The goal of this doctoral dissertation is to describe host-pathogen interactions between heifers and ecologically diverse CNS species and strains, in order to explain the dichotomy between host-adapted and environmental CNS. In light of the apparent increased milk yield in CNS-infected cows, the role of prolactin was also examined, as a potential autocrine lactation hormone and immunomodulatory factor.
Coagulase-negative staphylococci (CNS) are one of the most common causative agents of subclinical mastitis in dairy cattle. Ecologically speaking, CNS can be divided into ‘host-adapted’ and ‘environmental’ species. Host-adapted species, such as Staphylococcus chromogenes, are mainly found in the milk or on the cow’s body. Environmental species, like Staphylococcus fleurettii, on the other hand, mostly occur in the immediate surroundings of the cow and rarely in milk. Why some species thrive in the mammary gland, as opposed to other body sites or the surrounding environment is not entirely clear. Little is known about the host response of dairy cattle to different CNS species and strains. Surprisingly, there are even a number of observational studies showing that CNS-infected cows, against all odds, produce more milk than their non-infected herd mates.
Eight healthy Holstein heifers in mid-lactation were inoculated with three CNS field strains: one particular environmental S. fleurettii strain originating from sawdust and two representative host-adapted S. chromogenes strains. One of those strains (S. chromoge
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