An attenuated strain used for vaccines. Brucella abortus S19

Brucella abortus S19. This is a spontaneously attenuated strain discovered by Dr. John Buck in 1923. However, the underlying molecular or physiological mechanisms causing the loss of virulence is not well understood. Since early 1930s, this strain has been used worldwide as an effective vaccine to prevent brucellosis in cattle until it was replaced by strain RB51 during the 1990s. The main objective of this project is to identify genes associated with the virulence or lack there of, through comparison of S19 genome with that of the virulent counterparts.