Interaction between Food-borne Pathogens (Campylobacter jejuni, Salmonella Typhimurium and Listeria monocytogenes) and a Common Soil Flagellate (Cercomonas sp.)

Free-living protozoa may harbor, protect, and disperse bacteria, including those ingested and passed in viable form in feces. The flagellates are very important predators on bacteria in soil, but their role in the survival of food-borne pathogens associated with fruits and vegetables is not well understood. In this study, we investigated the interactions between a common soil flagellate, Cercomonas sp., and three different bacterial pathogens (Campylobacter jejuni, Salmonella Typhimurium, and Listeria monocytogenes). Rapid growth of flagellates was observed in co-culture with C. jejuni and S. Typhimurium over the time course of 15 days. In contrast, the number of Cercomonas sp. cells decreased when grown with or without L. monocytogenes for 9 days of co-culture. Interestingly, we observed that C. jejuni and S. Typhimurium survived better when co-cultured with flagellates than when cultured alone. The results of this study suggest that Cercomonas sp. and perhaps other soil flagellates may play a role for the survival of food-borne pathogens on plant surfaces and in soil.