Jeff LeJeune, a microbiologist with Ohio State University’s Ohio Agricultural Research and Development Center, is leading a new research project aimed at determining the processes that impact growth and survival of E. coli O157 (the strain involved in the spinach outbreak) on and in vegetables.

LeJeune hope that he will be able to develop practical knowledge that could lead to new ways to reduce bacterial contamination in the produce that people are so encouraged to eat every day. The project includes an outreach component aimed at delivering educational programs that vegetable growers need to improve food safety.

Other collaborators in the project — funded at more than $600,000 by the U.S. Department of Agriculture’s Cooperative State Research, Education, and Extension Service — are the College of Wooster and Michigan State University.

Regardless of the source of contamination in the field, LeJeune explained, E. coli finds a way to survive and reproduce on the surface of vegetables — and even worse, inside the plant tissue, where it cannot be washed off or killed by disinfectants. LeJeune and colleagues propose that the interaction between E. coli O157 and plant pathogens results in increased E. coli uptake, proliferation, exchange of antibiotic resistance genes, and protection from post-harvest disinfection.

In other words, if vegetables are under siege by plant diseases and become tainted with E. coli, the nasty foodborne bacteria will have a better chance of surviving and multiplying in our next fresh salad — and it will be harder, if not impossible, to get rid of it.

Specifically, LeJeune and colleagues are trying to prove the following hypotheses:

  • In the presence of plant-pathogenic bacteria that secrete plant tissue-degrading enzymes, E. coli O157 will proliferate to greater numbers and is more likely to be systematically disseminated to edible plant tissues than in the absence of plant pathogens.
  • Pre-harvest contamination of edible plant surfaces with bacterial foodborne pathogens reduces the chance of success of post-harvest disinfection procedures, as E. coli O157 becomes protected in the plant tissue.
  • Plant pathogens serve as a reservoir of antibiotic resistance genes present in human pathogens, and these genes are transferred from plant pathogens to E. coli O157 in plant lesions.
  • Seeds produced by plants contaminated with foodborne pathogens will be contaminated internally with bacterial pathogens and produce contaminated products.