Rapid and visual detection of Listeria monocytogenes by combining one-pot LAMP-CRISPR/Cas12b with lateral flow assay

Listeria monocytogenes, the leading cause of fatalities worldwide among foodborne pathogens, poses serious risks to food safety and public health. Therefore, a rapid and accurate detection method is crucial for early interception and effective management. In this study, a one-pot LAMP-CRISPR/Cas12b detection system based on the lmo0753 gene was developed for rapid detection of L. monocytogenes by combining loop-mediated isothermal amplification (LAMP) with a CRISPR/Cas12b assay. Further integration of a lateral flow assay (LFA) to develop a LAMP-CRISPR/Cas12b-LFA assay enabled direct detection of the results on the strips with the naked eye. Nine L. monocytogenes strains belonging to eight serotypes tested positive with both the one-pot LAMP-CRISPR/Cas12b and LAMP-CRISPR/Cas12b-LFA assays. Two assays did not show cross-reactivity with L. innocua and eight other foodborne bacteria. The limits of detection were 10 CFU/mL for pure culture and 20 CFU/g for spiked pork samples. Moreover, the enrichment time was substantially shortened to 3 h for pork samples spiked with only L. monocytogenes F2365, and 4-5 h for pork samples spiked with mixed bacteria. In addition, with one-pot LAMP-CRISPR/Cas12b detection, 5 of 66 fresh pork samples, 1 of 20 ready-to-eat food samples, and 2 of 24 raw milk samples tested positive for L. monocytogenes, in agreement with the results obtained through a culture based standard method. Thus, this study established one-pot LAMP-CRISPR/Cas12b and LAMP-CRISPR/Cas12b-LFA assays for rapid, visual detection of L. monocytogenes in food samples.