**4.3 Multiplex polymerase chain reaction (PCR)**

Multiplex PCR is a variant of the PCR technique in which two or more loci are simultaneously amplified in the same reaction. Multiplex PCR can be described as a specific and sensitive in vitro amplification of DNA with distinguishable size products from the same or different organisms in a single reaction (Jasson et al., 2010; Fitzgerald et al., 2007). In this methodology several specific primer sets are combined into a single PCR assay. MPCR is undoubtedly useful to rapidly establish simultaneous detection of multiple virulence factors (Fach et al., 2009) or combined detection of multiple isolates (Kawasaki et al., 2009; Settanni & Corsetti, 2007). A convened format for MPCR is the GeneDisc (PALL) (Beutin et al., 2009).

Recently, multiplex real-time PCR assays have been applied to detect more than two gene sequences in a single reaction by using spectrally distinct dye-labeled probes (TaqMan system) (Elizaquivel et al., 2008). This technology could potentially save time and effort in the laboratory and thus may lower testing-related costs incurred by the food industry (Elizaquivel et al., 2008).
