Fluoroquinolone resistance in non-typhoidal isolated from slaughtered pigs in Thailand.

The emergence and spread of non-typhoidal (NTS) serovars resistant to fluoroquinolones and third- and higher-generation cephalosporins is a matter of great concern. Antimicrobial-resistant NTS is increasingly being discovered in humans, animals, food animals, food products, and agricultural environments. Pigs are considered a major reservoir of antimicrobial-resistant spp. Fluoroquinolone-resistant spp. warrant further surveillance and characterization for a better understanding of the bacteria isolated from animals. NTS isolated from pork from slaughterhouses across Thailand were characterized in terms of their serovars; resistance to fluoroquinolones, third-generation cephalosporins, and carbapenems; and antimicrobial resistance genes. A total of 387 NTS isolates, collected from slaughtered pigs in ten provinces across Thailand between 2014 and 2015, were characterized based on their serovars, antimicrobial resistance genes, and susceptibility to fluoroquinolones, third-generation cephalosporins, and carbapenems. Among all NTS isolates, serovar Rissen was predominant. Antimicrobial resistance was exhibited in 93/387 isolates (24 %). Although 24 (6.2 %) isolates were susceptible to all the tested antimicrobials, they were found to possess β-lactamase genes, such as , , or . Mobilized colistin-resistant genes () and resistance to colistin were not observed in any tested isolate. Carbapenem resistance was detected in ten isolates (10.7 %); however, , , , and were not present. Among the 93 antimicrobial-resistant isolates, 87.1 % showed fluoroquinolone resistance with the quinolone resistance gene () combined with topoisomerase genes (T57S) or (S83E/Y and D124E/G) substitutions, or topoisomerase gene substitutions alone. We found high fluoroquinolone resistance rates among the NTS isolates from pigs from slaughterhouses. The fluoroquinolone resistance mechanism in NTS was associated with the combination of and substitutions in , or both. To prevent the transmission of antimicrobial-resistant NTS between animals and humans, continuous monitoring, surveillance, and regulation of in the pork supply chain are pivotal.