Tainted Tomatoes and Food Safety

The recent salmonella outbreak associated with tainted tomatoes made red Roma tomatoes, red round tomatoes and plum tomatoes hard to find in supermarkets.

While this outbreak is the nation’s largest salmonella outbreak from tomatoes, and since April, more than 550 people have been infected by this specific salmonella saintpaul strain (this is a sub-type of the big family of salmonella bacteria), I’d like to put things in perspective.

Outbreaks related to a single source of contamination get a lot of media attention, and serious action is taken to identify and eliminate the foods suspected to be contaminated, yet more common sources of food-borne illness don’t get a lot of coverage or thought.

Here’s a fact about salmonella infections you might not have known, and this is a quote from the CDC’s website:

“Every year, approximately 40,000 cases of salmonellosis are reported in the United States. Because many milder cases are not diagnosed or reported, the actual number of infections may be thirty or more times greater”

If the past three months were typical, an estimated 3150 reported cases of salmonella per month would be unrelated to the tainted tomatoes, and the tainted tomatoes would be the cause for only about 5 percent of salmonella cases reported since the outbreak started.

And the bigger picture, again from the CDC:

“An estimated 76 million cases of foodborne disease occur each year in the United States. The great majority of these cases are mild and cause symptoms for only a day or two. Some cases are more serious, and CDC estimates that there are 325,000 hospitalizations and 5,000 deaths related to foodborne diseases each year. The most severe cases tend to occur in the very old, the very young, those who have an illness already that reduces their immune system function, and in healthy people exposed to a very high dose of an organism. “

How do the bacteria get into produce?

Fresh fruits and vegetables don't naturally contain disease causing bacteria.

Produce can become contaminated in the field by contaminated water, by wild and domestic animals’ fecal material, or by improperly composted animal manure. It can also be contaminated post-harvest if the workers handling, storing, transporting and preparing the produce don’t practice good hygiene.

Fresh produce can become contaminated with disease-causing bacteria when it’s in contact with raw animal products such as meat, poultry or seafood or eggs. This can happen before you buy the produce, in your shopping cart, or in your home—your fridge, counters, cutting boards and knives can all carry harmful bacteria if they’re not properly cleaned after coming in contact with raw animal products.

Indeed, the CDC warns that raw foods from animal origin the most likely to harbor disease causing bacteria:

“Raw foods of animal origin are the most likely to be contaminated; that is, raw meat and poultry, raw eggs, unpasteurized milk, and raw shellfish. Because filter-feeding shellfish strain microbes from the sea over many months, they are particularly likely to be contaminated if there are any pathogens in the seawater. Foods that mingle the products of many individual animals, such as bulk raw milk, pooled raw eggs, or ground beef, are particularly hazardous because a pathogen present in any one of the animals may contaminate the whole batch. A single hamburger may contain meat from hundreds of animals. A single restaurant omelet may contain eggs from hundreds of chickens. A glass of raw milk may contain milk from hundreds of cows. A broiler chicken carcass can be exposed to the drippings and juices of many thousands of other birds that went through the same cold water tank after slaughter.”

What should we do?

I really like the guidance given by Jorge M. Fonseca and Sadhana Ravishankar in the American Scientist (you can read the full text here, and see the helful illustration)

“Fortunately, there are several steps one can take to avoid getting sick from tainted produce. The single best piece of advice is still to wash fruits and vegetables thoroughly before eating them—a practice that can result in a ten-fold reduction in surface contamination. Wash hands with soap before beginning, but just use lukewarm tapwater and a clean cloth or scrub brush on the food…Consumers have much more control over their exposure to foodborne pathogens when cooking at home. In preparing fruits or vegetables that will be eaten raw, cut away any damage and the area around the stem scar; these are often sites of microbial colonization. Also, remember that many instances of foodborne illness caused by fresh produce actually begin with cross-contamination from raw meat. Foodborne pathogens are much more likely to survive and thrive in uncooked meat than in fruits or vegetables, which explains why it is much safer to eat raw produce than to eat raw meat. Hands, surfaces and kitchen tools should be washed thoroughly with soap before and after preparing food, and it is prudent to wash hands frequently while cooking—most especially after handling meats or using the toilet.”

They conclude with some more words of advice I truly agree with

“Overall, it's important to put the risk of eating produce in a larger context. Fresh fruits and vegetables are no riskier than other fresh foods as sources of foodborne pathogens, and eating a salad is certainly safer than driving to work. Furthermore, many forms of produce confer remarkable health benefits on people who eat them. Given these benefits, avoiding fresh fruits and vegetables is probably riskier than enjoying them—even if you still eat unwashed fruit with grubby fingers.”

The time honored advice of washing carefully—hands and produce—is the simplest and most effective way to avoid most food-borne disease. Bear in mind that reduction of the amount of harmful bacteria--and not absolute elimination of them in food--is enough to avoid illness with most bacteria (including salmonella) as a relatively large load of ingested bacteria is necessary to cause most disease in healthy people.

In the meantime since many retailers and restaurants have temporarily pulled all large tomatoes off their shelves and menus—even though many region’s tomatoes have been cleared from suspicion of being contaminated--I feel for the tomato growers whose produce is going to waste.
Ayala