Bovine mastitis is the costliest infectious disease on US dairies and is a primary focus of agricultural research and extension work. Nearly all cases of mastitis are bacterial in origin and intramammary antibiotics are the most common treatment. Considering the immediate risks associated with antibiotics: reduced effectiveness due to resistant bacteria, food safety issues, and negative environmental impacts, alternative strategies to reduce the incidence and/or effectively treat mastitis are needed. A promising class of intramammary prophylactics/therapies is based on natural bacterial-bacterial interactions in the udder. Evidence suggests that the presence of Non-aureus Staphylococcus (NAS) in the udder or on the teat end protects against severe intramammary infection with major mastitis pathogens including Staphylococcus (S.) aureus, Streptococcus (S.) uberis and Escherichia (E.) coli. This “gatekeeping”  effect, while not well-understood, has been attributed to antimicrobial substances secreted by NAS. The activity of NAS-secreted factors has the potential to be leveraged to reduce the incidence and/or severity of bovine mastitis and the associated risks. 

Invitro testing of a broad range of field strains of NAS and major mastitis pathogens from known dairy herds for experimental use will fine tune what is known about NAS-major pathogen interactions and their farm-specific contributions. For example, in a herd with a low incidence of S. aureus mastitis, the effects of a particular NAS species and strains on major pathogens may be quite different from the effects of NAS on major pathogens in a herd with a high prevalence of S. aureus infection. The most routinely diagnosed NAS in submissions to the Cornell University Animal Health Diagnostic Center (AHDC) are S. chromogenes, S. xylosus, S. simulans and S. sciur. Isolates of these species, along with major mastitis pathogens from the same dairies will allow us to perform in vitro experiments designed to determine and characterize the inhibitory effects of specific NAS on individual major pathogens and highlight differences in strains for farms that have lower versus higher incidences of major pathogens. These functional data will provide the means to experimentally tease apart the mechanisms of inhibition, a necessary step in developing a NAS-based prophylactic/treatment for mastitis. 

This proposal describes the purchase of a plate reader to expand our laboratory's ability to perform invitro bacterial testing and ELISA tests in order to study interactions between mastitis-associated bacterial species and characterize their secretions. The long-term goal of this work is to understand the mechanisms by which NAS-secreted factors inhibit major mastitis pathogens, so they can be leveraged as non-antibiotic strategies for the treatment and prevention of mastitis.