Tomatoes & Salmonella

Salmonella, a bacterium, causes about 40,000 cases of salmonellosis illness annually, with symptoms including fever, nausea, vomiting, bloody diarrhea and abdominal pain, according to the Centers for Disease Control and Prevention. Some 80,000 cases of salmonella infections linked to tomatoes, primarily those eaten in restaurants, may have occurred between 1990 and 2006, the CDC’s MMWR Weekly estimates.

Considerations

Salmonella normally lives inside animal intestines, and the path by which it reaches tomatoes involves several vectors, including runoff, manure and wild animals, policy researcher Ryan Hagen writes in the daily web magazine Slate. Asymptomatic cows, pigs and chickens can shed the bacteria in their waste solids, which may be used to fertilize fields. Runoff from pastures or waste lagoons can dirty irrigation sources. And wild animals can track livestock manure into tomato fields. Bird, animal and insect droppings can also contaminate produce, notes the University of Florida IFAS Extension.

Theories

In addition to vectors that contaminate the surface of tomatoes, which may also include improper personal hygiene of workers who harvest or pack the produce or handle it in restaurants, scientists are debating whether the bacteria colonize the internal parts of the tomato plant. Soil microbiology researcher Max Teplitski and colleagues at the University of Florida, in a review of the literature, note evidence that salmonella in infected soil or seeds can spread throughout the plant.

Outbreaks

In 2008, 1,442 Americans, including many in Texas, were sickened by an outbreak of the rare Salmonella Saintpaul strain originally blamed on raw plum, Roma and round tomatoes but later linked to jalapeno peppers grown in Mexico. A 2006 outbreak was traced to two tomato fields in Florida, notes the CDC. Twelve multistate outbreaks have been blamed on tomatoes since 1990, based on reporting by state public health departments.

Types

Producers rinse their harvest with chlorinated water to remove salmonella, but enough can remain to make you sick, Hagen notes. A sliced tomato purchased at a supermarket or eaten at a restaurant or a picked tomato whose skin is punctured can have bacteria inside and thus may be riskier than a whole, on-the-vine tomato that you can wash yourself.

Prevention

Although salmonella does not cause decay in tomatoes, avoid damaged fruit anyway, because it is more likely to contain pathogens, Teplitski recommends. Store tomatoes in a cool, dry place. To prevent surface bacteria from infiltrating the fruit tissues, do not soak vegetables. Wash tomatoes in food-grade detergents that lack harmful chemicals but not in bleach. When slicing tomatoes, cut out the stem scar, the rough area on the top of the fruit, which can harbor more bacterial.