California / Australian Black Worms i.e. Lumbriculus variegatus and Mycobacterium PCR

I have read the various opinions on whether black worms, Lumbriculus variegatus, can or can't serve as a vector for mycobacteria.
Mycobacteria are well known to be transmitted through many members of the food web including protozoa, tubifex, daphnia and mosquito larvae. I hear the arguments that tubifex live in 'dirty' water and black worms like 'clean' water and therefore black worms are safe / mycobacteria free.
Science has progressed in leaps and bounds in the last decade. With the new PCR techniques, has anyone ever tested Lumbriculus variegatus with the supersensitive Mycobacterium PCR?
If I put it another way, has any grower/supplier ever proven their product to be Mycobacterium PCR negative?