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.
U.S. Department of Agriculture, Agricultural Research Service, and North Carolina Agricultural Research Service, Department of Microbiology, North Carolina State University, Raleigh, NC 27695-7624, USA.
