Vegetables May Include Bacteria That are Resistant to Antibiotics

Salad is popular with people who want to maintain a balanced and healthy diet. Salad varieties are often offered for sale ready-cut and film-packaged. It is known that these types of fresh produce may be contaminated with bacteria that are relevant from the point of view of hygiene. A working group led by Professor Dr. Kornelia Smalla from the Julius Kühn Institute (JKI) has now shown that these bacteria may also include bacteria that are resistant to antibiotics.

“We have to get to the bottom of these findings”, said Professor Dr Georg Backhaus, President of the Julius Kühn Institute. Antimicrobial-resistant bacteria are known to occur in manure, sewage sludge, soil and bodies of water. “This worrying detection of these kinds of bacteria on plants is in line with similar findings for other foods”, adds Professor Dr Dr Andreas Hensel, President of the German Federal Institute for Risk Assessment (BfR). “We are now assessing as a matter of urgency what this finding means with regard to the health risk for consumers.”

Link: The transferable resistome of produce

For the purpose of analysis, the working group headed by Professor Smalla purchased mixed salads, arugula and cilantro in German supermarkets. The samples were then analyzed in order to determine the total quantity of transferable antimicrobial resistance genes (the researchers use the term “transferable resistome”) in Escherichia coli, a mostly harmless intestinal bacterium, on these foods. In their analyses, the experts focused on the part of Escherichia coli bacteria that are resistant to the active substance tetracycline. This is because tetracycline antibiotics are used in livestock farming, where they can promote the development and propagation of resistant bacteria in organs such as the intestine. These bacteria as well as part of the antibiotics are excreted and then find their way onto the fields via organic fertilizers like manure. Smalla says that “the results of the comprehensive tests clearly show that a wide variety of transferable plasmids – gene carriers in bacteria that occur outside the chromosomes – have been found with resistance genes in the E. coli from fresh produce. Each of these plasmids carries resistance to multiple classes of antibiotics. E. coli bacteria with these properties have been found on all three analysed foods.”