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Marler Blog Providing Commentary on Food Poisoning Outbreaks & Litigation

E. coli Outbreaks still a Risk in Leafy Greens

I spent the day is a well-run, informative, conference sponsored by Fresh Express (never sued them). The science was interesting and well presented. The bottom line however is there is far more research needed and the risks to consumers are still quite real in the consumption of “ready-to-eat” products. Here are some of the highlights from the scientists:

1. Contamination can spread during washing, cutting in the fields and the tumble drying of greens

2. Chlorinated water alone isn’t enough to kill the pathogens.

3. Some varieties of spinach with textured leaves have greater potential for harboring pathogens than smooth-leaf varieties.

4. E. coli can paralyze pore closures (somata) on spinach leaves and allow bacteria into the plant.

5. Compost used inorganic operations can retain traces of live E. coli cells that can reconstitute under the right conditions.

6. Spinach and lettuce harvested on hotter days are more likely to create an environment for pathogen growth.

7. Lower product temperature, especially during transportation, lowers risk of bacterial growth.

8. Flies or other insects can excrete bacteria in their fecal droplets.

9.  It seems apparent that the E. coli bacteria is not absorbed by the roots into the plant structure.

OK, not much good news here. The only two areas that seemed hopeful was that some research on E. coli transmission found ozone gas is faster and more effective than chlorinated water at sanitizing leafy greens. And, although not mentioned until the last hour, irradiation of leafy greens can make food safer.

Bottom line – more work to do.
 

  • I’ve never heard of E. coli cells reconstituting back into a living bacterium. I actually was unaware that living things could do that. All my years of biology did not teach me about such a phenomena. Might you have a scientific reference from that conference that talks about this phenomena occurring in compost?
    Also, when you refer to “flies and other insects” excreting E. coli in their feces, which other insects? Which strain of E.coli?

  • Bill Marler

    “I’ve never heard of E. coli cells reconstituting back into a living bacterium. I actually was unaware that living things could do that. All my years of biology did not teach me about such a phenomena. Might you have a scientific reference from that conference that talks about this phenomena occurring in compost?”
    The data is not yet published, but the phenomena has been described in foods and other samples. The bacteria is not actually dead, but in a “dormant” state metabolically.
    1. Viable but non-culturable bacteria: their impact on public health
    http://www.ias.ac.in/currsci/nov252005/1650.pdf
    “The viability of a bacterial cell was traditionally determined by its ability to grow and produce colonies.However, in recent years, many studies have revealed the ability of both Gram-positive and Gram-negative bacteria to go into a viable but non-culturable (VBNC) state. In this state, bacteria are still viable and show metabolic activity
    and respiration, but cannot be shown as colony forming units by the conventional plate counts and hence remain hidden1.”
    2. Viable but non-culturable forms of food and waterborne bacteria: Quo Vadis?
    http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VHY-4CVX484-5&_user=4421&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_version=1&_urlVersion=0&_userid=4421&md5=70669e8045ab0219a3e5b0cb2b8b4664
    There is increasing evidence for a viable but non-culturable (VBNC) state in microbes, particularly in the stressing environment presented by modern foods with their varied pre-treatment and packaging strategies. This is a cause for concern because of evidence that microbial pathogens in such a state may retain their capacity to cause infections after ingestion by the consumer despite their inability to grow under the conditions employed in procedures for determining their presence in foods. Heavily stressed pathogenic species of bacteria in a VBNC or not immediately culturable state are potentially dangerous public health problems, particularly as stressed cells may be more virulent than well-fed bacteria. In this viewpoint article, I wish to focus on possible procedures for detecting such organisms and assessing their physiological state.
    “Also, when you refer to “flies and other insects” excreting E. coli in their feces, which other insects? Which strain of E.coli?”
    They looked at filth flies, blow flies and a couple other species. The preliminary positive results were mostly from filth flies trapped in the fields. They said additional studies are underway to identify the strains of E. coli excreted by the flies.