Escherichia coli Hemagglutinin Response of Adult Volunteers to Ingested E. coli 055 B5

Summary The E. coli hemagglutinin response of adult volunteers to ingestion of E. coli 055 and a “normal” strain of E. coli, respectively, was determined. 1. Increase in E. coli 055 hemagglutinin titers was observed in all subjects following administration of living organisms in large numbers and in two-thirds of individuals who received smaller numbers. 2. None of the controls who received milk without E. coli showed such an antibody response, nor did the volunteers who ingested large numbers of killed 055 organisms or viable bacteria of a “normal” strain of E. coli. 3. Good correlation was found between increases of E. coli 055 hemagglutinin titers and the appearance of bacterial O agglutinins. 4. The E. coli hemagglutination test proved to be more sensitive than the conventional bacterial agglutination test, inasmuch as the former method with the postfeeding serum specimens yielded antibody titers which were from 5 to 20 times higher and detected antibodies in prefeeding serum specimens which were not demonstrated by the latter method.