• Nour Amirmozafari, Jalil Fallah Mehrabadi, and Alireza Habibi.
• Microbiology Department, School of Medicine, Iran University of Medical Sciences, Tehran, Iran.
• Arch Iran Med. 2016 May 1; 19 (5): 353-8.

IntroductionPseudomonas aeruginosa is a gram-negative and opportunistic bacterium that causes opportunistic infections in immunosuppressed patients. The main purpose of this study was to investigate the association between exotoxin A and exoenzyme S production with antibiotic resistance patterns.MethodsThe toxA and exoS genes were detected in 102 clinical isolates by PCR. Antibiotic susceptibility tests were performed by disk diffusion method (Kirby Bauer). The Chi-square and Fisher's test were used for evaluation of the association between "toxins and infections source" and "toxins and antibiotic resistance" respectively.ResultsFrequency of toxA+ and exoS+ strains was 81% and 61%, respectively. The association between drug resistance and toxA+ genotype was significant for all antibiotics tested (P < 0.05) except aztreonam; however, no significant association was observed between drug resistance and exoS gene (P > 0.05).ConclusionsHigh frequency of toxA+ resistant strains isolated from inpatients and significant association between the toxin and drug resistance in more antibiotics, reinforces possible role of exotoxin A as an extracellular protein in the regulation of drug resistance genes. The results may be further verified by Southern blot analysis of toxA and exoS gene expression and elucidation of the mechanism of antibiotic resistance.

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