze their relation to antimicrobial resistance of the isolates.MethodsIn total 185 clinical isolates of P. aeruginosa were collected from burn patients. Antimicrobial susceptibility testing was done by disk diffusion method. PCR amplification was performed on extracted DNA from the isolates and the presence of encoding genes for exotoxin A (toxA) and exoenzyme S (toxS) were investigated by using specific primers.ResultsIn disk diffusion method, the isolates showed high sensitivity to colistin sulfate (100%) followed by imipenem (41.9%). The most prevalent resistance was seen against ceftazidime (90.5%) and gentamicin (88.5%). Multidrug resistance (MDR) demonstrated in 113 isolates (76.35%). According to PCR amplification, 133 (89.8%) and 127 (85.8%) isolates possessed toxA and toxS genes respectively. The frequencies of genes among MDR strains were 102 (76.6%) for toxA and 98 (77.1%) for toxS. Eighty five MDR isolates possessed both genes (73.9%). The non-MDR strains (23.65%), harbored lower prevalence of simultaneous toxA and toxS genes (26%) compared to MDR strains.ConclusionThe present study established a higher frequency of MDR among P. aeruginosa isolates from burn patients. It was found that the frequency of both toxA &S genes were significantly higher in MDR strains P. aeruginosa strains.