JKI warns Resistant bacteria found in many ready made salad products!

Resistant pathogens detected in finished products with salad

Raw food and salads are healthy and important for a balanced and low-calorie diet. Many manufacturers now offer the "salad to go". Finished, packaged and with portioned dressing, the healthy fast food variant offers a healthier alternative to many other ready meals. Unfortunately, one recent study found that these products often contain germs - some even with antibiotic resistance. What are the health hazards of these products and who would rather do without them? An expert team clarifies!

A research team led by Professor Dr. Ing. Kornelia Smalla from the Julius Kühn Institute (JKI) investigated the bacterial load in finished products with lettuce, which are consumed unheated. It has often been found that such products may be contaminated with hygiene-relevant germs. Researchers looked into this finding and looked at the risks posed by lettuce. The results describe the team as worrying. Not only pathogenic germs were found - among the proven pathogens were also antibiotic-resistant bacterial strains. The study was recently published in the journal "mBio" of the American Society for Microbiology.

Finished fresh produce from the supermarket, such as mixed salads, may contain antibiotic-resistant intestinal bacteria. (Image: Dani Vincek / fotolia.com)

Are finished fresh products a health risk?

It has long been known that antibiotic-resistant bacteria are found in manure, sewage sludge, soil and water. Now, the JKI team showed that such germs can also get into unheated finished products. Especially finished raw food products and salads are affected. On the basis of this finding, the Federal Institute for Risk Assessment (BfR) recently issued a warning message, which should inform about the correct handling of such products.

Which salads were examined?

The working group around Professor Smalla examined several mixed ready-made salads, packaged rocket and coriander from different supermarkets. In many products the gut germ Escherichia coli was found. This bacterium has numerous pathogenic strains and is more often the causative agent of severe infectious diseases with diarrhea as its leading symptom - such as EHEC. According to the research team, among the bacteria found were a considerable variety of bacterial strains with resistance genes.

How do resistant intestinal germs get into the vegetables??

The JKI researchers explain that in livestock antibiotics are often used with the active ingredient tetracycline. The constant use promotes the formation of resistance in the intestinal bacteria of the animals. The increasingly resistant germs are excreted by the animals and thus get into the manure. This in turn fertilizes the plants that are used for ready-made salads.

Salad germs can pass on their resistance to human intestinal germs

According to Smalla, the resistant plasmids found in the pathogens are particularly worrying. These are hereditary traits that can pass bacteria on to other strains. This process is called horizontal gene transfer. There is a danger that plasmids of resistant germs will transfer their resistance to other pathogens in the human intestine.

Federal Institute clarifies the right way to deal with

"In general, consumers should thoroughly wash raw food, lettuce and fresh herbs with drinking water before eating to minimize the risk of ingesting pathogens or antibiotic-resistant bacteria," the Federal Institute for Risk Assessment said in a press release.

These people should better avoid finished fresh produce

"Pregnant women and persons whose defenses are weakened by old age, pre-existing conditions or medication should, as a precautionary measure, refrain from consuming pre-cut and packaged salads to protect against food-borne infections," recommends the Federal Institute for Risk Assessment. Of course, one should therefore generally refrain from salad. It would be better to prepare salads from fresh and thoroughly washed ingredients.

Immunocompromised individuals should be extra careful

By washing alone, however, not all germs could be removed. "Particularly immunocompromised persons should, according to instructions of their treating physicians, sufficiently heat vegetables and fresh herbs before consumption," said the Federal Institute. At least a temperature of 70 degrees Celsius inside the food must be achieved over a period of two minutes, so that all germs are killed. (Vb)