Foodborne illness strain of E. coli found in hydroponic and aquaponic food production, indicating need for food safety monitoring

Hydroponic food production can help address challenges in terrestrial farming like shortages of water and good quality land.  Food safety concerns have been raised, particularly when fish are incorporated into the system (aquaponics), because water is recycled to grow produce that is aimed to be eaten fresh and uncooked. A recent study published in the journal Horticulturae discovered the strain of E. coli that causes foodborne illness can be found in aquaponic and hydroponic systems, indicating that food safety in these systems must be carefully monitored and controlled. Rather than growing food in soil, hydroponic food production uses a closed-loop system that recycles water and nutrients. Aquaponics adds fish to the loop to naturally produce nutrients for the crops. This study measured the occurrence of three foodborne pathogens: the shiga toxin-producing strain of E. coli (STEC), Listeria monocytogenes, and Salmonella spp. in greenhouse-based aquaponic and hydroponic production of lettuce, basil and tomato crops. The researchers screened fish feces, water, roots and all edible portions of the crops for these pathogens. No Listeria nor Salmonella were found in any part of the production system or plant tissues. However, they did find STEC contamination in fish feces, water of both aquaponic and hydroponic systems, and the surface of root tissue from all three crops. They did not find STEC had moved into any edible tissues of the plant. While hydroponics can be a sustainable method to produce food in limited resource situation, the results from this study suggest that foodborne pathogens can exist and be recycled in this closed-loop system. Close monitoring and care in food-handling can help mitigate this risk.  The current position from the National Organic Program (NOP) is that organic certification of hydroponic production systems is allowed as long as the producer can demonstrate compliance with the organic regulations.