Prevalence and characterization of ciprofloxacin-resistant <i>Salmonella enterica</i> spp. isolated from food animals during 2010–2023 in South Korea

We isolated 6,561 <i>Salmonella</i> strains from food animals, cattle (<i>n</i> = 217), pigs (<i>n </i>= 1526), chickens (<i>n</i> = 3942), and ducks (<i>n</i> = 876). Isolates were evaluated for antimicrobial sensitivity, mutations in quinolone resistance determination regions (QRDRs), and plasmid-mediated quinolone resistance (PMQR) genes. Clonal relationship and genetic diversity were assessed by multi-locus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE). Overall, 3.1% of isolates exhibited resistance to ciprofloxacin. Commonly identified mutations in QRDRs were S83F, D87N, and D87G in <i>gyrA</i>; T57S and S80I in <i>parC</i>; and L416F in <i>parE</i>. Furthermore, mutations differed by serotypes. In <i>S.</i> Albany, S83F mutation in <i>gyrA</i> and T57S in <i>parC</i> were prevalent, while in <i>S.</i> Kentucky, S83F and D87N in <i>gyrA</i>, T57S and S80I in <i>parC</i>; and in <i>S.</i> Indiana, S83F and D87G in <i>gyrA</i>, T57S and S80R in <i>parC</i>, and L416F in <i>parE</i> were common. Amongst PMQRs, <i>qnrS</i> was mainly observed in <i>S.</i> Albany, <i>aac(6′)-Ib-cr</i> in <i>S.</i> Indiana, and <i>qnrB1</i> in <i>S.</i> Albany. Among STs, ST198 <i>S.</i> Kentucky was predominant, followed by ST292 <i>S.</i> Albany and ST17 <i>S.</i> Indiana. Of 26 pulsotypes, KX1KA1 was mainly identified in <i>S.</i> Kentucky, AX1AA1 in <i>S.</i> Albany, and IX1IA1 in <i>S.</i> Indiana. Taken together, ciprofloxacin-resistant <i>Salmonella</i> can pose health hazards to humans and other animals.