Association of Coagulase Negative Staphylococcal Species and Milk Somatic Cell Count of Cows from the Canadian National Cohort of Dairy Farms

Abstract

Staphylococci are a diverse group of gram-positive cocci that can infect the cow's mammary gland. For the purposes of diagnosing intramammary infection (IMI), staphylococci are classified based on their ability to clot plasma (coagulase test) as either coagulase-positive or coagulase-negative. The most commonly isolated coagulase-positive staphylococci, S. aureus, is considered a major mastitis pathogen. In contrast, coagulase-negative staphylococci (CNS) have historically been classified as minor mastitis pathogens and are rarely, if ever, further differentiated when diagnosing an IMI. The assumption has been that, as a group, CNS cause minor elevations in milk somatic cell count (SCC). However, there has been recent interest in the role of CNS in mammary gland inflammation. The aim of this study was to evaluate the relationship between CNS species and mammary quarter SCC.