The prevalence of non-aureus staphylococci and mammaliicocci on large Chinese dairy farms.

Non-aureus staphylococci and mammaliicocci (NASM) are currently the most frequently isolated bacteria from subclinical mastitis (SCM) in dairy cows worldwide. There are no targeted reports on dairy cow-derived NASM in China to date. Due to their high prevalence in SCM, NASM can persist in apparently normal milk and enter bulk milk supplies, thereby posing potential food safety hazards. Therefore, to investigate the prevalence of NASM in dairy farms, we collected samples from cows with SCM and clinical mastitis (CM), isolated NASM from apparently normal milk (SCM group) and milk with clinical manifestations (CM group), respectively, and characterized their virulence profiles in the milk of dairy cows with different health statuses.