Listeria evolved to live in your fridge

Cold cuts are pretty much delicious little hostels for listeria—a bacteria that can cause serious food poisoning, and even kill vulnerable populations like babies, the elderly, and the sick. That's why doctors advise pregnant women to not eat them, and why the CDC suggests that older people reheat their "cold" cuts to 165 degrees before eating them.

But I've long wondered: Why are listeria able to get such a foothold on a food product that's already been cooked, and that is generally stored in refrigerators? Shouldn't those two factors impede bacterial growth?

I took my question to my favorite Scary Disease Girl, Maryn McKenna. Turns out, this is another case where we have evolution to thank for a public health predicament. Listeria has actually adapted to survive at refrigerator temperatures, McKenna told me. So, all it takes is some improper handling of the meat, somewhere along the production chain, and a little listeria can bloom—inside your fridge—into a potentially serious problem.

Further proof that god intended bologna to be fried.

Also thanks to Evidence Matters!
Image: Some rights reserved by Kent Wang

Maggie Koerth-Baker is the science editor at BoingBoing.net. She writes a monthly column for The New York Times Magazine and is the author of Before the Lights Go Out, a book about electricity, infrastructure, and the future of energy. You can find Maggie on Twitter and Facebook.

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Anonymous

Temperatures need units. Preferably sensible units.
Apreche

You know another great way to get Listeria? Drinking raw milk.

Yeah, looking at you Mark.
- Anonymous
  
  Actually raw anything, not just milk. Why does fresh milk always get such a bad rap?
  And did you read the article? Pasteurized milk will have the same problem with listeria. Welcome to earth!
Anonymous

This is an honest and serious question. Does this only apply to meat? What about soy-based vegan deli slices, like Tofurkey?
dragonfrog

“the CDC suggests that older people reheat their “cold” cuts to 165 degrees before eating them”

You don’t have to eat them at that temperature – you just have to heat them to that temperature a bit before eating them. Heat them, put them on a ceramic plate to absorb the heat, get the bread ready, the mustard, the pickles, bring a beer up from the basement, then make your sandwich with the cold cuts properly cold again.

Once the bacteria are dead from heat, cooling the meat doesn’t instantly bring them back to life.
Alvis

I recently started slicing my own meats and cheeses – I wonder if that helps things any, if the bacteria only multiply on the surface?
- Anonymous
  
  just so you know, most food poisoning actually occurs in the home. health inspectors regularly inspect places like grocery stores and restaurants.
yosemite

I am half Sicilian and I disapprove of this message.

Nothing will keep me away from my sopressa and mortadella.
- Flaminica
  
  Yeah brother. The day I’m too feeble to eat calabrese the way God intended is the day you can push me out to sea on an ice floe.
- Anonymous
  
  LOL. Good call Yosemite!
  
  Strange that in countries such as Spain and Italy, when they use traditional methods, the food is not only fantastic looking/tasting, but also you virtually never hear of food poisoning. IIRC, Salami was widely used for that very reason, whereby meat could be stored safely for long periods of time.
  
  The problems seem to come when big business is involved.
frankieboy

think I’ll sit down and have a peek a BB while I have lunch…. oh for cryin’ out loud
any problems with chips? just to make it perfect?
Anonymous

I’ve been wondering for a while now, why don’t fridge makers put UV lights on the inside that turn off when the door is open? That should take care of unwanted bacteria growth right?
- Anonymous
  
  How would you know if the UV bulb was burned out?
BB

That looks positively disgusting without even contemplating microbes. Bleh.
gwailo_joe

The cold cuts shown seem a little bland for my taste. . .Where’s the hot coppa? Spicy turkey?

No, after rechecking the photo: those meats are all totally edible. . .just too monochromatic.
millie fink

I agree, BB–cold cuts, hot dogs, sausages–who KNOWS what’s in that crap? Ugh!

Actually, that’s why I don’t eat ANY industrial meat. The fecal matter, the microbes, the chemicals, the antibiotics, the growth hormones, and on and on. Ugh!

