Low Prevalence of Streptococcus Suis and Bacterial Contamination in Raw Pork Products From Fresh Markets in Nakhon Ratchasima, Thailand

Streptococcus suis is a zoonotic pathogen associated with severe human infections, particularly in regions where consumption of raw pork is common. This study aimed to investigate the prevalence of S. suis in raw pork products sold in fresh markets in Mueang District, Nakhon Ratchasima Province, Thailand. A total of 113 raw pork samples were collected from four fresh markets and analyzed microbiologically. S. suis was detected in one liver sample, corresponding to a low overall prevalence of 0.88%. Nonetheless, microbial growth was observed in 55.75% (63/113) of samples, yielding 68 isolates. Liver and loin samples demonstrated the greatest microbial diversity and frequency of contamination. Biochemical tests of the S. suis isolate revealed characteristic features including alpha-hemolytic activity, catalase negativity, and selective sugar fermentation, which were consistent with known profiles of the species. Identification was confirmed using Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS) and detected species included Enterococcus faecalis, Enterococcus casseliflavus, Staphylococcus hominis, and Staphylococcus saprophyticus. Antimicrobial susceptibility testing showed that the isolate was susceptible to beta-lactams, quinolones, chloramphenicol, tigecycline, linezolid, trimethoprim/sulfamethoxazole, and vancomycin, while resistance was observed to macrolides, lincosamides, and tetracycline. Multiplex PCR confirmed the isolate as S. suis  serotype 2, and multilocus sequence typing (MLST) further identified it as sequence type 104 (ST104). These findings indicate the microbial contamination risk associated with raw pork sold at fresh markets and emphasize the importance of routine surveillance and improved hygiene practices.