Lettuce has been known to harbor E. coli O157.

• A. False
• B. Not known
• C. Sometimes
• D. True

Answer: (D)

Leafy greens like lettuce can harbor pathogenic E. coli O157:H7. There have been documented outbreaks and investigations linking lettuce and other fresh greens to illnesses caused by this organism, showing that contamination can and does occur. E. coli O157:H7 is a Shiga toxin–producing strain that can be present in fecal material and can reach lettuce through contaminated irrigation water, soil, manure, or handling at growing, processing, or packaging stages. Because it has a low infectious dose, even small amounts on the leaves can cause illness, making lettuce a plausible vehicle for this pathogen. That combination of possible contamination pathways and the documented outbreaks is why the statement is true.