Research recently released by the Fresh Express Company has added greatly to our knowledge of the route of transmission of E coli O157:H7 in leafy greens. A research team including Michael T. Osterholm, PhD, MPH at the University of Minnesota and Dr Michael Doyle of the University of Georgia found that flies can carry E coli to the stomata of the plant (the opening in the plant where gases are exchanged). Once there the E coli find a rich environment and can colonize the site through newly discovered virulence mechanisms. The study also found that the E coli were unable to actually infect the inner vascular structure of leafy greens through roots or leaves.
The research points to a key pathway for disease transmission that needs to be broken. While some filth flies are inevitable in farming operations there are some common sense things that must be considered in reducing fly populations, and those are the presence of decaying matter and fecal material on the farm and proximately to large cattle operations and manure.
The comments of Mr. Jim Prevor the highly respected Perishable Pundit provide an important industry perspective. While Mr. Prevor praises the results of the research, he also points out that applying what is developed in a scientific model to the real world requires something more. Mr Prevor writes "Although this type of quick turnaround can provide important clues for further research and provide the trade and regulators with some notion of how research is progressing, we think demanding instantaneous revolutions in horticultural and processing practices is too much." Mr.Prevor then goes on to praise the research, adding, "For today, however, the industry owes a big hat tip to Fresh Express. We know more and have a clearer path to food safety than we did last week. That is a formidable accomplishment".
I can understand Mr. Prevor’s dilemma, there are obvious implications for agricultural now that we know the dangers of filth, flies and the vulnerability of the stomata. On the other hand, there are simple and practical things that we might attempt. Some questions to explore:
Just how does one control filth and flies in farming operations?
What do we do with knowledge about E coli’s colonization of the stomata?
Is ozone or some other treatment the answer, are there alternatives?
If more research is needed, what kinds of things should we be looking at?
The produce industry needs to be looking for answers to these questions. Can the industry afford to write off 2 million dollars of their own research money? The produce industry cannot excuse itself citing potential costs or difficulties. Stay tuned as I explore these questions and implications for consumers, industry, regulatory agencies and food safety professionals.
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