Sampling 58 healthy pigs yielded 176 presumptive isolates, of which 60 were confirmed as S. suis. Multidrug resistance and 65.5% seropositivity were reported despite absence of major classical invasive virulence genes. The findings support One Health surveillance but, with a small sample and only two genomes, are not national prevalence or proof of human transmission.
Key findings
- S. suis was confirmed in 60/176 isolates (34.1%), mainly nasal and tonsillar, with none from blood; seropositivity was 65.5%. Resistance to ceftriaxone, ampicillin, cefepime, clindamycin, and tetracycline and multidrug resistance were common, as were tetracycline/macrolide genes. Serotypes 2/1/2 predominated, major invasive genes were absent, and two genomes were diverse.
Why this matters globally
The findings matter for livestock antimicrobial stewardship, worker safety, and zoonotic surveillance, while requiring S. suis-appropriate susceptibility standards and phenotype-genotype linkage.
Thai researcher contribution
Kasetsart, Chiang Mai, Walailak, and the Upper Northern Veterinary Research and Development Center with Japan integrated microbiology, farm medicine, One Health, serology, and genomics.
Limitations to consider
Fifty-eight pigs and the farm/abattoir mix are not nationally representative. Multiple isolates per pig are non-independent if analyzed as isolates; disc-diffusion breakpoints require clarity. Antibody positivity is not active infection, and two genomes cannot characterize population-wide diversity or mobile elements.