M NÜESCH-INDERBINEN¹, A MÜLLER¹, R STEPHAN<sup>1

1</sup>Institute for Food Safety and Hygiene, University of Zurich, Winterthurerstr. 272, 8057 Zurich, Switzerland

In this study, extended-spectrum ß-lactamase (ESBL)-producing E. coli isolates recovered from the following sources were characterized with regard to the occurrence and distribution of uropathogenic and enteric pathogenic virulence factors: surface waters (rivers and lakes), the intestines of freshwater fish, fresh vegetables, retail poultry meat and the fecal samples of livestock, healthy humans and primary care patients. Among the 207 isolates, 82% tested positive by PCR for one or more of the virulence factors (VF) that predict uropathogenicity, TraT, fyuA, chuA, PAI, yfcv or vat. Uropathogenic Escherichia coli (UPEC) was detected in each of the analyzed sources. Regarding virulence factors for intestinal pathogenic E. coli, these were found to be rarer and predominantly associated with the aquatic environment, with aagR (EAEC) found in isolates from surface waters and STp and LT associated with isolates from fish. Aggregate VF scores were lowest among isolates belonging to phylogenetic group B1 and highest among group B2. Clustering of the isolates by phylogenetic group, multilocus sequence type (MLST) and ESBL-types detected clonal overlaps of A:ST10(CTX-M-1) and D:ST350(CTX-M-1) between the sources of livestock, poultry meat and healthy humans, suggesting animal food, in particular poultry, represents a potential reservoir for these particular UPEC clones. The clones A:ST10(CTX-M-55) and B2:ST131(CTX-M-27), harbouring uropathogenic virulence factors were significantly associated with fresh vegetables and with fish, respectively. Further clonal complexes with source overlaps included D:ST38(CTX-M-14), D:ST69(CTX-M-15), D:ST405(CTX-M-15) and D:ST648(CTX-M-15), which were found in surface water and healthy humans. Identifying potential reservoirs of UPEC in the environment, animals, food and humans is important in order to assess routes of transmission and risk factors for acquiring UPEC.