Original Article Presence of Qnr genes related to resistance to quinolones, first-, second-, and third-generation in diarrheagenic Escherichia coli Abbas Mokhtari-Farsani a,b , Abbas Doosti b, * , Zahra Mohammadalipour b a Young Researchers and Elite Club, Shahrekord Branch, Islamic Azad University, Shahrekord, Iran b Biotechnology Research Center, Islamic Azad University, Shahrekord Branch, Postal box: 166, Shahrekord, Iran 1. Introduction Diarrheal diseases remain a public health problem worldwide with more than two million deaths occurring each year, especially in developing countries. 1 The bacterial pathogens responsible for diarrheal disease include diarrheagenic Escherichia coli (DEC), Yersinia, Shigella, Salmonella, Campylobac- ter, Aeromonas, etc. 2 Six major classes of DEC including enterotoxigenic E. coli, enteroinvasive E. coli, enteropathogenic E. coli, enteroaggrega- tive E. coli, enterohemorrhagic E. coli and diffuse adhering E. coli are the most common microorganisms that cause diarrheal illness. 3,4 These bacteria are the major target of antimicrobial j o u r n a l o f p a t i e n t s a f e t y & i n f e c t i o n c o n t r o l x x x ( 2 0 1 6 ) x x x – x x x a r t i c l e i n f o Article history: Received 17 October 2015 Accepted 16 December 2015 Available online xxx Keywords: Antibiotic resistance Diarrhea Escherichia coli Plasmid-mediated quinolone- resistance Qnr genes a b s t r a c t Background: Resistance genes transferred by plasmids are important factors that can con- tribute to the occurrence of quinolone resistance, specifically in Escherichia coli strains. Methods: A total number of 117 diarrheagenic E. coli strains were tested for the resistance to nalidixic acid, ofloxacin, ciprofloxacin and levofloxacin, and for the presence of qnrA, qnrB and qnrS genes determinants by polymerase chain reaction. Antibiotic susceptibility test was performed using the Clinical and Laboratory Standard Institute standard method. Results: The highest resistance belonged to the nalidixic acid (52.14%) and the least resistance to levofloxacin (37.61%). In this study among a total of 117 samples, 23 (19.66%) strains were susceptible to all the studied antibiotics. Among the remainder 94 (80.34%) samples resistant to at least one quinolone, three genes including qnrA, qnrB, and qnrS were present in 19.15%, 88.30%, and 78.72% isolates, respectively. Furthermore, 51.06% of strains had A, B+, and S+ pattern that seems to have a significant association (P < 0.001) with resistance to quinolones. Conclusions: The results of present study show the presence of a high frequency of qnr genes in E. coli strains resistant to quinolones in clinical samples from southwest of Iran. In addition, this study approved that plasmid-mediated quinolone resistance (PMQR) is a possible mech- anism among the quinolones-resistant E. coli isolated from patients with diarrhea in the study, and also qnrB and qnrS genes seem to be more important in resistance to quinolones. # 2015 Hospital Infection Society India. Published by Elsevier, a division of Reed Elsevier India, Pvt. Ltd. All rights reserved. * Corresponding author. Tel.: +98 38 13361001; fax: +98 38 13361001. E-mail address: geneticsshki@yahoo.com (A. Doosti). JPSIC-51; No. of Pages 5 Please cite this article in press as: Mokhtari-Farsani A, et al. Presence of Qnr genes related to resistance to quinolones, first-, second-, and third-generation in diarrheagenic Escherichia coli, J Patient Saf Infect Control. (2015), http://dx.doi.org/10.1016/j.jpsic.2015.12.002 Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/jpsic http://dx.doi.org/10.1016/j.jpsic.2015.12.002 2214-207X/# 2015 Hospital Infection Society India. Published by Elsevier, a division of Reed Elsevier India, Pvt. Ltd. All rights reserved. Downloaded from http://www.elearnica.ir