512 The challenge of Antimicrobial resistance on the animal-human-environment interface.

Antibiotic resistant microorganisms represent a challenge for livestock farming worldwide. In addition to the sometimes dramatic reduction of therapeutic options for treatment of diseased animals, the possible transmission of these pathogens to humans via animal food products is also a very important issue. While in the past there were usually specific, resistant pathogens, today there is increasing focus on commensal, resistant microorganisms, since these primarily harmless bacteria can transfer their resistance genes to pathogenic pathogens under antibiotic therapy. Currently, MRSA in pigs, ESBL-producing E. coli and MCR1-positive E. coli in pigs and poultry, as well as increasingly also carbapenem-resistant E. coli, are of special interest. The causes and ways for the emergence and spread of these resistant pathogens are different. Common to all these resistant pathogens is that they are often transmitted across different stages of production. In addition, only a few pathogens are usually required for a colonization of susceptible animals and a selection pressure by antibiotic treatment is not mandatory. In addition, factors for higher environmental tenacity and colonization ability also appear to be encoded on the resistance plasmids of the resistant bacteria, e.g. at ESBL-E. coli. The entry of these pathogens into the farms takes place via newly staked animals or through contaminated feed, infected rodents and flies or colonized employees. Once in the stable, these pathogens can persist for very long time and even intensive disinfection measures are often unsuccessful, since even very low numbers of pathogens can lead to a new infection. In addition, some disinfectants can also cause resistance themselves, including co-resistance to antibiotics. Finally, resistant microorganisms are emitted from the stables into the environment with the exhaust air and with litter and manure. There they pose a risk to wildlife, to local residents or for re-entrance into neighboring farms.