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A Review of the 2016 Center for Produce Safety Research Symposium

Last week the Center for Produce Safety (CPS) held its annual Research Symposium in Seattle. The symposium was well received and attended, with approximately 350 registrants from all over the world. The leafy greens industry was well represented, with twenty LGMA handler-members in attendance.

Although there were many interesting research reports presented during this event, two that stood out were: an in‐depth case study on the Listeria monocytogenes (Lm) outbreak involving caramel apples, and a series of “Lightning Rounds” and “Poster Briefs” with summaries and discussion of select research projects.

This two‐part case study on Listeria was one of the highlights of the symposium. The first part of the session covered the scope and scale of the outbreak from regulatory and industry perspectives, while the second part covered what was learned from the subsequent investigation.

The information presented was interesting from many perspectives. First, and most tragically, the outbreak had a very high mortality rate. The presentation from the regulatory officials at both the U.S. Centers for Disease Control and the California Department of Public Health into tracing the cause was fascinating. Once the outbreak was traced to a central California apple packing house, it was found that Listeria was still present, even months later when the environment in the packing was dry and completely free of water. This upended some of the conventional thinking about Listeria and its ability to survive in dry environments.

Like the spinach outbreak in 2006, the entire apple industry was affected by this outbreak. Shippers from Washington State not only felt the impact on their domestic sales, but also saw international shipments briefly interrupted as governments around the world reacted to news of the outbreak.

Finally, it was interesting to hear how whole genome sequencing has become a valuable tool for state and federal officials as they investigate outbreaks. This was a recurrent theme throughout the Symposium and is something we can expect to hear a lot more about as we move forward.

Sessions and Posters:

Many of the research studies that were presented as part of Lightning Rounds (brief presentations about ongoing or new research presented by the researchers themselves) are relevant to the leafy greens industry. Some of the key topics of interest included:

  1. Surrogates and Indicators: During this round attendees learned, among other things, that Bacteriodeles may prove to be better indicators for the presence of fecal contamination in water tests and that phages may be important as a capture device. In summary, there is a need to better understand the physical and chemical parameters of the organisms being used as surrogates.
  2. Irrigation Water Management: This round featured presentations indicating just how dynamic canal systems can be, with several researchers raising questions about the correlation between generic E. coli and presence of pathogens in water. One study showed that there appears to be little difference in test results when samples are taken from several points in the canal. This is significant from a practical standpoint and may make future canal water sampling easier since many of our current protocols call for sampling in certain parts of the canal only.
  3. Animal Intrusion and On‐Farm Pathogen Detection: Some interesting work is being done in the area of environmental assessments. One report indicates that birds and rodents are the most common animals entering fields, while another indicates that survival and persistence of Norovirus is not particularly applicable to growing conditions in California and Arizona.
  4. Flooding: One of the posters presentations attendees saw involved flooding. One of the key findings of this project is that working the ground too soon after a flooding event may in fact promote pathogen growth. Another indicated that solarization of soil for 36 days is effective in eliminating Salmonella.

As is always the case, these studies will require further research and validation. We applaud CPS and all of its partnering researchers and institutions for their work, and we thank the many companies – including several LGMA members – who have donated generously to keep the CPS effort funded.


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