Simultaneous detection of pathogenic Listeria including atypical Listeria innocua in vegetables by a quadruplex PCR method

Listeria species are major foodborne pathogens that are the causative agents of listeriosis, a severe infection with high fatality rates. The development of rapid methods to detect the potential presence of pathogenic Listeria is important, particularly in the food industry. In this study, we developed a quadruplex PCR method for simultaneous detection and differentiation of Listeria monocytogenes, Listeria ivanovii, Listeria innocua, and atypical L. innocua. The specificity of this PCR method was tested with 28 strains, including 15 Listeria strains and 13 other bacterial strains. The developed PCR method could detect target sequences in 0.1 ng/μL of genomic DNA present in the reaction mixtures. By employing a combination of four primer pairs, all targeted Listeria species were successfully differentiated within a single reaction. Up to 1–10 CFU in 20 g green romaine vegetable samples could be detected after 24 h enrichment. The quadruplex PCR method developed in this study may be a useful alternative to culture-based methods for the routine detection of Listeria in the food industry. •A quadruplex PCR method was developed to simultaneously detect pathogenic Listeria.•L. monocytogenes, L. ivanovii, and typical and atypical L. innocua were targeted.•There were no cross-reactions of PCR between Listeria species or other bacteria.•The quadruplex PCR method could detect up to 0.1 ng/μL of DNA.•The assay could detect 1–10 CFU in 20 g vegetable samples after 24 h enrichment.