ETIOLOGIC DIAGNOSIS OF DIARRHEAL DISEASES OF CALVES - FREQUENCY AND METHODS FOR DETECTING ENTEROTOXIN AND K99 ANTIGEN PRODUCTION BY ESCHERICHIA-COLI

Abstract

E. coli isolated from calves in Minnesota and Montana [USA] were tested for enterotoxigenicity via bioassay of cell-free broth culture fluid and for K99 antigen via a serum agglutination test. Infant mice were used to assay for heat-stable enterotoxin (ST), and [y-1 mouse] adrenal [tumor] cells in culture were used to assay for heat-labile enterotoxin (LT). Of the 345 E. coli isolates, 46 produced ST enterotoxin; none produced LT enterotoxin. Of the 46 enterotoxigenic isolates, 35 had K99 antigen; only 9 of 66 nonenterotoxigenic isolates so tested had this antigen. The enterotoxigenicity of 28 additional E. coli isolates known or suspected to be calf enteropathogens and provided by 3 different laboratories was also tested. All isolates from 2 laboratories produced ST but not LT. All isolates from the 3rd laboratory produced LT but not ST. E. coli organisms that were positive in the infant mouse assay also caused positive ligated, jejunal-loop responses in calves and in 9 day old (but not 5 wk old) pigs. The infant mouse and adrenal cell tests for ST and LT, combined with the agglutination test for K99, would be useful in the diagnosis of enteric enterotoxic colibacillosis of calves.