The present invention relates to a novel approach to prevent or treat mastitis both in humans and animals through the use of mammal milk-derived microorganisms obtained from healthy hosts of the homologous species； to those new probiotic microorganisms obtained from milk able to reduce infectious mastitis and the method of screening used for their obtaining； to the use of these probiotic bacteria for the prophylaxis or treatment against mastitis and other diseases； and finally, to compositions comprising these compounds.
