Source attribution of foodborne ESBL-E. coli in Germany

Extended-spectrum beta-lactamases (ESBL) confer resistance over a wide spectrum of ß-lactam antibiotics, including penicillins, 2nd-, 3rd- and 4th-generation cephalosporins. Furthermore, such bacteria are often resistant to other antimicrobial classes by associated resistance mechanisms. This can be challenging if human infections have to be treated. Also problematic is the fact that these resistance genes are often located on mobile elements which can be spread intra- and inter-species. These days, there is an intensive discussion about the origin of ESBL-producing E. coli in humans. We estimated the contribution of different animal sources (broiler, fattening pigs, dairy cattle, fattened cattle) to human cases, using data from several ongoing studies within the German RESET project [1]. Our model, derived from the well established Salmonella source attribution model based on microbial subtyping data [2] uses information on typing of E.coli, isolated by selective media from humans and different animal reservoirs, by their ESBL-genes, phylogenetic groups and prevalence rates. First attempts using preliminary data sets indicated that many human cases can not be explained by the animal sources considered. Furthermore, it showed that typing information considered to define the subtypes was not sufficient discriminatory to differentiate the contribution of the individual sources. The results indicate, that all sources considered may contribute to the exposure of humans. We will present model results from an updated German dataset for ESBL-producing E. coli including antimicrobial resistance patterns. This approach can help to assess the role of foodborne exposure.