Prevalence and Multidrug-Resistance Salmonella in Swine Production Chain in a Central Province, Thailand.

Salmonella causes foodborne disease outbreaks worldwide and raises considerable concerns about public health and economic losses. To determine prevalence, serovar, antimicrobial resistance (AMR) patterns, and extended-spectrum beta-lactamase (ESBL) genes, the present cross-sectional study collected a total of 418 fecal, carcass (three slaughterhouses), pork and cutting board (four markets) samples from a province in central Thailand in 2017 and 2018. Results showed that 65.1% (272/418) of samples were positive for Salmonella. The percentage of Salmonella positive samples from markets (88.8%; 158/178) was significantly higher than those from slaughterhouses (47.5%; 114/240) ( P<0.05 ). In total, 1,030 isolates were identified; of these, 409 were assigned to 45 serovars with S. Rissen (20%; 82/409) being the most common. New serovars of Thai isolates, S. Cannstatt and S. Braubach, were identified in market and slaughterhouse samples, respectively. AMR of Salmonella isolates showed that 73.9% (133/180) of 19 different serovars exhibited multidrug resistance (MDR). Screening for ESBL production showed that 10.3% (41/399) of isolates were ESBL positive. ESBL-producing Salmonella isolates in market samples (75.6%; 31/41) were significantly higher than those in slaughterhouse samples (24.4%; 10/41) ( P<0.05 ). In market samples, 77.4% (24/31) were isolated from pork and 22.6% (7/31) from cutting boards. Nine ESBL-producing isolates carried single type ESBL genes bla TEM (9.8%; 4/41) or bla CTX-M (12.2%; 5/41), while 11 (26.8%) carried both bla TEM and bla CTX-M . No ESBL-producing Salmonella isolate carried the gene bla SHV . Results suggest that pigs, their flesh, and cutting boards could be reservoirs for widespread MDR, ESBL-producing Salmonella outbreak across the food chain.