Although there were some discordant results observed between multiplex PCR and traditional cultures. the results were highly consistent with the exception of two samples. Beef sample number four gave a positive result for L. monocytogenes by the traditional culture method but was negative in the PCR method. This can be explained that analysis of the result may be that other Listeria species like L. innocua, which is a nonpathogen and lacks the hlyA gene, can also grow on the PALCAM agar as L. monocytogenes.
In the other hands, chicken sample number two gave a positive result for Sh. flexneri by the PCR method, but a negative result by the culture method. It probably caused by A 230-kb virulence-associated invasion plasmid, required for entry into host cells, involving a cluster of genes, appears in Shigella and enteroinvasive E. coli (EIEC) strains