Salad Doubts: Preventing and Controlling Pathogens on Produce
Cunningham, Aimee, Science News
Spinach's healthy reputation suffered a severe blow this fall. On Sept. 13, the Centers for Disease Control and Prevention in Atlanta learned that the raw leafy green was the prime suspect in a spate of virulent Escherichia coli infections. The next day, the Food and Drug Administration advised consumers not to eat any bagged fresh spinach. Two weeks later, the FDA announced that it had traced the tainted greens to one California company that bags spinach under several brand names. Fresh spinach from other suppliers soon began reappearing on store shelves and dinner plates. The outbreak's toll, according to the CDC: 3 deaths and more than 200 people sickened in 26 states and 1 Canadian province.
Federal and state officials have found the implicated bacterial strain in cow feces, water, and wild pigs at sites near the four suspected spinach farms in California, but they still don't know how the pathogen got to the greens. Officials continue investigating the incident, says Patti Roberts, a spokeswoman for the California Department of Health Services.
The spinach outbreak joins a growing list of health-related incidents tied to vegetables and fruits. According to the CDC, there's been an increase in such outbreaks in the past few decades.
The rise in produce-related illnesses can be linked to several factors. With people becoming savvier about their health, fresh-produce consumption has grown, notes Robert B. Gravani, a food scientist at Cornell University. During this time, however, more-dangerous microbial strains have emerged, he adds.
For example, the unusually virulent E. coli O157:H7 was first isolated in 1982, after an outbreak tied to contaminated hamburgers. A strain of that same bacterium was responsible for the spinach illnesses.
The food-distribution system also plays a role. "The production of fresh produce is much more centralized than it used to be, and [produce] gets distributed very widely and rapidly. There fore, one contaminated field may lead to a multistate outbreak that affects a large number of people," says Maria T. Brandl, a microbiologist with the U.S. Department of Agriculture's Agricultural Research Service in Albany, Calif.
Finally, detection strategies have improved, notes Larry R. Beuchat, a food microbiologist at the University of Georgia in Griffin. He suspects that many outbreaks of illness of unknown provenance that occurred 20 or 30 years ago "would today, with the technology available, be confirmed or at least linked to particular types of [contaminated] produce."
Preventing such contamination, from the farm to the dinner table, is the key to food safety, say many researchers. But farmers can't stop all contamination, and once tainted, many fruits and vegetables are difficult to clean. So, for the rare times when unwanted microbes make their way onto a farmer's crop, researchers are exploring new strategies and technologies to destroy these pathogens and to keep produce--and its consumers--healthy.
ON THE FARM Atypical vegetable's journey to market is full of potential contamination sources. Water that contains pathogens can come into contact with crops both during irrigation and in subsequent washing of harvested produce or its storage in ice. Animal feces can reach produce if domesticated or wild animals roam in the fields. Workers and equipment, such as bins or knives, can taint produce during the harvest or in later production steps.
To reduce the risk of contamination, the FDA in 1998 published recommendations for good agricultural practices (GAPs). This set of guidelines addresses issues that farmers must consider at various stages of the growing and harvesting process. For example, before applying manure to the fields, farmers must compost or treat it to remove pathogens.
"I honestly believe that if everyone was diligent about it, applying the principles of GAPs would ... go a very long way to preventing outbreaks," says Trevor V. …