Novel Strategies for Determining Thermal Destruction of Mycobacterium paratuberculosis

The American dairy industry annually loses $120 million to Iohne's disease, an incurable bacterial infection in cattle. The infection is caused by the bacterium Mycobacterium paratuberculosis. Infected cattle shed M paratuberculosis into milk and feces, posing a possible health risk to humans. Although pasteurization of raw milk kills most spoilage and pathogenic microorganisms, isolation of M paratuberculosis from humans suffering from Crohn's disease, an incurable inflammatory bowel disease with clinical symptoms similar to Iohne's disease, suggests a possible causal relationship. Processing times and temperatures that will enhance destruction of M. paratuberculosis in milk remain to be established. Current standard culturing techniques for enumerating viable M paratuberculosis cells will detect the presence of low numbers, but are laborious, time-consuming and may not allow detection of sublethally heat injured, viable butnon-culturable cells (VNC). The VNC may represent a significant proportion of cells surviving heat treatment. To better establish whether M paratuberculosis cells are killed by pasteurization, we will use M. paratuberculosis strains engineered to produce light when viable to test the efficacy of pasteurization and to develop a strategy for screening for the presence of M paratuberculosis in raw and processed milk. At the conclusion of this project, we will have established specific heat treatment parameters for the destruction of M paratuberculosis and will have developed a rapid detection method to improve dairy herd health management.