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Tomatoes and salmonella: What to look out for

BY ERICA MARCUS | erica.marcus@newsday.com

11:00 AM EDT, June 24, 2008

Since mid-April, there have been 383 reported cases of salmonellosis in 30 states, the culprit being Salmonella Saintpaul, an uncommon strain of the bacterium. Now that Long Island has had its first reported case of salmonellosis-by-tomato, I've seen an uptick in the number tomato-safety questions I get asked, to wit:

Which raw tomatoes are safe to eat and which are not? All cherry, grape or on-the-vine tomatoes are safe to eat. The only implicated tomatoes are the large, round ones (sometimes called beefsteak) and the egg-shaped plum tomatoes (sometimes called Romas) that are usually used to make sauce.

Now, even with these two types, the vast majority of growing regions have been exonerated. Any tomato, even the beefsteaks and plums, from New York, California, all the Northeastern states, Israel, Canada and the Netherlands, is safe. Right now the FDA is zeroing in on southern and central Florida (the northern counties have been given a clean bill of health) and Mexico.

Bottom line: if you are sure that the tomato you have is not from Florida or Mexico, go ahead and eat it. And if it's a cherry, grape or on-the-vine tomato, it doesn't matter where it's from; you can eat it. (More specific information can be found at www.cfsan.fda.gov, the Web site of the FDA's Center for Food Safety and Applied Nutrition.)

What should I do with tomatoes I already have? If they are of the unsafe types (see above), do not eat them. The market where you bought them might refund your money; otherwise, throw them out.

Can't I just wash a suspect tomato to get rid of the Salmonella? No. Washing is not a surefire method of removing the bacterium. And there is no way to know if the bacterium has already gotten inside the tomato.

What about peeling the tomato? No dice. The act of peeling a contaminated tomato can easily spread the Salmonella to the inside. Not to mention that the inside might already be contaminated.

What about cooking the tomatoes? You'd think that would do it, but the FDA advises against it. The problem is that while the heat may kill the Salmonella on or in the tomatoes, everything the tomato touches on its way to becoming sauce gets contaminated: the sink, the cutting board, the knife, the lip of the pot, your hands, etc. Throw out the tomatoes.

Are canned tomatoes and tomato products safe? Anything in a can, a bottle or a jar that is stored in a nonrefrigerated section of the market is fine: canned tomatoes, tomato sauce, ketchup, tomato soup, shelf-stable salsa. These products are commercially processed in a way that kills any and every possible contaminant. But tomato products that are displayed in refrigerated cases -- perishable salsa and gazpacho, for example -- may not have been pasteurized. If you can't confirm that the tomatoes they were made from are of the safe variety (see above), give them a pass.

Why are certain varieties safe? Is there something about their genetic makeup that makes them resistant? No. It all has to do with where the tomato was grown. Certain states and countries specialize in different types of tomatoes. Until the FDA can pinpoint exactly where the infection occurred, it is advising consumers to avoid the types of tomatoes grown in the areas that have not been ruled out.

What about local farm tomatoes? If you've read this far, you will have figured out that local tomatoes -- which are still more than a month in the offing -- are going to be perfectly safe, as are the tomatoes you'll harvest from your own garden.

But two years ago, during the spinach E.coli outbreak, skittish, irrational consumers shunned our local spinach, even though all the contaminated spinach came from one county in California. It's important to remember that there is nothing intrinsic about a head of spinach or a tomato that makes it susceptible to bacterial infection. What matters is where it was grown and how it was handled.

How would a tomato become infected with Salmonella in the first place? Salmonella is a type of bacterium that live in the intestinal tracts of humans and animals and is transmitted, initially, through contact with feces. You can understand why chicken meat (or eggs) might become infected -- just try to keep birds from interacting with their own poop -- but a little harder to see how a tomato would become a victim. The culprit is usually water. Crops come into contact with water when they are irrigated, fertilized, washed and processed. If that water came into contact with infected animal feces -- not hard to imagine if livestock is being raised nearby -- then it can pass the Salmonella onto the crops.

Does Salmonella have anything to do with salmon? No. The bacterium Salmonella enterica var. Choleraesius, which causes hog cholera, was discovered in the late 19th century by an American veterinary pathologist named Daniel Elmer Salmon and his colleague Theobald Smith. Thereafter the entire genus was named Salmonella.