Even though the United States has the safest food supply in the world, there are occasional outbreaks of food borne illnesses.  One of the most recent was salmonella in spinach.  Now one researcher is lighting the way toward a solution.

E. Coli
Escherichia coli (E. coli) is a bacterium that lives in the intestines of all animals. Normally, the bacteria have a good purpose. They suppress the growth of other harmful bacteria and help the body synthesize some vitamins. But certain strains of E. coli can make people sick. Signs of infection typically develop within three to four days. Patients may experience severe, bloody diarrhea and stomach cramps. In most cases, the symptoms go away within 5 to 10 days.

One particular strain of E. coli, O157:H7, produces toxins that damage the lining of the intestine and can cause serious symptoms. In some cases, infection with this type can lead to hemolytic uremic syndrome (HUS), a condition characterized by destruction of red blood cells and kidney failure.

The Centers for Disease Control and Prevention estimates about 73,000 cases of E. coli O157:H7 infection occurs each year. More than 2,100 people are hospitalized for treatment and 61 people die.

E. Coli and Fresh Produce
In Fall, 2006, E. coli made headlines during a widespread outbreak associated with fresh spinach. Between August 26 and September 16, 205 cases were reported in 26 states. More than 100 people were hospitalized; 31 people developed HUS and three died.

With more Americans seeking healthy diets and quick/easy meal preparation, convenience packages of produce are big business in this country. The FDA estimates Americans spend $12 billion on fresh-cut produce each year. But the recent spinach outbreak highlights the importance of finding a way to detect and eliminate potential E. coli contamination.

Health experts say cooking usually kills E. coli and other bacteria that can cause foodborne illness. But some fresh produce is eaten raw. Rinsing removes most of the surface contaminants. However, researchers have found that cutting raw produce breaks the plant’s natural protective barrier by exposing and opening up the veins. Harmful bacteria can enter the veins and travel inside each piece of produce. Once inside, the bacteria can no longer be washed away. At that point, heating is the only way to kill the germs.

Scientists at Purdue University have developed a technique to study how E. coli enters lettuce leaves. They isolated DNA from bioluminescent bacteria (bacteria that naturally glow) and combined it with a strain of E. coli O157:H7. When alive and healthy, the genetically engineered bacteria glow.

The researchers took their engineered bacteria and put them in a dark place to stop them from growing and giving off light. Then they placed a stalk of celery in a solution containing the bacteria. As the contaminated solution traveled up through the veins of the celery, the researchers could see the bacteria start “glowing” inside the stalk. More importantly, the bacteria began to glow very brightly, indicating they were becoming more active. The experiment showed that not only did the bacteria get inside the celery stalk, it was able to remain alive, and thus cause infection.

The bioluminescent bacteria can help researchers looking for a way to kill the bacteria and decontaminate the produce. Food Microbiologist, Bruce Applegate, Ph.D., says if a treatment process works, the bacteria should stop glowing and scientists will quickly be able to visualize and confirm the results. The researchers are also testing laser technology to detect many types of foodborne bacteria. Yet another Purdue study is looking at the use of chlorine dioxide gas to kill bacteria and disinfect produce.

Currently, there is no way to completely guarantee that fresh produce will be safe from bacterial contamination. In fact, on August 29, 2007, a California produce company recalled bags of fresh spinach found to be contaminated with another foodborne germ, salmonella.
Applegate recommends cooking produce whenever possible. Produce that’s to be eaten raw should be washed thoroughly and kept in the refrigerator until just before serving time.

For general information on E. coli:
Centers for Disease Control and Prevention, Division of Bacterial and Mycotic Diseases, http://www.cdc.gov/ncidod/dbmd
FDA, Center for Food Safety and Applied Nutrition, http://www.cfsan.fda.gov
Gateway to Government Food Safety Information, http://www.foodsafety.gov
National Institute of Allergy and Infectious Diseases, http://www3.niaid.nih.gov
Partnership for Food Safety Education, http://www.fightbac.org

For information on Hemolytic Uremic Syndrome:
National Kidney and Urological Diseases Information Clearinghouse, http://kidney.niddk.nih.gov

BIBLIOGRAPHY

“About Foodborne Illness,” Washington , DC : Partnership for Food Safety Education, downloaded from website (http://www.fightbac.org), August 23, 2007.

“The Bad Bug Book,” College Park : FDA, Center for Food Safety and Applied Nutrition, downloaded from website (http://www.cfsan.fda.gov), August 23, 2007.

Doyle, M., and M. Erickson, “Reducing the Carriage of Foodborne Pathogens in Livestock and Poultry,” Poultry Science, June 2006, Vol. 85, No. 6, pp. 960-973.

“Escherichia coli O157:H7,” Atlanta: Centers for Disease Control and Prevention, Division of Bacterial and Mycotic Diseases, downloaded from website (http://www.cdc.gov/ncidod/dbmd), August 23, 2007.

“Foodborne Diseases: E. Coli,” Bethesda : National Institute of Allergy and Infectious Diseases, downloaded from website (http://www3.niaid.nih.gov), August 23, 2007.

“Guide to Minimize Microbial Food Safety Hazards of Fresh-cut Fruits and Vegetables,” College Park : FDA, Center for Food Safety and Applied Nutrition, downloaded from website (http://www.cfsan.fda.gov), August 23, 2007.

“Hemolytic Uremic Syndrome,” Bethesda : National Kidney and Urological Diseases Information Clearinghouse, downloaded from website (http://kidney.niddk.nih.gov), August 23, 2007.

“How the FDA Works to Keep Produce Safe,” FDA Consumer, March-April 2007, Vol. 41, No. 2, pp. 12-19.

Mylonakis, Eleftherios, M.D., Ph.D., et al., “Escherichia Coli Infections,” eMedicine, updated May 25, 2006, downloaded from website (http://www.emedicine.com), August 23, 2007,

“Nationwide E. coli O157:H7 Outbreak: Questions and Answers,” College Park: FDA, Center for Food Safety and Applied Nutrition, downloaded from website (http://www.cfsan.fda.gov), August 23, 2007.

Rangel, Josefa, et al., “Epidemiology of Escherichia Coli O157:UH7 Outbreaks, United States, 1982-2002,” Emerging Infectious Diseases, April 2005, Vol. 11, No. 4, pp. 603-609.

“Surveillance for Foodborne-Disease Outbreaks – United States, 1998-2002,” MMWR: Morbidity and Mortality Weekly Report Surveillance Summaries, November 10, 2006, Vol. 55, No. SS-10.

Research compiled and edited by Barbara J. Fister, Medstar Television