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Antibiotic resistances in the food chain

18/2010, 13.12.2010

BfR publishes two reports on the resistance situation for different groups of bacteria

The National Reference Laboratories for Salmonella and Antibiotic Resistance at the Federal Institute for Risk Assessment (BfR) tested Salmonella isolates from diagnostic submissions for antibiotics resistance and assessed them according to epidemiological criteria between 2000 and 2008. The isolates originated mainly from animals and foods but also from feeds and the environment. Of the 33,625 isolates, 48% were resistant to at least one and 35% even resistant to more than one class of antibiotics. For the isolates from livestock and foods the resistance is significantly higher. A second, representative study carried out in 2009 confirms the results for Salmonella and reaches similar results also for Escherichia coli and Campylobacter. "Resistances to pathogens in animals and foods are a serious problem in consumer health protection," said BfR President Professor Dr. Dr. Andreas Hensel. Infections with resistant pathogens can prolong or aggravate the course of diseases in humans. They can require hospital treatment and may even become life threatening in certain cases.

Salmonella are amongst the most frequent causes of food infections in humans. The so-called salmonellosis manifests itself mostly through nausea, vomiting and diarrhoea. Healthy people overcome this as a rule within a few days. In immunodeficient patients, senior citizens and children, the infection can also have a more serious course. This may require a treatment with antibiotics.

BfR has assessed the extent of resistances to antibiotics by means of epidemiological criteria which are valid throughout the EU. These allow the early detection of deviations from an unaffected bacteria population, the so-called wild-type population, and do not make any statement on the treatability of an infection. According to the assessment, Salmonella isolates of animals and foods show higher resistance rates for most of the antibiotically acting substances than those from the environment and feeds. Resistances to antibiotics classes which have already been used for some time in human and animal medicine, such as tetracyclines and amino-penicillins, were frequent. Resistances to antibiotics, which have been classified by WHO as particularly important for human medicine, can be detected in Salmonella of different origins, too. The resistant pathogens themselves are not the only problem, but also the fact that they can pass on the resistance to other pathogens is relevant. In this way the pool of resistance is extended and the risk for humans and animals increases, whereby watertight evidence for the transmission of these resistances to humans was so far only possible in individual cases.

In some cases resistances of Salmonella to the particularly important antibiotics groups were even very frequent. The serovars Salmonella paratyphi from chicken and chicken meat as well as Salmonella saint-paul from turkeys and turkey meat were 60 – 85% resistant to the group of quinolones and fluoroquinolones. These Salmonella serovars occur increasingly in these foods, but currently cause infections in humans only in a few cases. Resistances to cephalosporins of the third generation amount to 1.1% and were rare compared to the other substances; for individual Salmonella serovars there were, however, significantly higher rates.

The representative resistance monitoring of different pathogens in 2009 confirms the high resistance rates for Salmonella described for the years 2000 to 2008 and shows that they can also be detected in other bacteria of animals and foods. Resistances to fluoroquinolones are detected in particular in Salmonella and Escherichia coli of chicken but also in Campylobacter of chicken and veal, for up to two thirds of the isolates. Resistances to cephalosporins of the third generation were detected in more than 5% of the Escherichia coli isolates of chicken but also in some cases of isolates of veal.

In the two studies the resistance situation was analysed on the different levels of the food chain. The comparable resistance patterns of isolates of animals and from the meat of animals underline the probability that the pathogens can reach the meat in meat production. With the meat these resistant germs can in turn reach the consumers. The latter can prevent infections with the usual kitchen hygiene measures.

In order to prevent a further increase in resistances, the use of antibiotics should be limited to the absolutely necessary extent both in human and in veterinary medicine according to BfR. The monitoring of resistance development for pathogens and bacteria of the intestinal flora is a prerequisite to the risk assessment of antibiotic resistances. This monitoring but also measures to minimise the use of antibiotics in animals and in the food chain are part of the “German Antibiotic Resistance Strategy (DART)” of the German Government.

About the BfR

The Federal Institute for Risk Assessment (BfR) is a scientific institution within the portfolio of the Federal Ministry of Food, Agriculture and Consumer Protection (BMELV). It advises the Federal Government and Federal Laender on questions of food, chemical and product safety. BfR engages in research on topics that are closely linked to its assessment tasks.

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