Detection of viable Mycobacterium avium subsp. paratuberculosis using luciferase reporter systems

Plasmid- and phage-based firefly luciferase reporter constructs were evaluated as rapid detection systems for viable Mycobacterium avium subsp. paratuberculosis (MAP). A MAP strain bearing a luciferase-encoding plasmid was detectable at 100 cells/mL in skim milk and 1000 cells/mL in whole milk. Three luciferase-encoding mycobacteriophage were evaluated for detection of wild-type MAP. The best of these, phAE85, allowed detection of >1000 cells/mL within 24-48 h. Membrane filtration did not improve the sensitivity of detection for either plasmid or phage reporters. Luciferase reporters show promise for rapid detection of viable MAP.