CPS – Research project Funding 2022 – Salads


Assessing Romaine lettuce “Forward Processing” for potential impacts on EHEC growth, antimicrobial susceptibility, and infectivity

Consumption of Romaine lettuce has been linked to multiple foodborne illness outbreaks due to contamination of pathogenic Escherichia coli strains. Recently, these outbreaks have occurred in the United States every year since 2016, causing great damage to consumer health and economic wellbeing of the fresh produce industry. The pathogen strains isolated from these outbreaks showed great similarity by genomic analyses. These outbreaks showed a pattern of heavy concentration especially in northeastern USA, prompting questions from the leafy green industry that the practice of “forward processing” could be linked to the outbreaks. “Forward processing” is a practice that the raw lettuce commodity is transported in trucks to facilities far away from the production area for washing and packaging, and regional marketing. We propose to work closely with the leafy green industry to comprehensively assess the forward processing for its effects on the integrity and safety of the raw commodity and the packaged products. In addition, the forward processing conditions will be simulated in the laboratory with the pathogenic E. coli strains. Emphases will be on how these conditions would affect the physiology of the pathogenic strains as well as other microorganisms on the raw commodity and packaged products. The findings in the research could provide important information that can be used by the leafy green industry for improving the forward processing practice and reducing the risks of fresh produce such as Romaine lettuce.


Quantifying risk associated with changes in EHEC physiology during post-harvest pre-processing stages of leafy green production

The goal of this project is to determine if the time between harvest and end use of romaine lettuce impacts E. coli O157:H7 pathogenicity and detectability resulting in increased health risk. Laboratory scale experiments with inoculated lettuce undergoing simulated harvest and cooling will be used to measure changes in E. coli O157:H7 stress tolerance and virulence. Input from industry partners including temperature data from commercial romaine harvesting and cooling, and details on supply chain logistics, will be combined with the laboratory scale experimental data and used to model risk associated with specific harvest and handling practices. The resulting quantitative tool will be publicly available and allow for growers and producers to determine any practices that should be implemented to reduce the potential for O157 transmission on romaine lettuce.

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