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P3-145 The Mechanisms of Fluoroquinolone Resistance in Escherichia coli from Swine Feces

Wednesday, August 3, 2016
America's Center - St. Louis
Yoon Sung Hu, Seoul National University, Seoul, Korea, The Republic of
Yeon Soo Chung, Seoul National University, Seoul, Korea, The Republic of
Dae Ho Kim, Seoul National University, Seoul, Korea, The Republic of
Young Kyung Park, Seoul National University, Seoul, Korea, The Republic of
Sook Shin, Seoul National University, Seoul, Korea, The Republic of
Kun Taek Park, Seoul National University, Seoul, Korea, The Republic of
Yong Ho Park, Seoul National University, Seoul, Korea, The Republic of
Introduction: Fluoroquinolones (FQ) are potent synthetic antimicrobials against most Enterobacteriaceae, including E. coli, and these agents have been extensively used in animal industry, as feed additives, as well as in veterinary and human medicine. Consequently, FQ resistance has rapidly increased worldwide posing a serious threat to the public health.

Purpose: The study was designed to investigate the frequency and mechanisms of FQ resistance in E. coli from swine industry. The 3 major FQ resistance mechanisms investigated in the current study were target mutations in quinolone resistance determining regions (QRDR), presence of plasmid-mediated quinolone resistance (PMQR) genes, and increase in efflux pump activity.

Methods: For 171 E. coli isolates (collected from 237 swine fecal samples), ciprofloxacin (CIP) resistances were screened by standard disk diffusion method and minimum inhibitory concentrations (MICs) were determined by broth microdilution method. PCR and sequencing analysis were used to confirm target mutations in QRDRs and the presence of PMQR genes. Organic solvent tolerance (OST) assay was used to measure efflux pump activity in the isolates.

Results: Of 171 E. coli isolates, 59 (59/171; 34.5%) showed resistance to CIP (MICs: 4 μg/ml - 256 μg/ml). Of 59 CIP-resistant isolates, 58 (98.3%) had single (n=1, 1.7%) or multiple amino acid substitutions (n=57, 96.6%) in QRDRs, whereas 9 isolates (15.3%) had PMQR genes; qepA (n=1, 1.7%), qnrS, (n=7, 11.9%), aac-(6’)-Ib-cr (n=1, 1.7%), respectively. The OST assay is currently under progress.

Significance: FQ resistance mechanisms observed in animal isolates are identical to those found in human isolates. Therefore, use of FQ in animal industry should be carefully managed to prevent the dissemination of FQ-resistant bacteria from animals to humans.

Back to: Poster Session 3 – Antimicrobials, Laboratory and Detection Methods, Microbial Food Spoilage, Modeling and Risk Assessment, Retail and Food Service Safety and Sanitation
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