Foodborne pathogens in horticultural production systems: Ecology and mitigation

Foodborne pathogen outbreaks have become an increasing problem in the horticultural industry due to changes in diets, production, processing and distribution practices, as well as greater awareness and detection. Once produce is infected, outbreaks can spread rapidly resulting in illness and even death among large groups of people. Strict new food safety laws have been implemented to reduce risks, but outbreaks are still occurring. Pathogens with the greatest threat in ready-to-eat horticultural crops include Salmonella enterica, Escherichia coli (STEC), and Listeria monocytogenes, with contamination introduced through animal manure, water, seeds and plant debris. While previously thought to be only transient inhabitants of horticultural production systems, it is now clear that enteric pathogens are adapted to survive for prolonged periods outside of their animal hosts, attaching tenaciously to plants via biofilm formation and internalization in plant tissues. Management practices including treating animal manure, water and seeds, increasing soil biological diversity and activity, and limiting damage to plants via pests and equipment can help reduce food safety risks in pre-harvest production systems. Further reducing food safety risks in these systems will require innovative, interdisciplinary research that integrate the fields of soil microbial ecology, plant pathology, plant breeding and engineering. Specifically, we advocate for additional research to: 1) better understand how soil and phyllosphere ecology affects pathogen residence time, 2) identify key traits and markers to integrate selection for enteric pathogens into crop breeding programs, and 3) develop new detection technologies that rapidly and accurately detect enteric pathogens on produce.