Emergence of fluoroquinolone-resistant Escherichia coli in swine poses concerns for managing antimicrobial resistance. This study compared antimicrobial resistance profiles, molecular resistance determinants, and genetic relatedness of fluoroquinolone-resistant E. coli isolated from integrated and conventional swine farms in South Korea. A total of 130 E. coli isolates were obtained from fecal samples collected from 26 farms (13 integrated and 13 conventional farms). Antimicrobial susceptibility testing was performed using disc diffusion and broth microdilution methods. Fluoroquinolone-resistant isolates were analyzed for quinolone resistance-determining region (QRDR) mutations, plasmid-mediated quinolone resistance (PMQR) genes, and multi-locus sequence typing (MLST). Isolates from the conventional farms showed significantly higher resistance rates to several antimicrobials than those from the integrated farms. Among the 58 fluoroquinolone-resistant isolates, QRDR mutations in gyrA and parC were predominant in all samples, with the gyrA S83L/D87N and parC S80I mutations being the most frequently detected. PMQR gene frequencies were comparable in both farm system types and were distributed across multiple sequence types (STs). Fluoroquinolone minimum inhibitory concentrations (MICs) were generally high in both groups; whereas enrofloxacin MICs tended to be higher among the isolates from the conventional farms. MLST-based minimum spanning tree analysis revealed that resistant isolates from both farm types were distributed across multiple STs with limited allelic variation rather than being confined to farm-specific lineages. These findings indicated that, although farm management systems influenced the prevalence of antimicrobial resistance, fluoroquinolone resistance in swine-associated E. coli was maintained within a shared genetic background, emphasizing the need for integrated resistance management strategies beyond antimicrobial usage alone.

To Cite This Article: Do KH, Ryu DH, Kim MG, Choe SJ, Ahn HJ, Go YK, Kim SB, Kim JK, Park YK and Seo KW, 2026. Fluoroquinolone resistance and genetic determinants of Escherichia coli isolated from conventional and integrated swine farms in Korea. Pak Vet J, 46(7): 1802-1809. http://dx.doi.org/10.29261/pakvetj/2026.173