EXPERIMENTAL STAPHYLOCOCCAL MASTITIS I N T H E MOUSE: EFFECTS O F EXTRACELLULAR PRODUCTS AND WHOLE BACTERIAL CELLS FROM A HIGH-VIRU-

THE technique of inoculation of staphylococci into the mammary gland of the mouse (Chandler, 1970) has been used to demonstrate that strains of Staphy Zococcus aureus differ in their virulence as assessed by the clinical response, the number of bacteria recovered from the infected glands and the histopathological lesions induced (Anderson, 197 1, 1972). The inoculation of cell-free staphylococcal " toxin " i.e., total extracellular products into the mammary gland of the mouse causes death, and the inoculation of diluted " toxin " produces a coagulative necrosis consistent with the action of a-toxin (Anderson and Mason, 1974). In the present study a comparison was made of the effect of cell-free toxic preparations and live staphylococci derived from two strains. One strain was known to be of high virulence and the other of low virulence in the mammary gland of mice and cattle (Anderson, 1971; Reiter et al., 1971). MATERIALS AND METHODS Mice. Lactating mice of the BSVS strain were used between the 3rd and 6th day afte