Pathogenicity of Escherichia coli in aerosols for young chickens

The relative pathogenicity of Esherichia coli isolates from poultry was determined by aerosol exposure of young chickens. Evidence of colisepticemia with airsacculitis and/or pericarditis and perihepatitis was evaluated. A system was devised that included the intratracheal (IT) inoculation of strain SE-17 infectious bronchitis virus (IBV) of chicks at 7 days of age followed by their aerosol exposure to E. coli culture suspensions 2 days later. Each experiment was terminated 6 days later. For comparative purposes in some studies, chicks were housed at 17 C and others at 27 C. The IBV-E. coli challenge procedure proved to be an effective way to determine the relative ability of E. coli isolates to cause death and/or gross lesions in young chickens. With some E. coli isolates, there were minimal or no obvious adverse effects from exposure except when chickens were previously inoculated with IBV. When chicks were housed at 17 C instead of 27 C, slight increases in mortality and decreases in gross lesions were generally observed, probably because the earlier deaths did not allow time for the lesions to become as evident. The E. coli isolate #18344 (Congo Red-positive) was consistently more pathogenic than the Congo Red-negative version of that isolate. Cultures of E. coli previously demonstrated to be pathogenic (VA O1:K1 and DL #29) were among the most pathogenic isolates evaluated in these experiments and were similar to the Congo Red-positive #18344 isolate.(ABSTRACT TRUNCATED AT 250 WORDS)