Lettuce's Roots Lure Salmonella
A sugar-like substance attracts the dangerous pathogen, scientists say
THURSDAY, Oct. 11, 2007 (HealthDay News) -- Salmonella, a bacteria that causes tens of thousands of cases of foodborne illness each year, may be especially attracted to lettuce by the prospect of something sweet.
The bug is apparently enticed by a sugar-like substance lying in the leafy green's roots, say a team of Dutch scientists.
They believe the results may help one day find new ways to prevent infection with the potentially deadly germ, but others are not so sure.
"It's a laboratory study and it can't be generalized to anything else," said Dr. Douglas L. Hurley, a professor of internal medicine at the Texas A&M Health Science Center College of Medicine and an infectious disease doctor at Scott & White. "It can't be generalized to lettuce growing in a field by a long shot."
"The great majority of human outbreaks of salmonellosis come from chicken or eggs, so the question is what kind of public health import would this have," added Philip Alcabes, an epidemiologist and an associate professor at the School of Health Sciences of Hunter College, City University of New York in New York City.
Indeed, salmonella infection usually comes from eating contaminated ground beef, eggs and pork and, increasingly, poultry, rather than produce.
Some 40,000 cases of salmonellosis are reported in the United States each year. However, because milder cases are not diagnosed or reported, the U.S. Centers for Disease Control and Prevention estimate that the actual number of infections may be 30 or more times greater. Some 600 people die each year after being infected with salmonella. Infection can cause diarrhea, including bloody diarrhea, in humans.
But foodborne illness in general, especially from E. coli, another bacteria, is being increasingly traced back to produce. And in March, the U.S. Food and Drug Administration issued voluntary guidelines for food industry processors to minimize contamination of ready-to-eat produce.
Reporting online Oct. 11 in The International Society for Microbial Ecology Journal, a team at Wageningen University in The Netherlands maintain that salmonella infections from produce are also becoming increasingly common. In these cases, infection can come from poor hygiene among workers or contamination via soil or water tainted with animal manure.
In this paper, the researchers reveal that salmonella bacteria move towards the roots of the lettuce, apparently attracted by a sugar-like carbon source located there. When the bacteria gets close, the molecule triggers a genetic signal which, in turn, triggers bacterial reproduction.
While government and industry are actively looking for ways to prevent salmonella infection in the field and during the processing stages, there are ways people can protect themselves at home:
- Make sure ground beef and other meats, as well as eggs, are well-cooked before you eat them.
- Wash raw fruits and vegetables with soap. Pay particular attention to leafy greens as there are lots of crevasses and cracks where bacteria can hide.
- Don't chop vegetables on the same block where you just made beef hamburgers or prepared other meat. Keep raw meat separate from ready-to-eat foods.
- Refrigerate leftovers promptly.
- Avoid bruised produce such as tomatoes.
- Make sure all cooking utensils including meat thermometers and cutting boards are thoroughly cleaned with soap and hot water after you've handled them.
- Wash your hands regularly with soap and hot water.
- Drink only pasteurized milk, juice or cider.
For more information on salmonella, visit the U.S. Centers for Disease Control and Prevention.