Occurrence and characterization of Escherichia coli O157 isolated from cattle in Norway

Faecal samples from 504 imported beef cattle were screened to investigate t he occurrence of Escherichia coli O157. The results were compared with thos e from a previous screening of Norwegian dairy cattle, and the occurrence w as found to be higher in the imported beef cattle. The E. coli O157 isolate s from the previous and present studies were characterized for the genes en coding for shigatoxin 1 (stx(1)), shigatoxin 2 (stx(2)), the intimin protei n (eae) and the flagellar protein H7 (fliC) using PCR analysis, pulsed-fiel d gel electrophoresis (PFGE) with the restriction enzyme XbaI, and bacterio phage lambda RFLP analysis using the PvuII restriction enzyme. The isolates from the dairy and beef cattle could be distinguished by the profiles of t he toxin genes and by PFGE patterns. Whether the importation of animals in itself should be regarded as a risk factor for the occurrence of E. coil O1 57, or whether other management factors contribute to the differences in ca rrier rates compared to the previous study on domestic cattle, is discussed .