Multi-Resistant Germs Detected In Ready-To-Eat Salads

A federal research institute has detected antibiotic-resistant bacteria in supermarket lettuce. This is how you can protect yourself.

Packaged salad products are popular as a lunchtime snack. However, the already cut, washed and plastic-packaged ready-to-eat salads are not as healthy as they appear at first glance: it is nothing new that the ready-to-eat products are often contaminated with germs. Scientists from the Julius Kühn Institute (JKI) have even found bacteria that are resistant to antibiotics on packaged salads and fresh herbs from the supermarket. This means that antibiotics are ineffective in the event of an infection with the bacteria.

For the investigation, the working group led by Prof. Dr. Kornelia Smalla bought 24 different mixed salads, rocket and fresh herbs in German supermarkets. The investigations focused on the resistance of Escherichia coli bacteria to the antibiotic tetracycline. The researchers found coliform bacteria that are resistant to the antibiotic tetracycline in all of the samples they examined.

But how do the bacteria get into the ready-to-eat salad? The researchers suspect that residues of the drug tetrazyline get onto the fields via animal excrement in the form of liquid manure as fertilizer. Tetracycline is often used in animal housing. Resistant germs should also get onto the fields via animal excrement.

Germs with several antibiotic resistances on ready-to-eat salads

In a second step, the researchers examined whether the germs are also resistant to other antibiotics. A whole range of drugs was ineffective against some bacteria – among other things, the bacteria were also resistant to penicillin, amoxicillin and ampicillin. These antibiotics are extremely important for the treatment of seriously ill patients.

An exciting partial result of the study: “The bacteria, which are harmless in themselves, could transfer their resistance genes to other pathogenic bacteria in the human intestine,” explains Kornelia Smella’s working group in the specialist journal “mBio”. This is known as “horizontal gene transfer”. In nature, horizontal gene transfer enables bacteria to adapt rapidly to changing environmental conditions When a patient is treated with antibiotics, bacteria that have incorporated such transferrable resistance genes into their genome have an advantage and outgrow their less-equipped competitors “, according to the JKI.

The Federal Institute for Risk Assessment (BfR) makes the following recommendations:

Wash raw vegetables, lettuce and fresh herbs thoroughly before consumption to minimize the risk of ingesting pathogens or antibiotic-resistant bacteria.

However, even washing alone cannot reliably remove any pathogens or antibiotic-resistant bacteria that may be present on plant-based foods. People with a weakened immune system should, after consulting their doctor, cook vegetables and fresh herbs sufficiently before eating them – at least two minutes at 70°C inside the food.

Pregnant women and people with a weak immune system are best advised not to eat pre-cut and packaged salads. In the past it was found that these finished products posed an increased risk of germs.

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