Sad (though grateful) to read above that this problem can infect tofu too. I’ll be sure especially sure to cook it thoroughly from now on.
- Anonymous
  
  I did not know that about tofu. I will also cook mine more thoroughly from now on.
Chocolatey Shatner

Just another one of many reasons I am happy to be celebrating my nineteenth year of vegetarianism this month
nashley85

I just got a REALLY bad case of food poisoning from Subway–and the only things on my sandwich were cold cuts, cheese, and condiments. A woman I work with (who has advanced degrees in nutrition and is recently pregnant) told me that listeria may have been the cause, and that she is now definitely staying away from deli meats while she’s pregnant after hearing that I got sick. It’s real and it’s out there! Maybe the lesson here is to not get your cold cuts at a fast food restaurant…
daen

Maggie, I think what we’re actually seeing here is natural selection. Fast forward a bit, and you could call it evolution. I’m just not sure that human being and their refrigerators will be around long enough for listeria to carve out a particularly stable ecological niche from this adaptation.
billstewart

That’s “cooked, refrigerated, and containing nitrites and other preservatives”. If it’s scary for you to eat, it ought to be scary for bacteria.

But living at refrigerator temperatures isn’t a big evolutionary jump – bacteria do actually manage to live in cooler climates, and in places that have winters, or in San Francisco in the summer time, and in bodies of dead animals that are at ambient temperature instead of still being warm-blooded. The main difference is that they grow more slowly at lower temperatures.
Anonymous

I refuse to give up my Boars Head EverRoast!
incubeth

According to CDC website and FDA Bug Book… this is not a “real threat” at all. A minimal risk, at best, and a way to get people to get all paranoid. I bet the handful of cases each year are due to people mishandling their own food or trying to eat it way past it being safe to do so.

“The vast majority of cases are sporadic, making epidemiological links to food very difficult.” (Source: FDA Bad Bug Book)

I think having some common sense comes into play, here.

On a personal note, My OB told me (just last week) that unheated deli meat was “just fine”, but advised against raw fish.

(I had sashimi, anyway. I enjoyed every minute of it! They DO have babies in Japan, right?)
- sally599
  
  Invoking the CDC and the FDA doesn’t make your comment accurate. Listeria is a threat to a small group of people, here we’re talking about the elderly not the pregnant. You could say that Legionnaire’s disease isn’t a real threat either because it only targets old people and most of us are fine taking showers or walking past air conditioners. To me anything that kills people is a threat. Only a handful of people die from shark attacks but you’d probably pull your kid and yourself out of the water if you saw a fin coming. I don’t think this article was meant to stop anyone from eating their bologna but to point out some of the unique adaptions occurring—it’s not a cook your lunch meat now freak out so much as a wow isn’t this neat type of article.
  - badtux
    
    Funny, http://www.americanpregnancy.org/pregnancycomplications/listeria.html says that listeria *is* a threat to the pregnant.
    
    Regarding health inspectors, depends on your locale and the amount of money health inspectors in your area make via legal vs. extralegal means. (I..e, are health inspectors in your area so poorly paid they accept bribes?). In some places, I suspect that no health inspector has been by there since my mother was an infant…
Anonymous

If I worried about everything people said was bad for you or could kill you I would be dead from starvation already.
jphilby

Ask not for whom the stomach sours…
Neural Kernel

http://www.youtube.com/watch?v=ZBiboVzi2VI
You’ve got problems when a bear won’t even STEAL your food!
Anonymous

@ anon, Yes, tofu is just as at risk as any other form of protein if stored improperly. That’s why in in the refrigerator cases in the supermarket.
pinehead

Further proof that god intended bologna to be fried.

Hell yes. I remember eating fried bologna sandwiches when I was a kid. My mom would cut a slice halfway across each disc before frying. That way, when the bologna drew-up as a result of cooking, the slice would open up and look like PAC-MAN. I loved my PAC-MAN bologna sandwiches.
Anonymous

Dogs can eat rotten meat, their own crap, or toilet paper and be fine.

We disinfect every surface imaginable and our digestive systems fall apart when we drink milk or consume the wrong microbe, and our kids swell up like balloons if they get in the same room with a peanut. Our species is doomed.
- Susan Oliver
  
  Dear, dear Anon – you realize that dogs are different from humans, right?
  
  They’ve evolved to be able to eat a rather different diet than we have. Their shorter GI tract, for one, enables them to eat raw meat infected with salmonella with a much, much lower risk of contracting disease. The food stays in long enough to extract nutrients, but not long enough to colonize the harmful bacteria.
  
  Is there a do-it-yourself kit to test for these bugs? Suddenly I’m curious about that 3-day-old Alps prosciutto in my fridge. Not because I’m paranoid – just intrigued.