Mett, eggs and Co: rapid test for the detection of Salmonella in food

Mett, eggs and Co: rapid test for the detection of Salmonella in food

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Detect Salmonella in food with a rapid test

Food poisoning caused by Salmonella occurs again and again. Especially with certain risk groups, it can lead to serious illnesses. A common source of infection is raw meat such as mett. A new rapid test should help to track down the pathogens within a short time.

No one is immune from infection with Salmonella, but infants, toddlers, seniors and people with compromised immune systems are particularly affected. So far, it has taken several days to detect the pathogens in food. According to a current report, a new rapid test by Fraunhofer researchers will detect the germs in less than eight hours in the future.

Severe illnesses possible

As the Federal Office for Consumer Protection and Food Safety (BVL) explains on its website, Salmonella are bacteria whose metabolic products can trigger acute intestinal inflammation, Salmonellosis, in humans. According to the Robert Koch Institute (RKI), this is one of the most common bacterial diseases in humans.

Symptoms of a Salmonella infection can include watery, persistent diarrhea, vomiting, fever and abdominal pain.

According to the BVL, the symptoms can last for several days. As a rule, the disease heals after a few days even without medical treatment, but especially in small children and the elderly, the diarrhea can quickly lead to life-threatening dehydration of the body or to a general infection of the body.

"Therefore, a doctor should be consulted immediately in these cases," write the experts.

Bacteria enter the body through infected food

The bacteria get into the gastrointestinal tract by eating infected animal foods such as eggs, egg products such as mayonnaise, milk, poultry, seafood and raw meat and trigger the typical symptoms.

The problem: According to the Fraunhofer-Gesellschaft, it has so far taken up to four days to detect salmonella in animal products using classic microbiological methods. However, this process takes too long for food manufacturers - they cannot wait for the result until their goods are delivered. As a result, there are always expensive recall campaigns.

Therefore, significantly shorter verification procedures are required. Together with SELEKTIS GmbH, a research team at the Fraunhofer Institute for Cell Therapy and Immunology IZI-BB, part of the Bioanalytics and Bioprocesses division in Potsdam, is developing a rapid test that can be used to determine whether food is contaminated with Salmonella in less than eight hours.

Enrichment process significantly reduced

So far, a lot of time has been required for the enrichment of the bacteria: microbes that are only present in small quantities are grown and multiplied in a liquid nutrient medium overnight, so that a sufficiently high number of bacteria is available for subsequent detection.

According to the information, this process has taken about 18 hours to date, three more days are required for the selective enrichment and incubation of the Salmonella in additional liquid media, the streak-like spreading of a bacterial culture on agar plates and for the serological test.

The project partners have already succeeded in reducing the first lengthy enrichment process from 18 hours to four to six hours. This goal was achieved with the help of an innovative method for cultivating the germs:

“We managed to do this by creating a rapid culture with growth conditions optimized for Salmonella. Through a subsequent innovative, optimized enrichment method, we can increase the concentration of the bacteria so that we can then detect them after only a few hours using molecular biological methods, ”explains Dr. Harald Peter, scientist at Fraunhofer IZI-BB.

“For this, the DNA of the Salmonella is reproduced and then automatically detected. To do this, we extract the DNA of the Salmonella and multiply it so that it can be detected after another 30 minutes. For the rapid test, we design the molecules that specifically detect the DNA of the Salmonella, ”says the scientist.

It is crucial to obtain the highest possible concentration of Salmonella DNA for sensitive detection within a short period of time. Using fluorescent dyes, the researchers can mark the duplicated DNA and detect it using capture molecules.

Test can also be transferred to other pathogens

Molecular biological detection methods are already used in laboratories today, but rarely in fully automated form, and so far not in food diagnostics. To achieve this, Dr. Peter and his team have a system that automatically carries out all processes that were previously carried out manually, such as cultivation, enrichment, molecular-biological duplication and detection.

In the future, all the necessary components will be integrated into a compact device measuring around 40 by 40 centimeters. With a few molecular biological special processes, the researchers at Fraunhofer IZI-BB can, for example, do without certain DNA purification steps and thus significantly simplify and accelerate the process.

“According to the food hygiene regulation, a sample of 25 grams of meat must not contain a single Salmonelle. The new rapid test must therefore be able to detect a single bacterium within a total of six to eight hours, i.e. within one work shift. Another task is to differentiate the Salmonella from other microorganisms, ”says Dr. Peter.

The advantage: According to the information, the test can also be transferred to other food pathogens. All that is required is to adapt the catcher molecules to other organisms on the computer using gene databases. (ad)

Author and source information

This text corresponds to the specifications of the medical literature, medical guidelines and current studies and has been checked by medical doctors.

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  6. Gerold

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