Use of antibiotics in agriculture decreasing, antibiotics resistance stagnating
On the occasion of the international symposium "Antimicrobial Resistance in the Food Chain" organised by the German Federal Institute for Risk Assessment (BfR) and held on 2 and 3 November 2015, over 200 experts will discuss how antimicrobial resistance can be reduced in veterinary and human medicine. "One positive insight from our studies is that antibiotic-resistant germs are no longer on the increase in the food chain. This means that the negative trend of the last years has stopped", says BfR President Professor Dr. Dr. Andreas Hensel. "It is now important to establish the causes for this first positive finding and to take further measures." Professor Hensel explained that one possible reason for the lower number of antibiotic-resistant germs in foods is that the use of antimicrobials in agriculture is declining. At the symposium, the international experts from the disciplines of livestock breeding, veterinary medicine and human medicine will, among other questions, discuss to what extent the measures already taken to reduce antimicrobial resistance are sufficient or whether they may have to be extended or modified. The relevance of the topic for users is also shown by the current 2015 consumer monitor, a representative survey conducted by the BfR. According to this survey, seven out of ten participating consumers are worried about antibiotic-resistant germs contained in foods.
The quantity of antimicrobial veterinary medicine dispensed to veterinarians decreased from about 1706 tons (t) in the year 2011, the first year of the survey, to about 1238 t in 2014. This development accords with the first results from the BfR research project VetCAb Sentinel (Veterinary Consumption of Antibiotics) undertaken by the University of Veterinary Medicine Hannover. The number of antimicrobial treatments in fattening pigs fell from about five days per livestock place and half-year in 2011 to about one day per livestock place and half-year in 2014. The data show that there has been a change in the prescription behaviour of German livestock veterinarians. What factors led to this change will be the subject of investigations in the coming years. One year ago, the German Pharmaceuticals Act was changed and it became mandatory for livestock farmers to report, above a certain stock size, the use of antimicrobials in their animal population. Livestock facilities that use more drugs than comparable facilities must take measures to reduce their use of medication.
The main focus of the current resistance debate is on ESBL/AmpC-forming germs, since they pose a special problem in human medicine. ESBL (extended-spectrum beta-lactamases) und AmpC denote enzymes which render ineffective a broad spectrum of antibiotics including Cephalosporins of the third generation, meaning that the germs are resistant to these antibiotics. As part of the National Resistance Monitoring conducted by the BfR in 2014, no further rise, following years of expansion, was found in the resistance rates to Cephalosporins in E.coli germs. The proportion of ESBL and / or AmpC-forming germs in E.coli isolates from the broiler meat chain fell from 6.7 % in the year 2013 to 3.7 % in 2014, and in the turkey meat chain from 3.2 % to 2.6 %.
Another result of the National Resistance Monitoring shows that in the testing procedure introduced in 2014 not a single isolate was found where a carbapenemase was present. Carbapenemases are enzymes which lead to resistance of bacteria to carbapenemes. Carbapenemes are antimicrobials of special significance in the treatment of humans. They must be used only where other antibiotics are no longer effective.
The resistance rates to fluoroquinolones, a further class of antibiotics especially important for therapeutic purposes have been stable at the same high level for years. In the broiler meat chain, the rate fell from 48.8 % (2013) to 46.3 % (2014), whereas in the turkey meat chain, the rate increased from 37.4 % (2012) to 40.6 % (2014). This means that there was no consistent trend.
Results from the resistance monitoring as well as scientific studies conducted as part of the research association RESET (Resistance in humans and animals) indicate that in broiler breeding the transmission of germs via the parent animals is an important source of infection of breeding stocks with ESBL/AmpC-forming germs. Current research by the Institute for Animal Hygiene at the Free University of Berlin also shows, however, that more and more ESBL/AmpC-negative day-old chicks enter production populations, suggesting that this route of contamination is becoming less important. The germs are now introduced from the environment during fattening.
A comparison of resistance patterns in the food chain indicates that pathogens which can be detected in the stable are spread along the food chain and can enter private households via contaminated meat. Experimental studies show that during meat processing, high numbers of germs can be transferred from the meat to kitchen utensils. The introduction of resistant pathogens to private households via raw meat due to a lack of kitchen hygiene can mean that consumers ingest resistant germs.
Comparisons of the spread of resistant genes and other pathogenic properties show that ESBL-forming bacteria from production animals and foods can lead to infections in human medicine. However, it is not possible to quantify as yet to what extent humans are populated with germs from livestock farming. Current results demonstrate that apart from the various production animals, domestic animals too can lead to humans being colonised by antibiotic-resistant bacteria.
Bacteria need a certain “resistance gene” in order to produce the enzymes ESBL and AmpC. The use of antimicrobials in humans and animals facilitates the spread of ESBL and / or AmpC-forming bacteria, because resistance to antibiotics constitutes an advantage in the competition against other (types of) bacteria.
About the BfR
The German Federal Institute for Risk Assessment (BfR) is a scientific institution within the portfolio of the Federal Ministry of Food and Agriculture (BMEL) in Germany. 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.