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Antibiotic resistance of germs in meat production too high

08/2003, 01.04.2003

Third interim report of a BfR research project on resistance recording published

According to the most recent findings of experts from the Federal Institute for Risk Assessment (BfR), the rates of potential germs in beef, pork and poultry meat production that are resistant to antibiotics, are still too high. "In recent years we have observed a drop in the total number of resistant germs amongst Salmonella", says Dr. Reiner Helmuth, Head of the National Reference Laboratory for Salmonella in BfR, "but we are still seeing a high resistance level. We are very concerned that the rate of the germs, which are resistant at the same time to several antibiotics, has only fallen slightly. This applies both to germs from livestock sheds and to germs which come from foods". BfR is, therefore, renewing its demand for antibiotics to be used in animal stocks in an extremely restrictive manner.

Since 1999 scientists in the research project "Recording phenotypical and genotypical resistance traits in Salmonella and Escherichia (E.) coli isolates in animals, from food, feedstuffs and the environment" have monitored the development of resistances. Both germs are pathogens of so-called "zoonoses": the diseases which they trigger can be transmitted from animals to man. The germs studied in the project are isolated in state and private facilities and sent to the National Reference Laboratory for Salmonella. The control authorities of the federal states collect the samples both from stocks (of live animals) and from foods. In the National Reference Laboratory they are then analysed using modern molecular biology methods to determine their resistance properties.

Two opposite trends have been identified in the research project: Overall the share of Salmonella germs, which are resistant to only one active substance, has fallen markedly in cattle, pigs and poultry. By contrast, the number of multiresistant Salmonella germs has only dropped slightly in cattle and pigs. In the case of poultry it has even increased slightly. At the same time, the number of quinolone-resistant isolates has risen sharply in Salmonella and E. coli germs. This trend must be especially carefully monitored because quinolones are antibiotics which are used in human medicine to treat severe infectious diseases. They are, for instance, the preferred treatment for life-threatening Salmonella infections.

According to BfR, the reason for the increase in quinolone resistance is the widespread treatment of entire poultry stocks with fluoroquinolones in order to prevent the spread of diseases, a practice that should be abandoned for reasons of preventive consumer and health protection. This is because both the Salmonella and E. coli strains studied can trigger severe diseases in man. If they are resistant strains, then it may be very difficult to treat the diseases; isolated cases of treatment failure and fatalities have already been described.

What is also problematic in the opinion of BfR scientists is that over 90% of resistant germs found in cattle and pigs are resistant to five and more different antibiotics. This applies equally to E. coli and Salmonella strains. The carriers of this resistance are so-called "integrons". Integrons are genetic material. They are very mobile and act as a kind of "genetic taxi". They may "transmit" resistance genes both within their own species and across species. This brings with it the risk that the multiresistance may cross over to what had been non-resistant Salmonella or E. coli strains, perhaps even to other zoonosis pathogens.

The results to date of the research project show that there are no differences between the resistant germs isolated from foods and from animal stocks either in respect of their genetic properties or the incidence of resistance. This means that resistant zoonosis pathogens may reach man from the livestock sheds through food.

In the past, the predecessor institute to BfR, BgVV has repeatedly called on farmers, fattening plants and veterinary surgeons to only use antibiotics in animal production to treat animals which really are sick in order to control the spread of resistant germs (cf. bgvv press releases 04/1996, 07/1997, 04/2002). The Institute enjoys the support of the Federal Chamber of Veterinary Surgeons on this issue.

The third interim report of the research project "Recording phenotypical and genotypical resistance properties in Salmonella- and E. coli isolates from animals, food, feedstuffs and the environment" (in German) can be accessed on the homepage of BfR (www.bfr.bund.de) under the menu "Research" and downloaded as a PDF document.

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