A recent study by a graduate student at the University of Illinois looking at the ability of disease-causing bacteria to survive on fresh vegetables was not particularly comforting.
Meredith Agle, a graduate research fellow in the department of food science and microbiology, contaminated parsley with shigella, bacteria that cause diarrhea, fever, nausea, vomiting and cramps. Transmitted usually by the fecal-oral route, shigella sickens about 400,000 every year in this country. The latest big outbreak occurred among customers at a Chicago restaurant in 1999 who ate a bean salad: The parsley in the salad, grown in Mexico, was suspected to be the shigella carrier, Agle said.
Shigella is not the only food-borne bug: Some strains of E. coli, salmonella, listeria and the campylobacter bacteria are among the most common pathogens that can also be passed on via foods, cause illness and even death - especially in the very young, very old or in those who have weak immune systems. Food-borne illnesses account for about 325,000 hospitalizations and about 5,000 deaths every year in this country, according to the National Institute of Allergy and Infectious Diseases.
In her study, Agle washed some contaminated parsley with water for five minutes and some with a commercial wash that purports to kill bacteria, also for five minutes. The commercial wash was no more effective than water in removing the bacteria, she found. And although washing reduced the level of shigella, there was still enough to cause sickness.
Agle, whose study was presented at the Institute of Food Technologists meeting in New Orleans on June 26, also learned the bacteria could remain at contaminating levels for up to six days in the refrigerator; at room temperature, the shigella grew rapidly.
Agle said her findings should cause no one to panic: She contaminated her parsley with high levels of the bacteria, higher than you would probably find in a real-world contamination. Nev-ertheless, the fact that many of our fresh vegetables and fruit come from areas of the world with poor sanitation or water quality is cause for concern, she said.
Pregnant women or people with a compromised immune system should be careful about what they eat and make sure fruits and vegetables are carefully washed, Agle said.
Asked whether there is a specific length of time you should wash fruit and vegetables to get rid of pathogens, Martin Wiedmann, assistant professor of microbiology at Cornell University in Ithaca, N.Y., said there is no magic formula. And he acknowledged that certain fruit, such as berries, cant be washed for long periods without disintegrating.
Theres always going to be a risk… . In general the risk is minimal, but its not zero, Wiedmann said.
Wiedmann said the most important thing is for people to be aware and to practice good hygiene in the kitchen. It takes constant vigilance and common sense, he said.