الكاتب: Multiple References

Research from our laboratory has shown that several bovine mastitis pathogens adhere to and internalize into bovine mammary epithelial cells (Matthews et al., 1994; Almeida & Oliver, 1995; Almeida et al., 1996a,b). We hypothesize that adherence and internalization are important virulence attributes of bovine mastitis pathogens. Adherence is important for bovine mastitis pathogens once they gain entry into the udder. Otherwise bacteria would be removed quite easily by fluid flow during milking. Internalization of bovine mastitis pathogens into the cytoplasm of mammary epithelial cells allows pathogens an opportunity to reach the intracellular microenvironment. There is indirect evidence of internalization into bovine tissue. Oliver et al. (1998) demonstrated that the same clonal type of Streptococcus uberis was isolated from the same mammary quarter for more than one lactation period. Once internalized, mastitis pathogens could infect deeper regions of the affected bovine mammary gland resulting in the development of chronic intramammary infections. Following internalization, components of the immune system such as polymorphonuclear neutrophils, macrophages and antibodies; nonspecific antibacterial factors present in bovine milk; and antibiotics that do not cross mammary epithelial cell membranes are essentially ineffective. Therefore, it would appear that central to the control of several bovine mastitis pathogens is the ability of antibiotic preparations used in the treatment of mastitis to penetrate into host cells and kill intracellular bacteria within the cytoplasm of mammary epithelial cells.