What causes E coli on lettuce

Multi-resistant germs on raw vegetables and lettuce

BRAUNSCHWEIG / BERLIN. It is well known that lettuce that has been cut and wrapped in foil can be contaminated with hygiene-relevant germs.

A working group from the Julius Kühn Institute (JKI) together with colleagues has now proven that this also includes germs that are resistant to antibiotics (mBio 2018; 9 (6): e01300-18).

For the investigations, the researchers led by Khald Blau from the JKI bought mixed salads, rocket and the aromatic plant coriander in German supermarkets. The samples were then examined to determine the entirety of the transmissible antibiotic resistance genes in E. coli on these foods.

"Worrying Evidence"

The scientists concentrated on the part of the E. coli bacteria that are resistant to the active ingredient tetracycline.

Because tetracycline antibiotics are known to be used in animal husbandry, where they can promote the development and reproduction of resistant germs in the intestines of livestock.

A considerable variety of transferable plasmids with these resistance genes were found in the E. coli on all three tested foods, it says in the communication.

"This worrying evidence ranks among similar findings for other foods," said Professor Andreas Hensel, President of the Federal Institute for Risk Assessment (BfR), quoted as saying. What this means for the health risk for consumers is now being assessed as a matter of priority.

In general, based on the current study, the BfR recommends washing raw vegetables, lettuce and fresh herbs thoroughly with drinking water before consumption in order to minimize the risk of the ingestion of pathogens or antibiotic-resistant bacteria.

Washing cannot safely remove germs

Pregnant women and immunocompromised people should also avoid eating pre-cut and packaged salads as a precaution to protect against food-borne infections and instead prepare salads themselves from fresh and thoroughly washed ingredients shortly before consumption.

However, washing cannot safely remove any pathogens or antibiotic-resistant bacteria that may be present on the plant-based foods.

Therefore, in rare individual cases, it is necessary that especially immunocompromised persons, according to the instructions of their treating physicians, heat vegetables and fresh herbs sufficiently (i.e. at least two minutes to 70 ° C inside the food) before consumption, the Federal Office reminds in the message. (eb)