ABSTRACT
In the present investigation, O8, O2, O41, O154 and O78 serotyping of E. coli were chosen as representative strains to evaluate their pathogenicity using chick inoculation technique. Serotyping of isolated E. coli strains (carried out at the National Salmonella and Escherichia Centre, CRI, Kasuali) showed 28 different typable, 5 untypable and 3 rough sero types. The enteropathogenicity test of five widely distributed isolates of E. coli viz. O8, O2, O41, O154 and O78 serotypes indicates that O2, O154 and O78 strains of E. coli are pathogenic by intraperitoneal and intratracheal route of inoculation in chicks. Out of these, O78 has been found to be highly pathogenic by intraperitoneal as well as intratracheal route of inoculation.

Key Words: Chicks. Pathogenicity, E coli serotypes, Intraperitoneal, Intratracheal