MOJDEH HAKEMI-VALA¹, FATEMEH BAGHERY BEJESTANY², ALI HASHEMI¹, PARVIZ KAVAKEB³, RAHELE MOMTAHENI², SAIIDEH RAHIMIGOLLO<sup>2

1</sup>Department of microbiology, medical school, Shahid Beheshti university of medical sciences Tehran-Iran, ²Pharmaceutical sciences branch, Islamic Azad University Tehran-Iran, ³Sina hospital, Tehran university of medical sciences Tehran-Iran

Background: Among burn wounds infection agents the role of P.aeruginosa is important because of their high resistant to common antibiotics[1]. So the aim of this study was evaluation the co-existence of oprD porin and MexAB-oprM efflux pump genes among P.aeruginosa isolates from burn patients.

Materials and methods: During 2013-14, 80 P.aeruginosa isolates were identified and collected randomly from burnt patients who admitted to Burn unit of Motahari hospital. The antimicrobial sensitivity test (AST) by Kirby-Bauer method and Minimum inhibitory concentration (MIC) of imipenem by E-test was determined based on the CLSI 2014 protocol[2]. The co-existence of oprD and Mex-AB-oprM genes was evaluated by PCR and further sequencing.

Results: Based on the results of AST, resistant to tested antibiotics was as follow; piperacillin 88.7%, ticarcillin 90%, piperacillin-tazobactam 81.3%, ceftazidime100%,cefepime 67.58%, azteronam 88.8%, imipenem 53.8%, meropenem 77%, gentamicin 68%, tobromycin 86.3%, ciprofloxacin 86.3%. By E-test, resistant isolates showed MIC≥ 8µg/mL for imipenem. Simultaneous existence of oprD and Mex-AB-oprM genes were detected in 90.2% and 67.5% of isolates, respectively. Gene submission was done for oprD genes with accession No; KJ154062-3 and is in process for Mex-AB-oprM gene. New mutations in OprD were detected after alignment and comparison with P.aeruginosa PAO1 as follow; T103S, K115T, F170L, P186G and V189T.Among detected mutations, changes of K to T (related to change of lysine to thereonine) and V to T (related to change of valine to thereonine) seems more important because of change in a nonpolar to polar acid amine.

Conclusion: by the results of this study, sum of the changes of oprD porin and Mex-AB-oprM efflux pump, multidrug resistant (MDR) P.aeruginosa isolates was emerged. The importance of MDR isolates are related to their high mortality rate especially in immune deficient burn patients. Such changes in oprD gene not only can effect on the structural shape but also on the functional property of the OprD protein which is important in drug delivery.

Key words: oprD, Pseudomonas aeruginosa, Mex-AB-oprM