IN VITRO GROWTH INHIBITION OF MAJOR MASTITIS PATHOGENS BY STAPHYLOCOCCUS CHROMOGENES ORIGINATING FROM TEAT APICES OF DAIRY HEIFERS

摘要

The significance of coagulase-negative staphylococci (CNS), usually categorized as skin flora opportunists, in both the udder and the teat canal is still not clear. Prevalence is especially high in unbred and first lactation heifers, causing intramammary infections (IMF) and elevated somatic cell counts. On the other hand, it has been shown that naturally occurring IMI with S. chromogenes, one of the most prevalent CNS, have a considerable protective effect against intramammary challenge with S. aureus (7) and that naturally occurring IMI with CNS in general suppress colonization by other mastitis-causing pathogens (8). By means of in vitro cross-streaking methods, it was shown that 25% of the isolates of the teat normal flora of non-lactating heifers inhibited growth of selected mastitis pathogens. Three out of thirty-five staphylococcus isolates were inhibitory towards gram-positive mastitis pathogens (9). In a more recent study, quarters of heifers of which the teat apex was colonized by S. chromogenes before calving, had significantly lower odds for an elevated somatic cell count during the first five clays of lactation compared with quarters of which the teat apex was not colonized with this bacterium (3). The aim of the present study was toexamine the in vitro inhibitory capability of S. chromogenes originating from teat apices of dairy heifers towards the most important major mastitis pathogens, S. aureus, S. dysgalactiae, S. uberis, and E. coll.