Whole-genome analysis of 138 S. uberis isolates from three Thai dairy herds identified 42 core-genome sequence types and abundant mobile elements. The herd with the highest antimicrobial-resistance gene prevalence had a recombination-to-mutation ratio of 4.42 and more AMR-associated mobile elements. Some prophages were over 99% similar to phages infecting other genera, providing genomic signals of ecological genetic exchange.
Key findings
- The study found 42 cgSTs, plasmid-associated genes in 81.1% of isolates, prophages in 67.4% and insertion sequences in 26.1%. Herd A had the longest recombined fragments but very low recombination frequency and ratio. Herd B, with the highest AMR-gene prevalence, had R/θ=4.42 and more AMR-associated elements. Herd C shared one core genome and AMR profile but carried diverse prophages; some were over 99% similar to phages from other genera.
Why this matters globally
S. uberis mastitis affects animal welfare, antimicrobial use, milk quality and costs worldwide. Genomic surveillance may distinguish transmission from recurrence and track resistance elements, but it must be integrated with epidemiology and functional evidence.
Thai researcher contribution
Chiang Mai University analysed isolates from three Thai dairy herds with Wageningen and Nagoya collaborators. Thai farms are the core dataset, not merely an author-affiliation link.
Limitations to consider
Three herds cannot represent all Thai dairy systems. Observational genomics does not establish direction or timing of transfer. Over 99% prophage similarity suggests possibility but does not prove active cross-genus exchange. AMR genes do not equal phenotype, and antimicrobial-use, animal, environmental and longitudinal data are needed.