Characteristics of Staphylococcus aureus Isolates from Raw Milk

Staphylococcus aureus has raised great health concerns worldwide. In this work, with the traditional culture-based methods, totally 70 bacterial isolates on Barid-Parker medium from raw milk samples are collected from 181 healthy cows in a dairy farm located in Northern China. With comparative sequence analysis of 16S rDNA genes, 18 isolates were identified as S. aureus. One isolate was resistant to cefoxitin and tentatively considered as a methicillin-resistant S. aureus ( MRSA) strain. Spa typing was performed to discriminate the strains. Four spa types were determined, including t3104 in 12 strains, t267 in 3 strains, t521 in 2 strains, and t528 in strain Z1584. The type t11557 was a new spa type discovered in this work and its repeats succession was 07-12-21-13-34-34-33-13. Our work suggested that the prevalence of MARA strains was quite low in fresh raw milk produced in the dairy farm located in Northern China.