Is Listeria monocytogenes lurking in your refrigerator?

A couple of weeks ago I reported on the tragic listeria outbreak that occurred as a result of contaminated Colorado canteloupe melons. The latest numbers are worse and worse; this listeria outbreak has now claimed 25 lives and sickened 123, making it the worst outbreak of food-borne illness since the 1970s. In fact, as I type this a House of Representatives panel has just announced the opening of an investigation, leaning over the shoulder of the Centers for Disease Control [CDC] which was already trying to find the source of the outbreak. Its mostly political posturing, of course, but when the House Energy and Commerce Committee calls a grower on the carpet, as they have with Jensen Farms of Colorado, you know the government means business.

What theyre trying to get to the bottom of, of course, is how such contamination occurred and how to prevent future episodes. As my previous article reported, food-borne illness is on the rise, and some experts are concerned that our increasing reliance on large-scale industrial farming may be at least partly to blame.

But truthfully, pointing fingers is not that easy. Listeria originates from waste animal or human used as fertilizer, and flourishes in water. Fruits and vegetables become contaminated with listeria when they touch soil, mud or water that contains the bacteria. At Jensen Farms, inspectors found listeria in runoff water that had flowed into a barn where cantaloupes were being processed and packed and then had gotten onto machinery. Since most farms use some type of waste as fertilizer, the risk has always been there, and its a question of how to keep food clean and bacteria-free while its being harvested, packed and shipped. But meats are also easily contaminated with listeria, as is anything packed in a canning or processing plant where listeria can get into the water or machinery.

So, knowing this, heres the operative question. Where does listeria typically lurk, and how can you keep these deadly bacteria out of your kitchen?

Here, 5 foods that can become contaminated and how to use them safely:

1. Canned and raw seafood.

When the FDA conducted a safety test of many types of food for listeria, the type that tested highest might come as a surprise to most people given the lack of press: smoked seafood. Of the 7,855 samples tested, 12.9 percent contained listeria. Preserved fish also tested high, as did raw seafood. Knowing this, I can tell you Ill only be buying my smoked salmon and canned smoked oysters from reputable companies, and Ill be throwing my salmon into pasta and other dishes rather than eating it cold on bagels. But thats just me.

2. Fruits of all kinds

Yes, canteloupes can pick up the listeria bacteria, as can other melons, but so can any fruit thats sprayed or washed with water containing listeria picked up from the soil. According to an FDA risk assessment for listeria, more than 11 percent of all fruits sampled tested positive for listeria. But heres the thing to remember, the listeria is on the outside of the fruit it doesnt spread throughout the flesh. So its not going to help to avoid certain types of fruits the damage to your diet and health would far outweigh the potential safety benefits, statistically speaking. [Sad stories are all over California about canteloupes left rotting in the fields and theres nothing wrong with those canteloupes.] What to do? Wash fruit as soon as you buy it with an antibacterial fruit and vegetable wash or, in a pinch, with antibacterial dish soap. Wash it again before you eat it, or better yet, peel it. But wash it even if you do peel it.

3. Foods that are refrigerated for long periods of time.

Another thing most people dont realize about listeria unlike most types of bacteria, it can continue to grow under refrigeration. So refrigerating food does not prevent the growth of listeria once its introduced. Cooking at high heat does kill listeria, so ready-to-eat foods that are eaten without cooking are a potential source. Cheese is one of these, but interestingly soft ripened cheese and semi-soft cheese tested higher than hard cheeses. One solution is to put cheese into cooked dishes, but if you like your cheese sandwiches, theres not a lot to be done.

4. Preserved and smoked meats.

Hot dogs, sausages, salami and all manner of preserved meats eaten cold are potential listeria culprits, according to the FDA. The sampling procedure found listeria in 6.4 percent of sausage samples, 4.8 percent of hot dogs sampled, and 6.5 percent of pâtes and meat spreads.

5. Root vegetables and ground-grown vegetables like squash

Vegetables that grow in the soil, like beets, carrots, and potatoes can come in contact with listeria in the soil, as can those that grow on low-lying vines like zucchini and other types of squash. But please dont let fear lead you to avoid veggies, which are healthiest foods in your diet. Instead, wash all veggies thoroughly and peel wherever appropriate. But wash before and after you peel, too just peeling doesnt cut it because the bacteria could be transferred on your hands.