EN
Two hundred and twenty E. coli strains isolated from cases of poultry colibacillosis in Poland were studied serologically. One hundred and ninety-six (89 per cent) were identified as belonging to 37 different O groups. Ninety-three strains (42 per cent) belonged to 6 serotypes considered to be pathogenic for poultry. The seriotypes were: O1:K1, O2:K1, O3:K?, O8:K?, O22:K?, O78:K80. The greatest number of strains were represented by serotypes O2:K1 and O8:K. In the studied strains serogroups considered to be pathogenic for cattle and humans were found. Out of the remaining strains, O90:K? Was encountered most frequently, followed by O93:K? and O84:K?. These serotypes had so far not been considered to be pathogenic for poultry.