Pathogenicity of five rough mutants of Escherichia coli isolated from broilers.
The cultural and pathogenic properties of five rough mutants of avian E. coli were compared with those of four smooth strains. None of the smooth strains showed the ability to agglutinate in aqueous solutions of acriflavine higher than 1:500. On this basis they could be differentiated from the rough strains. In contrast to the smooth strains none of the rough strains grew on D1.5 medium containing 400 microg/ml of crystal violet as an inhibitor. Endotoxin potency was investigated by inoculating 10-day-old chick embryos with bacteria which were dried with alcohol, acetone and ether under vacuum in the presence of CaCl2. Pathogenicity of live bacteria was tested by inoculation of 1-day-old commercial broiler chicks via their yolk sacs. The virulence of two live rough mutants (R1 and R2) in a concentration of 10(4) colony forming units (CFU)/ml of inoculum proved to be higher than that of the smooth strains. Live bacteria of both smooth and rough E. coli under experimental conditions produced the same gross pathology in day-old chicks.
Kloryga
M A
MA
Section of Poultry Diseases, Veterinary Research Institute, Onderstepoort, Republic of South Africa.