Congo red binding and Plasmid Profile of E. coli Isolates of Poultry Origin

The Congo red binding ability is used as a phenotypic marker of colisepticaemic (invasive) and non-coliseptecaemic E. coli in poultry and also as an epidemiological marker for discrimination of pathogenic strains from the commensals.The Congo red binding ability and plasmid profile of 70 E. coli isolates from poultry was studied.A total of 65 (92.86 %) isolates showed a Congo red binding ability while 5 (7.14 %) isolates did not bind Congo red dye up to 72 hours post inoculation (PI).Out of 70 isolates tested, 37 (52.86 %) isolates showed the presence of plasmid, while 33 (47.14 %) isolates did not reveal any plasmid.The molecular mass of the plasmids was found to be more than 50 kb.