Abstract
During an epidemiologic study of poultry colisepticemia on 2 Saudi Arabian poultry broiler farms, E. coli was isolated from 101 (40.45) of the 250 specimens examined. The antigenic structure and the drug resistance pattern of 65.4% of the E. coli isolates from different sources were used as epidemiologic markers to trace the source of the infection. E. coli strains with typical epidemiologic markers were isolated from various sources on a broiler breeding farm, but not from well waters of the infected progeny farm.