Multidrug resistance and integron carriage in clinical isolates of Pseudomonas aeruginosa in Tehran, Iran

Background/aim: Pseudomonas aeruginosa is the cause of 10% of hospital-acquired infections. The organisms are often multidrug-resistant, mediated mostly by antibiotic-resistant integrons. The aim of this research was to study integron carriage and its association with multidrug resistance in burn and nonburn clinical isolates of P. aeruginosa. Materials and methods: A total of 112 P. aeruginosa clinical isolates were collected from the Motahari and Shohadaye Tajrish hospitals in Tehran between July and December 2011. Antibiotic susceptibility to 13 antibiotics was determined by disk diffusion. Detection of integron classes 1 and 2 and amplifications of internal variable regions (IVRs) of class 1 integrons were carried out by PCR and specific primers. Results: Among the 112 isolates, 77 were from burn patients and 35 were nonburn isolates. Multidrug resistance and class 1 integron carriage were both significantly higher in the burn isolates compared to the nonburn strains (97.4% vs. 22.8% and 82.3% vs. 17.7%, respectively). Class 2 integron (2.7%) was only present in the burn isolates. Amplification of IVRs of class 1 integrons revealed 3 different fragment arrays. Conclusion: The significant association between multidrug resistance and integron carriage among P. aeruginosa burn isolates suggests a dissemination of resistance determinants by horizontal gene transfer.