Integrating sustainability & food safety: assessing Salmonella serovar fitness in irrigation water & transfer onto crops

View the project final report

Commodities

• Vegetables: tomatoes

Practices

• Crop Production: irrigation, water management
• Education and Training: decision support system, extension, workshop

Surface water is a viable and renewable source of irrigation for agricultural crops in the Northeastern United States. However, surface water is a known reservoir of the foodborne pathogen Salmonella enterica. Recent regulation requires farmers to monitor irrigation water quality based on Escherichia coli levels. Failure to meet the set microbial standards necessitates mitigation measures or employment of other sources of water that meet the standards. Treatment options are limited or partially effective and could incur a disproportionate financial cost on smaller farms. Alternatively, resorting to groundwater as an irrigation water source would place a burden on an important natural resource in the long-term. In spite of recommendations not to use water with high E. coli levels, E. coli is a poor predictor of Salmonella presence. Furthermore, Salmonella ecology and growth dynamics in surface water and transfer potential onto crops are not well understood. More in-depth evaluation of the “true” risk of Salmonella in irrigation water is needed. The purpose of this study is to evaluate the observed Salmonella risk during irrigation of fresh produce crops by assessing viability of S. enterica in surface waters, transferability from water to crops, and adaptation to water environments. We will collaborate with the Maryland Department of Agriculture (MDA) to disseminate data at Food Safety trainings for growers. Results from this study will augment current knowledge of Salmonella risk in irrigation water and inform ongoing efforts to develop equitable and sustainable practices for irrigation, minimizing unnecessary depletion of groundwater resources and enhancing food safety.

The goal of this project is to evaluate the observed Salmonella risk to fresh produce safety in multiple surface water types.  Specifically, I propose to assess Salmonella serovar viability in surface water over time, and investigate the degree of Salmonella transferability from surface water to fresh produce crops in growth chamber trials.  Additionally, I plan to evaluate whether Salmonella adaptation to water environments increase the risk of water-crop transfer. Finally, in collaboration with the MDA I plan to enhance grower education by incorporating a seminar on irrigation water in Food Safety Trainings, sharing research findings and discussing the importance of balancing food safety practices with environmental stewardship.  The goal of this project is to evaluate the observed Salmonella risk to fresh produce safety in multiple surface water types.  Specifically, I propose to assess Salmonella serovar viability in surface water over time, and investigate the degree of Salmonella transferability from surface water to fresh produce crops in growth chamber trials.  Additionally, I plan to evaluate whether Salmonella adaptation to water environments increase the risk of water-crop transfer. Finally, in collaboration with the MDA I plan to enhance grower education by incorporating a seminar on irrigation water in Food Safety Trainings, sharing research findings and discussing the importance of balancing food safety practices with environmental stewardship.  

The objectives of this study are:
1) SURVIVAL: Measure the growth dynamics of multiple serovars of Salmonella in various types of surface irrigation water sources in Maryland.  Fate of multiple Salmonella serovars in water samples representative of pond, non-tidal, and tidal river waters will determine whether viability in water is significantly influenced by water type or serovar. Salmonella will be quantified by both dilution plating and quantitative-PCR (q-PCR) using a standard curve that will enumerate not only culturable, but also non-culturable persistor phenotypes. Assessment of biofilm formation in these water microcosms will determine Salmonella serovar-dependent risk of biofilm formation in water distribution systems used in irrigation. 

2) TRANSFERABILITY and ADAPTABILITY: Determine transferability potential of two Salmonella serovars from water to crops, and assess pre-adaptation to the plant-niche.  I will assess the ability of Salmonella to establish on tomato via irrigation water contaminated with varying concentrations of this pathogen. This will investigate the relationship between Salmonella hazard in water and observed risk on plants.  Biofilm formation, surface attachment, and stress response genes may be important for successful transfer of Salmonella onto plants. Gene expression analysis of these will evaluate Salmonella pre-adaptation to plant surface colonization.    

3) FOOD SAFETY EDUCATION to MARYLAND GROWERS:  Enhance food safety education for growers on water quality, testing requirements, and new research findings.  Specifically, I will design a factsheet for online dissemination, and give seminars as part of Food Safety Trainings conducted by the MDA in collaboration with UMD. I will teach growers functional knowledge about water quality and testing, and employ scenario based case studies targeting best practices for addressing on-farm food safety risk factors. These seminars will also provide a platform to highlight the importance of implementing food safety measures while considering environmental sustainability and conservation.