spp. associated with subclinical bovine mastitis in central and northeast provinces of Thailand.

Background: spp. are major cause of bovine mastitis (BM) worldwide leading to economic damage to dairy farms and public health threat. Recently, a newly emerged has been found as a human and animal pathogen. Molecular characteristics, virulence and antibiotic resistant phenotypes of bacteria causing BM in Thailand are rare. This study aimed to investigated spp. associated with subclinical bovine mastitis (SCM) in Thailand.

Methods: Milk samples were collected from 224 cows of 52 dairy herds in four central and northeast provinces. Total somatic cell counts (SCC) and California mastitis test (CMT) were used to identify SCM cows. Milk samples were cultured for spp. Coagulase-positive isolates were subjected to pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Organisms suspected as were verified by detecting nonribosomal peptide synthetase gene. All isolates were checked for antibiograms and the presence of various virulence genes.

Results: From the 224 milk samples of 224 cows, 132 (59%) were positive for SCM by SCC and CMT and 229 staphylococcal isolates were recovered. They were 32 coagulase-positive (24 and eight ) and 197 coagulase-negative. PFGE of the and revealed 11 clusters and a non-typeable pattern. MLST of representatives of the 11 PFGE clusters, three PFGE non-typeable isolates from different locations and showed 12 sequence types. The eight isolates belonged to ST1223 (three isolates), ST2250 (two isolates), and ST2793 (two isolates). The antimicrobial tests identified 11 (46%) methicillin-resistant and 25 (13%) methicillin-resistant coagulase-negative isolates, while seven were methicillin-susceptible and one isolate was methicillin-resistant. All of the 229 isolates were multiply resistant to other antibiotics. The most prevalent virulence genes of the 24 isolates were , and (X and IgG-binding region) (100%), (96%), (96%) and (79%). Six isolates carried one enterotoxin gene each and other virulence genes including and , indicating their pathogenic potential.

Conclusion And Perspective: This is the first report on the from cow milk samples with SCM. Data on the molecular characteristics, virulence genes and antibiograms of the spp. obtained from the present study showed a wide spread and increasing trend of methicillin-resistance and multiple resistance to other antibiotics. This suggests that the "One Health" practice should be nurtured, not only at the dairy farm level, but also at the national or even the international levels through cooperation of different sectors (dairy farmers, veterinarians, medical and public health personnel and scientists) in order to effectively combat and control the spread of these pathogens.