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Matt Soniak
What is Salmonella & how did it get in my tomatoes?
by Matt Soniak - June 18, 2008 - 12:05 PM

salmon.jpgSalmonella is a genus of enterobacteria (Kingdom: Bacteria, Phylum: Proteobacteria, Class: Gamma Proteobacteria, Order: Enterobacteriales, Family: Enterobacteriaceae, if you’re a stickler for detail), named after Daniel Elmer Salmon, an American veterinary pathologist, who is credited as its discoverer (some sources say it was actually his research assistant, Theobald Smith, that did the discovering.) The Salmonella genus contains a motley crew of two species, several sub species and more than 2,000 serovars (groupings of microorganisms based on their cell surface antigens).

The bacteria cause salmonellosis, an infection that bestows upon you the joys of diarrhea, abdominal cramps, nausea, vomiting, fever and headaches. These symptoms usually appear within 8-72 hours after infection and can last 4-7 days. The source of infection is usually tainted food; after ingestion, Salmonella binds to the wall of the intestine, penetrates it and then starts to wreak havoc (a more in-depth explanation, if you don’t mind some technical terms, can be found here).

So how did this stuff get into tomatoes?

tomato-Salmonella.jpgWhile the FDA hasn’t been able to find the source of the contaminated tomatoes or figure out how they became tainted, we can take some educated guesses about the cause of contamination. Since the bacteria’s preferred residence is the intestinal track of humans and animals, food usually gets tainted through contact with feces. The Center for Science in the Public Interest (CSPI) suggests a number of ways Salmonella could have gone from feces to tomatoes to you during the current outbreak:

• Contaminated water was used to irrigate the tomato crops

• Contaminated animal manure was used as fertilizer

• Somewhere, someone involved in the process of picking, packing, processing and preparing the tomatoes didn’t wash their hands after using the bathroom

• Farm or wild animals spread the bacteria onto tomato crops either with their own feces or feces they tracked in from somewhere else (the 2006 E. coli problem with spinach was traced to a pack of wild boars that stepped in contaminated cow manure and brought it into a spinach field when they grazed there)

Once Salmonella was on the tomatoes (which isn’t too much of a problem, since they get rinsed with chlorinated water after harvest), it could have gotten inside through cuts or scars on the skin or through the scar left when tomato is picked from the vine.

As for the source, that’s a bigger problem. Pick a vegetable, any vegetable, from your fridge. Do you know where it was grown? Probably not unless you’re buying it at a farmers’ market directly from the folks who grew it. There’s a fairly complex supply chain between the farm and your fridge (example diagrams here and here); the processors along that chain are only required to know who they bought from and who they sold to, and most don’t know who is further up or down the chain.

If you’ve got a burning question that you’d like to see answered here, shoot me an email at flossymatt (at) gmail.com. Twitter users can also make nice with me and ask me questions there. Be sure to give me your name and location (and a link, if you want) so I can give you a little shout out.

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Comments (15)
  1. My fiance and I both got salmonella poisoning on the same night, hours after eating lunch together at a mall restaurant. It was very, very unpleasant. Could it have been their food? It’s hard to know for sure, but the restaurant closed up abruptly about three weeks later.

  2. It is highly unlikely that you got salmonella poisoning from that restaurant if you ate it the same night you got ill. It usually requires 24 hours for the bacteria to multiply to a population where it would make you ill. Exceptions are where food is so infested with bacteria that they have secreted toxins, then eating that contaminated food would induce illness upon hours of consuming.

  3. When we can we eat tomatoes again?!

  4. I second Lisa’s comment – I want my tomatoes back!

  5. As a server, I was instructed to tell guests that we were not currently serving tomatoes due to the outbreak.
    Apparently the preventative measures were lifted at some point last week because after I finished telling a table their food would not have tomatoes as described, their food came out with tomatoes on it again. They looked a little scared.
    THAT was embarrassing and odd.

  6. Ew. I never want to read about ‘the joys of diarrhea’ again. Great article, though. I had no idea how the E. coli outbreak got started; sometimes I wish I weren’t so curious.

  7. Maybe it wasn’t salmonella then, dee, but the listed symptoms seem to be dead on

  8. i knew my aversion to tomatoes would pay off one day. hopefully this will be over soon.
    also sounds like another good reason to buy locally and know where your food comes from.

  9. We have a really great farmer’s market in my town, so I buy everything I possibly can there. It’s cheaper than grocery stores, and supports the local economy. Good thing, too, because I haven’t been watching the news, and had no idea about the tainted tomatoes.

  10. Why can’t I get the theme song from “Attack of the Killer Tomatoes” out of my head?

  11. I guess we could stop importing and let our, better regulated, farmers plant the crops that we consume.

    Stop farm subsidies and we can eat clean, cheaper food.

  12. Last May I got something similar to salmonella, but my doctor never did any tests to determine the exact cause of my illness. So, I’ll never know for sure what made me so sick. I got violently sick a few hours after eating pizza and remained violently sick for a week. I had a fever, chills, nausea, painful abdominal cramps, and I couldn’t eat or drink without it coming back out in 30 minutes or less. When I walked up the stairs in my house, I had to sit and rest for 10 minutes because it made me so exhausted. I finally went to my doctor after 6 days and he put me on Cipro to help clear my stomach of any bacteria that was causing my illness. It was another two days when my fever broke and that made feel 100 times better even though my stomach was still having issues digesting food. I finished my one week supply of Cipro and my stomach was still having issues, but it was nowhere near as bad as before. So, I just dealt with it and assumed my stomach needed more time to recuperate. I slowly figured out which foods didn’t upset my stomach, which turned out to be peanut butter & jelly sandwiches and rice. For the most part I ate that for the next 3 weeks with some experiments in eating other foods that either went well or horribly wrong.

    Now things are pretty much back to normal, but for some reason I can’t eat ice cream anymore. I can eat cheese, fettucine alfredo, mac & cheese, and drink milk, but if I eat ice cream it makes me sick. Any thoughts?

  13. Staci – The same thing happened to me after being on an antibiotic. I was never lactose intolerant before the antibiotic. Luckily, I can eat cheese, yogurt, and whipped cream, and milk only if it’s been heated (i.e. cream sauce) but I can’t eat ice cream, drink milk or have cream cheese.

    I’m not a biologist/med student/whatever, but I wonder if maybe the antibiotic killed off too much of the “good” bacteria in my stomach and now that’s why I can’t digest the lactose? I don’t know…

    But to bring this back on topic – I also knew my aversion to tomatoes would pay off!

  14. Staci and Melodye: If you developed lactose intolerance from an antibiotic, I highly recommend taking an acidophilus supplement. You can get them at Wal-Mart, and they should fix up your stomach within a fairly short time (they’re also good for preventing gas). I had lactose intolerance for a while as a kid, and drinking milk with acidophilus (and eating lots and lots of yogurt) got my stomach straightened back out in no time.

  15. Before I eat pizza, or cream sauces, I have to take 2 or 3 Lactase tablets for my lactose intolerance. It’s a brand of lactase enzyme supplement. It seems to work.

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