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Mechanisms of quinolone resistance in Escherichia coli isolated from companion animals, pet-owners, and non-pet-owners
Yeon Soo Chung1, Yoon Sung Hu1, Sook Shin1, Suk Kyung Lim2, Soo Jin Yang3, Yong Ho Park1, Kun Taek Park1,*
1Department of Veterinary Microbiology, College of Veterinary Medicine, BK21 Plus Program for Veterinary Science and Research Institute for Veterinary Science, Seoul National University, Seoul 151-742, Korea
2Animal and Plant Quarantine Agency (QIA), Anyang 430-757, Korea
3Department of Animal Science and Technology, College of Biotechnology and Natural Resource, Chung-Ang University, Anseong 456-756, Korea
Correspondence to: Tel: +82-2-880-4175; Fax: +82-2-871-7524; E-mail: magic007@snu.ac.kr
Received: November 14, 2016; Revised: February 8, 2017; Accepted: February 22, 2017; Published online: April 6, 2017.
The present study investigated the prevalence and the mechanisms of fluoroquinolone (FQ)/ quinolone (Q) resistance in Escherichia coli isolates from companion animals, pet-owners, and non-pet owners. A total of 63 E. coli isolates were collected from 104 anal swab samples; 27 nalidixic acid (NA)-resistant isolates were identified. Of these, 10 showed ciprofloxacin (CIP) resistance. Plasmid-mediated Q resistance gene was detected in an isolate. Increased efflux pump activity, as measured by organic solvent tolerance assay, was detected in 18 isolates (66.7%), but this was not correlated with the increased minimum inhibitory concentration (MIC). Target gene mutations in Q resistance-determining regions (QRDRs) were the main cause of (F)Q resistance in E. coli. Point mutations in QRDRs were detected in all NA-resistant isolates, and the number of mutations was strongly correlated with increased MIC (R = 0.878 for NA and 0.954 for CIP). All CIP-resistant isolates (n = 10) had double mutations in the gyrA gene, with additional mutations in both parC and parE genes. Interestingly, (F)Q resistance mechanisms observed in isolates from companion animals were the same as those in humans. Therefore, prudent use of (F)Q in veterinary medicine is warranted to prevent the dissemination of (F)Q-resistant bacteria from animals to humans.
Keywords: Quinolone; Fluoroquinolone; Antimicrobial resistance; Escherichia coli; Companion animal.

© 2017 The Korean Society of Veterinary Science.