Serological studies in cholera. I. Vibrio agglutinin response of cholera patients determined by a microtechnique.

An agglutinin test for the determination of antibody responses to Vibrio cholerae, requiring only 0.025 ml of serum, has been developed. This microtechnique permits the determination of agglutinin titres using fingertip blood, with results comparable with those obtained using venous blood taken at the same time.Among 364 serum pairs in bacteriologically confirmed cases of cholera from an endemic area of East Pakistan, the second serum sample being obtained 6 days or more after the onset of symptoms, a fourfold rise in agglutinin titre occurred in 77.6% of children under 5 years and in 93.2% of persons 5 years of age or older. This titre rise was quite often demonstrated only against a bacterial suspension of the same serotype as the infecting organism. Among 198 serum pairs in bacteriologically negative cases, a fourfold titre rise against the Inaba suspension only was found in 1 case; 5 other persons with fourfold titre rises proved to be household contacts of cholera patients and are taken to represent bacteriological failures or responses to cholera vaccine rather than false positive serological responses.