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  • From: KAKerby AT aol.com
  • To: market-farming AT lists.ibiblio.org
  • Subject: Re: [Market-farming] manures/GAP training
  • Date: Wed, 3 Mar 2010 13:35:32 EST

Here is a link to the paper they cited in class:
 
 
Here is the title of that same paper, in case the above link gets butchered:
Survival of Escherichia coli O157:H7 in soil and on carrots and onions grown in fields treated with contaminated manure composts or irrigation water, by Mahbub Islam, Michael P Doyle, Sharad C Phatak, Patricia Millner, and Xiuping Jiang, Food Microbiology 22 (2005) 63-70
 
 
Merely searching Google on "survival of escherichia coli soil" came back with a bunch of different studies, so there's quite a few to choose from.
 
As to your point about 'not all E coli are dangerous, and in fact most are beneficial', yes that is absolutely correct and that was discussed in class.  The general point is that, soil does NOT naturally carry E coli as part of the normal microbiological flora.  Only soils which have been pooped on (or irrigated with contaminated water) within the last 200 days, will carry E coli of any variety.  If Farmer Joe's production systems allow for E coli of any variety to get into his soil, then by definition at least some of his fields could have been contaminated by E coli from the more dangerous strains.  In other words, if Farmer Joe's fields can be contaminated by poo, then it's only the luck of the draw whether that poo will have come from an animal which carried the most dangerous strains.  The whole point of the class was to show us how that contamination can occur, how long that contamination can last, and what we can do to minimize it.  Ironically, pastured animals were just one of the significant threats.  Employee personal hygiene was a huge factor because merely going to the restroom then coming back to pick crops could introduce contamination to otherwise clean fields.  We don't have employees here other than myself, so that part of things didn't rate very high on my personal radar because I can change my own handwashing habits as needed.  But the animal manure really hit home because that's something that we use a lot of.  If folks have no animals, no animals upstream, and 50 employees, their risk assessment and risk management needs will be a lot different than mine.
Kathryn Kerby
Frog Chorus Farm
Snohomish, WA
 
 
In a message dated 3/3/2010 9:32:41 A.M. Pacific Standard Time, organic87 AT frontiernet.net writes:

On Mar 2, 2010, at 5:27 PM, KAKerby AT aol.com wrote:

The science behind the new guidelines were based on recent studies which have tracked how long E. coli lived either in the soil or on surfaces.  They provided details from one of the studies, which tracked soil, onion and carrot contamination, on four test plots per vegetable along with a control plot.  If you want the exact name and authors of the study, I can provide that but the title was pretty long. 

If you have a link to the full study, I would be interested to see it. I do have a batch of questions, many of them having to do with whether they ran this in a number of different areas, climates, soil types, types of farm management, etc.; if so, what if any was the variation in results? if not, are they following up the preliminary study with additional studies checking these variables, are any of those results in, and what do those show? (It's interesting that they apparently referenced "recent studies" but provided details from only one study. Did the others have significantly different results? If so, do they have any idea what factors produced the difference? -- While it's possible this was just a result of their having only minimum time for the presentation, it can happen that only the studies that back up what the presenter wants to happen to be mentioned, while multiple studies with other results don't get referenced, or don't get published in the first place.)


I also have another major question I haven't seen addressed in all of this: did they test specifically for pathogenic eColi, or just for E Coli in general?  

Everyone in this discussion (unless I missed something) has just been saying "E coli, E coli". Most strains of E Coli are neutral or even beneficial. If "10 cells of E Coli" generally made anyone deathly ill, we'd all be dead. Your gut is full of E Coli right now -- every mammal's is -- and is in fact structured to function in that state. And one of the things I was told repeatedly at the FDA meeting was that there is considerable doubt that the presence of the "indicator organisms" generally checked for (faster and cheaper, I gather, than testing for specifically pathogenic species) genuinely indicates anything about the presence of pathogens.

The fact that the presence of E Coli usually does not mean the presence of pathogens most likely explains the fact a number of others in this discussion have pointed out: that hordes of people are every day eating produce grown in non-sterile conditions, including produce grown in fields that deer walk into, birds fly over, mice inhabit, etc.; but significant illness is actually quite rare. The major outbreaks that hit the news aren't due to the pathogenic bacteria being all over the place: they're due to a small amount of pathogen that may have originally been on only a few plants or in one animal being mixed in processing plants with huge amounts of other meat or produce, packaged (in the case of greens) in conditions conducive to its growth, and shipped all over the country; so that one corner of a spinach field can make people sick in twenty states. (I don't know if the pathogen in that particular spinach was ever even definitively traced to contamination of the field, as opposed to the possibility of its having been spread by a worker at the farm, or even a worker at the processing plant.)


-- Rivka; Finger Lakes NY, Zone 5 mostly
Fresh-market organic produce, small scale



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