Microarray-Based Serotyping and Molecular Characterization of Virulence and Antimicrobial Resistance of Salmonella enterica from Swine Meat Samples in Abattoirs and Wet Markets of Metro Manila, Philippines

Salmonella is a globally prevalent and diverse group of pathogenic bacteria that reside in food animals, such as swine. They possess transmissible antimicrobial resistance (AMR) and virulence factors, causing outbreaks with varying disease outcomes. This study identified and characterized 110 Salmonella enterica isolates from swine meat in abattoirs and wet markets of Metro Manila, Philippines. Thirteen different S. enterica serovars were identified using the Check & Trace microarray platform. The most prevalent were Rissen, Typhimurium 1, 4, [5], 12:i:-, Anatum, and Derby. This study is also the first to report serovar Soerenga in the Philippines and Asia. A high prevalence of virulence genes was observed, namely, hilA (75.45%), avrA (73.64%), mgtC (72.73%), pipB (66.36%), sseC (58.18%), and spi4R (53.64%), with no plasmid-borne spvC and spvR. A high prevalence of blaTEM (44.55%) was also observed, consistent with the phenotypic AMR profiles. Additionally, 14.81% of the isolates exhibited multidrug resistance. Statistical associations and predictions were also found among virulence genes, serovars, and location types, which highlight implications of Salmonella contamination and serovar variations. These findings suggest the need for continuous surveillance of Salmonella, especially for emerging or rare serovars, the deeper investigation of virulence and AMR mechanisms, and improved regulation and sanitation throughout food animal industries.