Rapid and Sensitive Detection of L. monocytogenes with Loop-mediated Isothermal Amplification (LAMP) Method Targeting prfA Gene

Introduction: Listeria monocytogenes is one of the major foodborne pathogens that causes human listeriosis. Developing a rapid and sensitive screening method is important for the detection of the target pathogen present in various food matrices from a public health perspective.

Purpose: The aim of this study was to develop a rapid and sensitive detection tool for screening L. monocytogenes by using Loop-mediated isothermal amplification (LAMP) assay targeting prfA gene.

Methods: The LAMP assay in pure culture suspension (in 0.85 % NaCl solution) was performed at 62.5°C for 30 min to determine the inclusivity, exclusivity and the LoD of the assay. The LoDs of the LAMP assay in Listeria enrichment broth for 24 h incubation (LEB24) and LEB artificially contaminated with milk for 24 h incubation (LEB24-M) were determined and compared with those of PCR and real-time PCR assays.

Results: The inclusivity and exclusivity were 100 % and the limit of detection (LoD) was 2.22×10² CFU/ml at 19.5 min in pure culture suspension. The LoD of the LAMP assay in LEB24 was 2.22×10⁰ CFU/ml which is identical with the real-time PCR result but 10² times sensitive than the PCR result. The LoD of the LAMP assay in LEB24-M was 2.22×10⁰ CFU/ml which is 10 and 10² times sensitive than real-time PCR and PCR results, respectively.

Significance: These data indicate that the LAMP assay is a rapid, simple and sensitive assay which could be used as a potential screening tool of L. monocytogenes.