{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,10]],"date-time":"2026-08-10T11:32:05Z","timestamp":1786361525007,"version":"build-2736575974"},"reference-count":29,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2026,8,10]],"date-time":"2026-08-10T00:00:00Z","timestamp":1786320000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Veterinary Research Institute, Ministry of Agriculture, Taiwan","award":["113AS-5.1.1\u2013VI-04"],"award-info":[{"award-number":["113AS-5.1.1\u2013VI-04"]}]},{"name":"Veterinary Research Institute, Ministry of Agriculture, Taiwan","award":["114AS-5.1.1-VI-04"],"award-info":[{"award-number":["114AS-5.1.1-VI-04"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Antibiotics"],"abstract":"<jats:p>Background: The global spread of antimicrobial resistance in Escherichia coli (E. coli) from food-producing animals is a critical concern within the One Health framework, particularly because of the potential transmission of clinically relevant resistance determinants across the animal\u2013environment\u2013human interface. Although extended-spectrum \u03b2-lactamase (ESBL)-producing E. coli strains have been widely characterized, the genomic mechanisms underlying resistance to the last-resort and critically important antimicrobials colistin and fluoroquinolones remain incompletely understood in animal-associated populations. This study characterized these resistance mechanisms in multidrug-resistant (MDR) E. coli from diseased food-producing animals. Methods: We used whole-genome sequencing (WGS) to characterize 77 MDR E. coli isolates from diseased livestock and poultry in Taiwan and analyzed the underlying resistance mechanisms and their co-occurrence. Results: Plasmid-mediated colistin resistance genes, including mcr-1.1, mcr-3.1, and mcr-3.5, were identified alongside chromosomal mutations, such as pmrB substitutions, indicating multiple evolutionary pathways to colistin resistance. Fluoroquinolone resistance was driven by both chromosomal mutations in quinolone resistance-determining regions and plasmid-mediated quinolone resistance genes, including qnr variants and aac(6\u2032)-Ib-cr. Notably, the frequent co-occurrence of resistance determinants targeting multiple antimicrobial classes suggests the presence of mobile genetic elements facilitating horizontal gene transfer. Conclusions: Although a subset of isolates overlapped with those reported in our previous ESBL-focused study, the present work presents a comprehensive genomic dissection of resistance mechanisms beyond \u03b2-lactamases. The convergence of colistin, fluoroquinolone, and ESBL-associated resistance determinants within individual isolates highlights the potential role of food-producing animals as reservoirs of multidrug resistance, with potential implications for cross-sectoral transmission. These findings underscore the importance of integrated surveillance strategies addressing potential zoonotic transmission under the One Health framework.<\/jats:p>","DOI":"10.3390\/antibiotics15080765","type":"journal-article","created":{"date-parts":[[2026,8,10]],"date-time":"2026-08-10T10:23:50Z","timestamp":1786357430000},"page":"765","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Genomic Characterization of Colistin and Fluoroquinolone Resistance in Multidrug-Resistant Escherichia coli from Diseased Food-Producing Animals in Taiwan"],"prefix":"10.3390","volume":"15","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-2395-6609","authenticated-orcid":false,"given":"Nan-Ling","family":"Kuan","sequence":"first","affiliation":[{"name":"Biology Division, Veterinary Research Institute, Ministry of Agriculture, Tamsui, New Taipei City 251018, Taiwan"},{"name":"Department of Veterinary Medicine, School of Veterinary Medicine, National Taiwan University, Taipei 106319, Taiwan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kuang-Sheng","family":"Yeh","sequence":"additional","affiliation":[{"name":"Department of Veterinary Medicine, School of Veterinary Medicine, National Taiwan University, Taipei 106319, Taiwan"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,8,10]]},"reference":[{"key":"ref_1","unstructured":"WHO (2018). 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