Establishment of droplet digital PCR for quantitative detection of Listeria monocytogenes in food

ObjectiveA droplet digital polymerase chain reaction （ddPCR） method was developed for the rapid quantitative detection of Listeria monocytogenes in food.MethodsSpecific primers and probes for Listeria monocytogenes were screened. The constant value effect of ddPCR method and plate counting method was compared through the detection of pure bacterial solution and artificially contaminated samples. The specificity， sensitivity and repeatability of ddPCR method were analyzed.ResultsThe ddPCR had the characteristics of excellent specificity， sensitivity and repeatability in Listeria monocytogenes detection. The limit of detection （LOD） and the limit of quantification （LOQ） in pure bacterial solution were 136 CFU/mL. The LOQ in squid ring and sausage samples was 240 CFU/g and 155 CFU/g. The coefficient of variation of ddPCR was less than 25% at each gradient level， and the relative deviation of the logarithm of ddPCR and plate counting was less than 30%.ConclusionThe established ddPCR method is rapid， accurate， sensitive and specific for the quantitative detection of Listeria monocytogenes in food.