Listeria evolved to live in your fridge

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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