How does E. coli contaminate leafy greens? I hear that it came from tainted irrigation water, but vegetables are grown in manure. Why should a little non-potable water contaminate them? I don’t understand the mechanism.
Thanks for your help,
Rob
Poop in water system + water sprayed on plants = poop on plants. E. coli lives in poop and moves with it. That’s it, basically.
The manure used as compost/fertilizer is clean, because the heat created in the composting process kills e. coli - you don’t just scoop raw manure on your lettuces. You let it sit around getting itself nice and decomposed and safe first.
Not to mention the fact that manure is rarely, if ever, used anymore on large-scale commercial farms. Smaller, organic farms use it, but by and large, commercial farming uses synthetic fertilizers.
One additional problem is that the deadly form of E. coli is a specific strain found primarily in cows raised in large scale cattle farms (O157:H7). This E. coli strain was selected to survive in a very high acid content found in grain-fed beef (through natural selection, not specifically engineered to do so).
Cows that eat their natural food source (grasses and hay) have a much less acidic stomach environment. When we ingest this new strain of E. coli, our acidic stomachs do not kill it off, so it makes us very sick. The runoff from these cattle farms gets into the produce, creating the food posioning epidemics.
Cite:
[ URL=http://www.sciencenews.org/pages/sn_arc98/9_19_98/food.htm]Science News article
Fixed coding- sorry!
The idea that forage feed significantly reduces the amount of O157:H7 in cattle is still under debate. (Wikipedia link,scroll down to the “relationship with industrial agriculture” bit).
While grain feeding may have selected for acid resistance in general, it isn’t responsible for O157:H7 picking up the ability to produce Shiga-like toxin.
I am under the impression that most bacteria are ubiquitous in a random sample of dirt. Therefore spinach was always taking E. coli up through its roots. Is it fair to say that the recent problem is caused solely by this new strain? Also, why isn’t it more common? Will we see the spread of this strain in the near future?
Thanks for your help,
Rob, who is late for work
While dirt isn’t sterile, obviously, E. coli doesn’t live in the soil or water very well for very long. For that reason finding E. coli somewhere is a marker for fecal contamination.
Something that hasn’t been discussed in the press about these incidents is another source of the E.coli. I’ve read “improved hygiene” mentioned once or twice, but that’s it. The fact is, contamination by human feces is a very real problem.
Let’s say the spinach is harvested by migrant farm workers who are paid by the bushel- it is in their best interest to harvest as much spinach as quickly as possible taking the fewest breaks possible. Let’s also say that there is one porta-potty on the side of a large field and if a worker has to take a bathroom break they’ll need to walk 500 yards back and forth. It’s certainly possible that porta-pottys aren’t being used every time.
The government researchers examining the fields that grew the contaminated spinach in California had several theories about why it happened. One theory was based on runoff from a cattle feedlot uphill from the fields.
Surely migrant workers wouldn’t just drop trou in front of everybody and pinch off a loaf right there in the middle of the spinach field.
Uh … wait a second … I just remembered back when my friend Stan and I were both about 14 and were working construction for my dad, and Stan had to poop really bad one day; he went behind a big palette of cinderblocks that was next to an adobe wall, squatted down, and pooped right there. (Later, in a nauseatingly hilarious incident, some deviant went back and scooped the surprisingly large result up in a Gatorade bottle and presented it to him as a gift. Heh heh … good times, good times.)
So maybe it IS possible. But we didn’t have an outhouse at ALL! At least, not that we could find in the short amount of time he had available. And it was in a secluded corner of the job site, not in the middle of a spinach field. Unless spinach grows on big trees … man, I’m glad I only ever had to be an underground-utility laborer and not a spinach-picker. At least we had an abundance of large palettes and trenches when the outhouses weren’t around.