Detection of multiple virulence-associated genes of Listeria monocytogenes by PCR in artificially contaminated milk samples.

The inhibitory effect of milk in the PCR detection of Listeria monocytogenes could be overcome by washing the contaminated milk sample with phosphate-buffered saline and concentrating the bacteria to 1/10 of the original volume. In order to avoid a possible failure in the detection of virulent L. monocytogenes, a one-step procedure which enabled demonstration of three virulence-associated genes, prfA, hlyA, and plcB, simultaneously in a single PCR mixture was developed.