Risk analysis to reduce the appearance of antibiotic-resistant microorganisms in drinking water, dust and manure of broiler farms through adjustments of management measures

The treatment with antibiotics during the fattening of broilers has stagnated in Germany over the last years, while the national aim is to further reduce the use of antibiotics in human and veterinary medicine due to the occurrence of antibiotic-resistances in microorganisms. Therefore, the aim of this study was to identify relevant management measures in broiler farms which improve the health status of broilers and could reduce the occurrence of antibiotic-resistant, opportunistic pathogens in the broilers' environment. A survey was conducted querying existing management measures based on seven different subsections (general operating data, fattening data, management technical data, housing climate, feeding system, health information, cleaning system). Additionally, samples of water, dust and manure were taken in the last week of an average fattening period, and analysed for the occurrence of Staphylococci, Staphylococcus aureus (S. aureus), methicillin-resistant S. aureus (MRSA) and species with resistance to extended-spectrum beta-lactams. The management measures of the participating farms (n = 14) were heterogeneous, with significant differences comparing conventional and organic operating farms, e.g., the number of animals per flock or the duration of the fattening period (in days). Evaluating the predictors which reduce or increase the risk of antibiotic resistance, by using the Firth's penalized logistic regression, various helpful management adjustments could be identified, like regular monitoring of feed and water, especially when using water from one's own well, following climatic recommendations or retrofitting of a cooling system or preventive measures to reduce the use of antibiotics. In conclusion, it seems possible to improve the health status and reduce the frequency of antibiotic treatments in broiler flocks by adjusting management measures, which should lead to a reduced occurrence of antibiotic-resistant, opportunistic pathogens in the broilers' environment.