Modified CAMP test for biogrouping Vibrio cholerae O1 strains and distinguishing them from strains of V. cholerae non-O1

A modified CAMP test was used to identify 973 Vibrio cholerae isolates by phenotype. Eltor and non-O1 strains were CAMP positive; classical strains were CAMP negative. Sausage-shaped zones of hemolysis of eltor strains were easily distinguished from narrower bands of non-O1 isolates. For O1 isolates, there was 100% agreement between the CAMP test and inhibition by polymyxin B.