CE. coli isolates in phylogenetic groups B2 and D are more likely to be associated with disease than phylogenetic groups A and B1.
D20 eggs were inoculated for each isolate. There were no deaths in the control groups (PBS-inoculated and uninoculated eggs).
EPathogenicity group of the 2 APEC strains were determined according to a previously described scheme . Highly pathogenic (high) isolates caused mortality or severe lesions (pericarditis, perihepatitis, and/or liver necrosis) in >50% of the chickens inoculated. Intermediate pathogens did not cause death and produced lesions in <50% of chickens inoculated. Weak pathogens (low) produced no mortality and occasional airsacculitis NA – not applicable, because pathogenicity of UPEC isolates for day-old chickens was not determined.