Streamlining of an existing phage amplification assay for viable Mycobacterium avium subsp. paratuberculosis to make it more applicable for large-scale milk testing

Mycobacterium avium subsp. paratuberculosis (MAP) is the causative agent of Johne’s disease in domesticated cattle, sheep and goats, and it may also be involved in the pathogenesis of Crohn’s disease and, potentially, other auto-immune diseases of humans. Infected animals shed the pathogen in their faeces and milk. Studies have shown that pasteurization of milk does not necessarily inactivate the bacterium, so milk and dairy products are considered possible vehicles of transmission of MAP from cattle to humans. There is considerable interest in rapid detection methods for viable MAP that could be used to test milk for diagnostic purposes at farm level or quality control purposes at processing level. Over recent years, QUB researchers have developed and optimized a sensitive and specific test for detecting and enumerating viable MAP by combining peptide-mediated magnetic separation and a phage amplification assay (the PMS-phage assay). However, in its current multi-step format it takes 48 h for a result and the test is neither user-friendly nor suitable for processing large numbers of milk samples. To be suitable for adoption by the dairy industry the PMS-phage assay protocol will need to be simplified whilst maintaining current detection sensitivity.