Enumeration of viable Listeria monocytogenes cells by real-time PCR with propidium monoazide and ethidium monoazide in the presence of dead cells.

ABSTRACT

Propidium monoazide (PMA) and ethidium monoazide were used for enumeration of viable Listeria monocytogenes cells in the presence of dead cells. PMA had no antimicrobial effect on L. monocytogenes. Viable cell counts were linearly related to real-time PCR threshold cycle values for PMA-treated cells from planktonic and biofilm sources over a 4-log range.