LAMP based electrochemical sensor for extraction-free detection of Listeria monocytogenes in food samples

Listeria monocytogenes (LMO) represents one of the most serious hazards for food health due to the high mortality rate and its ability to survive at limiting conditions. In this study, an electrochemical sensor for the detection of LMO in food samples using loop mediated isothermal amplification (LAMP) technique is presented. The extraction step for the release of the nucleic acids of the sample was simplified using three different alternatives (QuickExtract buffer lysis, heating method and an extraction-free option). The three protocols were tested with the LAMP reaction in seven different food matrices (Dairy milk, fresh cheese, ham, hummus, lettuce, milk powder and pâté) and were able to detect 1 cfu / 25g as stipulated by the food safety regulations. It was proved that all three alternatives were compatible with the electrochemical detection using methylene blue redox-active molecule in dairy milk samples. The final validation of the sensor was carried out with the extraction-free option in nine different food matrices, which were able to detect 1 cfu/ 25g of food sample in all cases. This validation demonstrates the feasibility of the sensor for its application in the food industry as a point-of-test solution.