Persistence and Control of Foodborne Pathogens in Hydroponic Systems

View the project report

Commodities

• Vegetables: greens (leafy), greens (lettuces)

Practices

• Production Systems: hydroponics

Hydroponic farming continues to grow in popularity. Recent outbreaks linked to hydroponic produce highlight the need for improved understanding of how foodborne pathogens persist in these systems and provide a way to control them. The aim of this proposal is to (i) study the persistence of Salmonella, E. coli, and Listeria, in two types of hydroponic systems (deep water culture and Kratky) and to (ii) assess the efficacy of PAA as a pathogen control strategy. In the first objective of this project, pathogens will be inoculated into water to assess their persistence. In the second objective of this project, pathogen control interventions will be assessed to reduce food safety risk while maintaining, or promoting, plant health and productivity. I hypothesize that under conditions where biofilms do not form, the Salmonella and E. coli strains will persist for two weeks, while the Listeria strains will persist for one week as suggested by a previous study (Ilec et al., 2022). I also hypothesize that a treatment of 80ppm PAA for 30 minutes will reduce pathogen load. The findings from this project will help understand the microbial risks and how to manage them in hydroponic farms. Findings will be disseminated among Northeast hydroponic farmers and beyond through the Mid-Atlantic Fruit and Vegetable Convention.

Objective 1: Evaluate the persistence of Salmonella, E. coli and L. monocytogenes in hydroponic systems.

Expected outcome: Characterization of Salmonella, E. coli and Listeria persistence in hydroponic systems in a controlled laboratory setting.

Deliverables: Spreadsheet and graphs with concentrations of Salmonella, E. coli and L. monocytogenes in a nutrient solution over the growing period and the final harvested produce grown in the DWC and Kratky hydroponic systems.

Potential pitfalls and alternative approaches:
We plan to inoculate leafy greens seeds with an inoculum at 10⁸ CFU/ml of Salmonella, E. coli and L. monocytogenes. If this inoculum level leads to concentrations of pathogens that are below the limit of detection of our microbial detection methods, we will collect a larger volume of a sample and filter it in order to obtain quantities of pathogens.

Objective 2: Assess pathogen control steps aimed at reducing pathogens on seeds

Expected outcome: Developed and assessed pathogen control step for seeds that is accessible and feasible for hydroponic farmers to implement to reduce the risk of introducing Salmonella, E. coli and L. monocytogenes contamination in hydroponic systems.

Deliverables: A mitigation step made publicly available to hydroponic farmers in the NE region through a publication and communication at the Mid-Atlantic Fruit and Vegetable Convention.

Potential pitfalls and alternative approaches:
If the mitigation step negatively impacts seed germination, plant growth or plant quality, we will evaluate alternative methods to control bacterial growth. Preliminary small-scale experiments will be conducted to assess these factors.