Antitoxin responses to infections with enterotoxigenic Escherichia coli.

Titers of antitoxin to the enterotoxins of Escherichia coli and Vibrio cholerae were determined in acute and convalescent sera from 23 patients with acute choleralike diarrhea in Calcutta, India; the adult rabbit ileal loop model was used for the titration of antitoxin. Six of eight patients harboring enterotoxigenic E. coli, and four of 10 patients who were bacteriologically negative, developed fourfold or greater rises in titer of antibody to E. coli enterotoxin. Five of six patients with cholera also showed significant rises in antitoxin titer against the E. coli enterotoxin, suggesting extensive immunologic cross-reactions between these two enterotoxins. These studies suggest that antibodies to enterotoxin are regularly formed after infection with enterotoxigenic E. coli, and that antitoxin assays might be useful in making retrospective diagnoses of disease caused by these organisms, particularly in an area where cholera is not endemic.