title: Fluctuations in the occurrence of Escherichia coli O157:H7 on a Norwegian farm*.
abstract: OBJECTIVE
  To describe the distribution of Escherichia coli O157:H7 on a sporadically positive dairy farm and on possible contact farms over a one-year period.
  
  
  RESULTS
  Environmental and faecal samples from all animals at the farm, and faecal samples from animals at contact farms were analysed for E. coli O157:H7 by immunomagnetic separation methods or VIDAS. Confirmed isolates were tested for cytotoxicity in the Vero cell assay and typed by PFGE. Escherichia coli O157:H7 (stx2 and eae) of the same PFGE type were isolated from cattle, sheep, hens and environmental samples at variable levels during summer and fall 2002, but were not detected in 2003.
  
  
  CONCLUSIONS
  Escherichia coli O157:H7 had a widespread distribution on the farm investigated, but the original source of contamination could not be identified. The occurrence of this bacterium on the farm did not result in any detectable increase in gastrointestinal disease in the associated population.
  
  
  CONCLUSIONS
  Despite a low endemic level of E. coli O157:H7 in the Norwegian cattle population, the growth and spread of this potentially important bacterium may occur.
authors.affiliation: Norwegian School of Veterinary Science, Oslo, Norway. yngvild.wasteson@veths.no
authors.forename: Y
authors.initials: Y
authors.lastname: Wasteson
authors.forename: G S
authors.initials: GS
authors.lastname: Johannessen
authors.forename: T
authors.initials: T
authors.lastname: Bruheim
authors.forename: A M
authors.initials: AM
authors.lastname: Urdahl
authors.forename: K
authors.initials: K
authors.lastname: O'Sullivan
authors.forename: L M
authors.initials: LM
authors.lastname: Rørvik
mesh_terms: D000383:Agriculture; D000818:Animals; D000829:Animals, Domestic / Q000382:microbiology*; D002417:Cattle; D002645:Chickens; D004285:Dogs; D016521:Electrophoresis, Gel, Pulsed-Field; D004783:Environmental Microbiology; D004927:Escherichia coli Infections / Q000517:prevention & control*; D019453:Escherichia coli O157 / Q000235:genetics / Q000302:isolation & purification*; D005243:Feces / Q000382:microbiology; D006736:Horses; D008372:Manure / Q000382:microbiology; D009664:Norway; D012756:Sheep
chemical_list: D008372:Manure