Occurrence of potentially human-pathogenic Escherichia coli O103 in Norwegian sheep

The investigation of an outbreak of hemorrhagic uremic syndrome in Norway in 2006 indicated that the outbreak strain Escherichia coli O103:H25 could originate from sheep. A national survey of the Norwegian sheep population was performed, with the aim of identifying and describing a possible reservoir of potentially human-pathogenic E. coli O103, in particular of the H-types H2 and H25. The investigation of fecal samples from run_sheep_run585 sheep flocks resulted in 1222 E. coli O103 isolates that were analyzed for the presence of eae and stx genes, while a subset of 369 isolates was further examined for flagellar antigens (H-typing), stxsubtypes, bfpA and astA, and molecular typing by pulsed-field gel electrophoresis (PFGE).

The total ovine E. coli O103 serogroup was genetically diverse by number of H-types, virulotypes and PFGE banding patterns identified, although a tendency of clustering towards serotypes was seen. The flocks positive for potentially human-pathogenic E. coli O103 were geographically widely distributed and no association could be found to county or geographical region.

The survey showed that eae- stx- E. coli O103, probably non-pathogenic to humans, is very common in sheep with 27.5% positive flocks. Moreover, the study documented a low prevalence (0.7%) of potentially human-pathogenic Shiga toxin-producing E. coli O103:H2, while STEC O103:H25 was not detected. However, 3.1% and 5.8% of the flocks were positive for Enteropathogenic E. coliO103 belonging to H-type H2 and H25, respectively. These are of concern as potentially human pathogens by themselves, but more important as possible precursors for human-pathogenic STEC.

Camilla Sekse, Marianne Sunde, Petter Hopp, Torkjel Bruheim, Kofitsyo Sewornu Cudjoe, Bjorg Kvitle, Anne Margrete Urdahl

Applied and Environmental Microbiology. 27 September 2013