Listeria monocytogenes, or Listeria for short, has been in the news a lot lately. Back in March, there was an outbreak of Listeria in Blue Bell Ice Cream and more recently, they found these buggers in Hy-Vee pasta salad and Jeni’s Ice Cream.

So what exactly is this “Listeria” organism?

Listeria monocytogenes is a species of bacteria found almost everywhere in our environment. One of the reasons why it’s so ubiquitous is that it is able to grow at low temperatures. In fact, this microbe can even grow at 0 °C, the freezing point of water. To provide contrast, most other bacteria prefer to live in cozy environments that range from 28 to 37 °C.

But before we go any further, how dangerous is this creature to our health?

While the media like to point out that the mortality rate of Listeria infections is as high as 60%, unless you have a compromised immune system (i.e. you’re elderly, pregnant, or have recently popped out of your mother’s womb), it’s extremely unlikely that you’ll ever become a statistic. Normal, healthy people have no problem fending it off — unless of course you ingest a big glob of it, in which case you’re on your own.

Nonetheless, Listeria still poses a major risk for the immunocompromised, and therefore is a real pain in the butt for people working in the food industry. See, because Listeria is so good at growing in low-temperature environments, refrigerating your food is not enough to prevent Listeria contamination. These guys are only destroyed by cooking food at high temperatures. This means that people who are immunocompromised should really stay away from non-pasteurized products and raw foods. As for (almost) everything else, well that’s fair game my immunocompromised friend!