[Demonstration of enteropathogenic E. coli isolated from calves by a test with juvenile mice]. / Dokazvane na enteropatogenni E. coli, izolirani ot teleta chrez testa s infantilni mishki.

ABSTRACT

The test with infantile mice was used to determine the enteropathogenicity of 272 Escherichia coli strains isolated from coli-bacteriosis-affected and dead calves. Forty-three (15.8 per cent) of the strains were found to be enteropathogenic. The results were confirmed through the study of the strains with the use of ligated intestinal segments. The results obtained with the two methods were positively correlated. The test with infantile mice was rapid and readily applicable in the routinely used technique for the demonstration of enteropathogenic E. coli organisms producing a thermostable enterotoxin. It was also established that heating at 80 degrees C for 30 min did not destroy the enterotoxic activity in 33.3 per cent of the strains. The full elimination of the enterotoxic activity produced by E. coli could be achieved through autoclaving at 120 degrees C for 30 minutes. The results from the heat experiments made it reasonable to believe that the thermostable enterotoxin, produced by bovid E. coli organisms, presents molecular heterogeneity.