Real-time PCR identification of Listeria monocytogenes serotype 4c using primers for novel target genes obtained by comparative genomic analysis

Abstract Detection of the foodborne pathogen Listeria monocytogenes serotype 4c, one of the predominant serotypes in aquatic products, is difficult and time-consuming. Our objective was to identify novel target genes for real-time PCR detection of L. monocytogenes serotype 4c using comparative genomics to facilitate its specific identification in food products. A total of 160 Listeria genome sequences, including those of 12 L. monocytogenes serotypes and 14 other Listeria species, were employed to identify serotype 4c-specific targets. Two serotype 4c-specific genes (SLCC2376_00062 and SLCC2376_00822) were obtained. Using primers for SLCC2376_00822, a real-time PCR assay for the detection of serotype 4c was developed. The specificty of this assay was robustly verified by other serotypes of L. monocytogenes and non-L. monocytogenes strains. In addition, this real-time PCR method could accurately detect serotype 4c even when mixed with different concentrations of serotypes 1/2a and 1/2b. Furthermore, the assay could successfully detect 1.4 × 109–1.4 × 103 CFU/g of L. monocytogenes serotype 4c in artificially contaminated grass carp without enrichment. These results demonstrate that the assay, which has high accuracy and sensitivity, comprises a promising approach for the detection and identification of L. monocytogenes serotype 4c strains in foods.