Conversation with a Microbiologist about E. coli O157:H7
In a recent conversation with Dr. Laurie Achenbach, a microbiology professor at Southern Illinois University, she discussed her thoughts on contamination of lettuce and spinach with E. coli O157:H7. The following is a synopsis of some of her comments:
- If grazing cows are too close to a spinach or lettuce field, cow manure can easily contaminate the field with E. coli O157:H7. The manure can even get dry enough to become airborne and land on leaves or soil.
- Microscopic amounts of cow manure contaminated with E. coli O157:H7 can “hide” in the crevices of lettuce and spinach leaves. Even multiple commercial washings, where there is no friction used, will not get all of the microscopic amounts of manure off.
- Consumers should always wash off “pre-washed” lettuce and spinach under running water while gently rubbing the leaves. Each leaf should be washed separately. The combination of friction and running water will remove most of the E. coli-contaminated manure.
- People at risk of developing serious complications from an E. coli O157:H7 infection should probably not eat raw spinach and lettuce because there can be no guarantee that the leaves are not contaminated with E. coli O157:H7.
- Even though research has indicated that E. coli O157:H7 can reside in as well as on lettuce and spinach leaves, Dr. Achenbach thinks it is highly unlikely that the recent E. coli outbreaks linked to spinach and lettuce were a result of E. coli O157:H7 in the leaves. E. coli O157H7 is not a plant pathogen and will not colonize inside of a lettuce or spinach leaf. E. coli O157:H7 on the leaves is the greatest danger, according to Dr. Achenbach.
