Bacteria resistant to antimicrobials found on broiler meat not a new development
An investigation carried out by the Association for Environmental Protection and Nature Conservation (BUND) has caused a stir: on 10 out of 20 bought meat samples, ESBL producing bacteria were found, while two samples were contaminated with MRSA pathogens. “The detection of such resistant bacteria on broiler meat does not constitute a new insight”, Professor Dr. Dr. Andreas Hensel, President of the Federal Institute for Risk Assessment (BfR), explains. As part of the Zoonosis Monitoring Programme 2009, the BfR analysed the resistance situation for zoonotic pathogens and commensal bacteria. Out of 629 analysed broiler meat samples, 22.3 percent contained bacteria suspected to be MRSA. In representative studies conducted in 2009, a low proportion of commensal E. coli suspected to produce ESBL was also detected in productive livestock and foods. For example, in 5.9 percent of E. coli isolates from broilers and 6.2 percent of E. coli isolates from broiler meat, resistance to Cephalosporins of the third generation was found which is an indication of the formation of ESBLs. However, such bacteria were also detected on turkey meat, pork and in faecal samples of veal calves. With its press release of 13 December 2010, the BfR drew attention to these findings and published its report on the subject.
Methicillin-resistant Staphylococcus aureus (MRSA) are bacteria which in humans can cause wound infections, inflammation of the respiratory tract and other infections. They are resistant to certain antimicrobials. So far MRSA has been found predominantly in hospitals. A special type of MRSA, the so-called livestock-associated (LA) MRSA, is also found in production animals. To the present day, only few cases have been described in which an MRSA infection in humans could be attributed to food consumption. In the few known cases, the food concerned had been contaminated by infected persons.
ESBL-forming bacteria can destroy some antimicrobials such as Penicillins and Cephalosporins of the third and fourth generation by means of enzymes. In consequence, they are resistant to these substances. ESBL stands for extended-spectrum beta-lactamases. These pathogens have been found not only in hospitals but also in animals. The enzyme can be produced by harmless intestinal bacteria or pathogenic bacteria. Since ESBL-forming bacteria have also been detected in production animals, an infection of humans with ESBL-forming pathogens via food is possible in the opinion of the BfR. How important the contribution of the infection sources food, production and domestic animals as well as livestock in agriculture is for the ESBL associated illness in humans cannot be evaluated on the basis of the currently available data. Nevertheless, already at this point in time the latest biomolecular insights clearly suggest that ESBL-forming bacteria from animal production do pose a risk to human health. A special problem is the transferability of the genes responsible for the antimicrobial resistance between different bacterial groups. Resistance genes which enter the human organism via harmless intestinal cultures can, once in the intestine, be transferred to other bacteria which in case of an infection are then more difficult to treat.
As part of the Zoonosis Monitoring Programme 2009, it was shown that 22.3 percent of broiler meat samples and 42.2 percent of turkey meat samples contained MRSA. Meat from pigs (15.8 percent) and calves (12.9 percent) was also contaminated with MRSA. Of the investigated E. coli and salmonella isolates from broiler meat, approximately 5 to 6 percent were resistant to Cephalosporines, a finding that is usually attributable to the formation of ESBLs. Moreover previous studies of the BfR had repeatedly drawn attention to the presence of resistant bacteria, especially salmonella, in meat.
The bacteria on the meat predominantly originate from livestock production. The competent authorities of the states (Laender) have been finding MRSA and, increasingly, ESBL forming E. coli and salmonella in livestock on farm for some years now. During slaughter, these bacteria can be transferred from the animal to the meat.
The BfR welcomes a package of measures which was presented by Federal Minister Aigner. The BfR recommends that the use of antimicrobials in animal production be critically reviewed, especially with regard to antimicrobials that have special significance for human medicine. Animal husbandry and management must be improved in such a way that the animals remain healthy, so that treatment is not required in the first place. The slaughter process must be improved in a way which ensures that the transfer of bacteria from animals to food is further reduced. The BfR recommends to consumers to only eat meat after it has been thoroughly cooked or fried and to prevent the transfer of bacteria to other food by observing the rules of kitchen hygiene.
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. The BfR conducts its own research on topics that are closely linked to its assessment tasks.