Zahra Meshkat - Antimicrobial Resistance Research Center, Mashhad University of Medical Sciences, Mashhad, Iran.
Kiarash Ghazvini - Department of Microbiology and Virology, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
Himen Salimizand - Department of Microbiology, Faculty of Medicine, Kurdistan University of Medical Sciences, Sanandaj, Iran
Yousef Amini - Infectious Diseases and Tropical Medicine Research Center, Zahedan University of Medical Sciences, Zahedan, Iran

Background: Acinetobacter baumannii, as a hospital-acquired pathogen, has become a worldwide problem in recent years. In the current study, resistance to tetracyclines was assessed in isolates from disparate provinces of Iran. Methods: Seven referral centers across six separated provinces were subjected in this study. The minimum inhibitory concentration (MIC) for tetracycline, doxycycline and minocycline and the effect of efflux pump inhibitors (EPIs) were evaluated. Tetracycline resistance determinant genes were assessed by PCR. The clonal relationship of isolates was assessed. Results: Amongst 270 A. baumannii isolates the resistance rate for tetracycline, doxycycline and minocycline were 87.5%, 51.4% and 28%, respectively. The prevalence of tetracycline resistance genes was 99.2, 99.2, and 86.7% for adeB, adeJ and tetB in tetracycline-resistant isolates. tetA (39) was detected in 64.7% and 11.9% of A and B centers, respectively, both from KhorasanRazavi. Few isolates from two separated provinces, 23.5% of C and 2.5% of F centers, showed tetA gene. Efflux pump inhibitors showed a strong effect on 95% of isolates. Rep-PCR determined 122 clones that were divided into 11 clusters. About 43.5% of strains belonged to IC2 and 6.6% of strains were IC1. Clonal complex 2 (CC2) was widespread and is in-circulate in all centers. Conclusion: According to the high rate of resistance, tetracyclines should be cautiously prescribed for treating A. baumannii infections in Iran. Moreover, our results indicated that tetracycline resistance in Iran may is mediated by RND and tetB efflux pumps. tetB appeared to be endemic and other tetracycline resistance determinants were manifested mono-centric in Iran.

Acinetobacterbaumannii, tetracyclines, tetA, tetB, tetM, tetA (39)