Prevalence and molecular characterization of Escherichia coli O157:H7 by multiple-locus variable-number tandem repeat analysis and pulsed-field gel electrophoresis in three sheep farming operations in California.

A year-long study was conducted to determine the fecal prevalence of Escherichia coli O157:H7 in three sheep ranches. Strain diversity and persistence were compared with multiple-locus variable-number tandem repeat analysis and pulsed-field gel electrophoresis. Ranch C, a feedlot, consisted of young sheep raised predominantly on a high-grain diet.