Antibiotic resistance, sequence typing, and virulence gene profiles of Salmonella enterica isolated from the broiler production chain in southern Thailand.

Salmonella is a major foodborne pathogen from poultry farms and potentially transferred to meat products during processing in slaughterhouses or transportation to wet markets. From a total of 351 samples, only 73 samples (20.8 %) collected from broiler farms, slaughterhouses, and chicken meat stalls at a wet market, which were selected independently within the same province, were positive for Salmonella. Fifty-six Salmonella isolates were evaluated for the presence of nine known virulence genes (sipB, prgH, spaN, orgA, tolC, sitC, sifA, cdtB, and sopB) and their antibiotic resistance profiles. Pattern II (cdtB negative) represented the most predominant pattern found in 23 Salmonella isolates. The most common antibiotic resistance profile was AMP-TE-CIP-NA, found in 10 isolates from all sources. The relationship of subtypes of Salmonella spp. isolated, analyzed by multilocus sequence typing (MLST), revealed twelve sequence types (STs). The most frequently detected sequence type was ST198 (26.8 %), identified in S. Kentucky. In this study, ST198 was identified in six multidrug resistance (MDR) profiles from all sources and was associated with ampicillin and ciprofloxacin resistance. Overall, our study indicated the potential public health benefits of monitoring STs and antibiotic resistance phenotypes to track the spread of MDR in Salmonella isolates from specific sources, including within the broiler value chain.