Common mammary pathogens and factors in infection and mastitis.

Inflammation of the mammary gland, commonly known as mastitis, is considered a complex disease in view of its complexities of etiology, pathogenesis, sequela, therapy, and related aspects. The disease of most concern is the one produced by pathogenic microorganisms. However, as a prerequisite the pathogen must not only enter the mammary gland but also be able to survive and multiply in numbers sufficient to produce pathogenic effects. The normal bovine mammary gland is protected from such attacks by several anatomic and biologic armamenta which must be overcome by the invading pathogens. Organisms involved in causation of mastitis vary in their habitat, virulence, and susceptibility to host barriers. Similarly cows vary in their resistance to microbial entry into the mammary gland and subsequent response to overcome the infection. Only a few organisms, however, need to survive in the milieu of the mammary gland to produce mastitis. This paper is a general discussion of these aspects concerning bovine mastitis in relation to common mammary pathogens.