CHARACTERIZATION OF ESCHERICHIA-COLI ISOLATED FROM THE TONSILS OF CATTLE

During our studies on tonsillar colonization by Pasteurella haemolytic a, we consistently found Escherichia coli to be one of the most promin ent and prevalent bacterial species in the tonsils of healthy cattle. Since tonsillar isolates have not been characterized, we grouped 124 i solates from 87 healthy cattle from eight sources by hemolytic zone si ze and by carbon source utilization and probed them for selected virul ence genes. They formed 3 groups by hemolytic zone size and 18 groups (of 2 to 31 isolates) by their metabolic patterns. Most groups include d isolates from more than one source. Two isolates contained the Shiga -like toxin gene, and nine others contained the F41 accessory gene.