Transfer of Salmonella enterica, Escherichia coli O157:H7 and Listeria monocytogenes to microgreens and soil from contaminated seeds

In recent years, the consumption of novel salad greens such as microgreens has increased tremendously around the globe because of their health and nutritional benefits. These benefits that include antioxidant activity among others have been attributed to the presence of helpful bioactive compounds. However, due to their production methods and conditions, they have a risk profile that bears a few similarities to that of sprouts. The persistence trends of Salmonella enterica, Escherichia coli O157:H7 and Listeria monocytogenes were studied over the growth period of 14 days. Seeds of daikon, mustard, broccoli, and red cabbage microgreens were contaminated with the three pathogens at high (∼5 Log CFU/g) and low (∼3 Log CFU/g) levels and the microgreens and soil were sampled on days 7 and 14. Microbiological analysis of soil and microgreen samples was carried out using spiral-plating on pathogen specific selective agars. There was a distinct increase on day 7 in the populations of all three pathogens in both the edible leafy green shoot portions and the soil of the microgreens. However, the prevalence levels of all three pathogens decreased by day 14. On day 7, there was no significant difference in the persistence of E. coli and Salmonella in all four microgreens. However, the L. monocytogenes populations were significantly higher in red cabbage than in broccoli, mustard and daikon. On day 14, the levels of all three pathogens did not significantly vary in the microgreens or the soil in which the microgreens were cultivated. In general, lower persistence of Salmonella and .L. monocytogenes was found in red cabbage and mustard microgreens on day 14, respectively. Results suggest that foodborne pathogens can be transferred from contaminated seeds to microgreens and persist in edible portions of microgreens at the point of harvest. Stringent quality assurance measures are required in maintaining microbial quality of seeds to prevent contamination and potential food safety risks.