Bacterial attenuation method and vaccine

Abstract From the Canadian patent

Disclosed herein are methods for attenuating virulent Gram negative bacteria to produce avirulent bacteria. The methods comprise passaging the wild-type bacteria through phagocytic cells such as macrophages or polymorphonuclear leukocytes or, through lysosomes derived from such cells a sufficient number of times until the bacteria become avirulent to the animal host. The bacteria are preferably from the family Enterobacteracea and most preferably from the genus Salmonellae. The invention further comprises the avirulent bacteria produced by the methods pure cultures of such bacteria, and methods of using the bacteria, preferably in a vaccine for administering to an animal host to induce an …