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Ask The RD: E. coli and Lettuce?

How do we get E. coli from lettuce, and how can we prevent it?


I keep hearing about people getting E. coli from lettuce. I thought E. coli came from beef. Can you explain what E. coli is and why lettuce is a problem?


Last year, more than 250 people got sick in two big outbreaks of E. coli bacteria linked to romaine lettuce, one in April and another in October (CDC 2018). There are many types of E. coli bacteria, only some of which cause foodborne illness. Shiga toxin–producing E. coli (STEC) bacteria, especially STEC 0157, are common in the United States and cause about 265,000 infections every year (CDC 2016). E. coli is no fun. It causes severe diarrhea and can lead to kidney failure.

You are right that E. coli is often linked to beef, especially ground beef. That’s because E. coli lives in the intestinal tract of cattle. If intestinal contents or feces get on meat when cattle are slaughtered, the meat can become contaminated. Cooking a steak or roast usually kills bacteria on the outside; however, when you grind contaminated raw meat, the bacteria becomes distributed throughout. That’s why undercooked ground meat like hamburger is associated with E. coli.

Outbreaks have also been linked to lettuce, prepared salads, spinach and other leafy greens (CDC 2018a). The greens can become contaminated if they are grown near cattle. The bacteria can also come from contaminated water or from people handling greens after touching that water. Because we eat greens raw, bacteria aren’t destroyed.

The good news is there is plenty you can do to avoid getting E. coli. Here are some of the precautions advised by the U.S. government (CDC 2018b). These are especially important for kids and older people, who are at higher risk.

  • Wash hands frequently and thoroughly (try reciting the ABCs to make sure you wash, scrub and rinse for long enough).
  • Wash fruits and vegetables well, under running water.
  • Cook meat thoroughly. Use a food thermometer to check temperature. Cook beef steaks or roasts to 145 degrees Fahrenheit and ground beef to 160 F.
  • Avoid cross-contamination. Keep counters, cutting boards, utensils and hands clean.


CDC. 2016. Escherichia coli (E. coli). Accessed Dec. 3, 2018: cdc.gov/ecoli/pdfs/CDC-E.-coli-Factsheet.pdf.

CDC (U.S. Centers for Disease Control and Prevention). 2018a. Reports of selected E. coli outbreak investigations. Accessed Nov. 1, 2018: cdc

CDC. 2018b. Escherichia coli (E. coli) prevention. Accessed Nov. 1, 2018: cdc.gov/ecoli/ecoli-prevention.html.

Sanna Delmonico, MS, RDS, CHES

"Sanna Delmonico, MS, RDN, CHE, is an associate professor at the Culinary Institute of America where she teaches food safety and nutrition. She previously led programming for the CIA Healthy Kids Collaborative and the CIA-Harvard Healthy Kitchens, Healthy Lives Continuing Medical Education Conference. Prior to joining the CIA, she was an instructor at Santa Rosa Junior College where she co-coordinated the dietetic technician program. Sanna develops delicious, seasonal recipes and writes about food and nutrition for publications, including IDEA Fitness Journal. She lives in Napa, California, and is a home winemaker."

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