The mouse mastitis model: Observations relevant to the treatment and control of coliform mastitis

The response to intramammary inoculation ofEscherichia coli in mice is described and the contribution of endotoxin to the clinical signs is considered. The implications of these responses for therapy are examined. The role of the neutrophil is assessed and it is considered that the rate of arrival of neutrophils in the gland is of more importance in limiting infection than the number of existing neutrophils at the time of challenge. The effect of inducing a neutrophil response by colonization of the gland by a pathogen of low virulence is described and the dangers of inducing chronic infections are emphasised. Using a modification of the mouse model in which organisms are placed on the tip of damaged or undamaged teats of suckling or non-suckling mice it is demonstrated by the pattern of response that staphylococci actively colonize the teat and subsequently invade the gland whereasE. coli infections result from the chance entrance of contaminating organisms.