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

Authors: RAO, AISHWARYA - University Of Maryland; PRADHAN, ABANI - University Of Maryland; Patel, Jitendra

Submitted to: Journal of Agriculture and Food Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/22/2025
Publication Date: 2/23/2025
Citation: Rao, A.P., Pradhan, A.K., Patel, J.R. 2025. Transfer of Salmonella enterica, Escherichia coli O157:H7 and Listeria monocytogenes to microgreens and soil from contaminated seeds. Journal of Agriculture and Food Research. 21. Article e101761. https://doi.org/10.1016/j.jafr.2025.101761.
DOI: https://doi.org/10.1016/j.jafr.2025.101761

Interpretive Summary: Microgreens are prone to contamination because of the environmental conditions they are grown in. Further, there is no post-harvest treatment to minimize contamination on microgreens. We evaluated potential transfer and persistence of bacterial pathogens from contaminated seeds to four microgreens (broccoli, mustard, red cabbage, daikon). All three pathogens, Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes, were transferred from contaminated seeds to microgreens harvested at 7 and 14 days. The persistence of these pathogens decreased on day 14 compared to their populations on day 7. Pathogens were also found in soil used for growing microgreens. In general, lower persistence of Salmonella and Listeria monocytogenes was found in red cabbage and mustard, respectively. Growers can use the results in seed decontamination to minimize potential transfer of pathogens from seeds to microgreens.

Technical Abstract: 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 trend of Salmonella enterica, Escherichia coli O157:H7 and Listeria monocytogenes was 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.