Indole positive variant of Shigella boydii 1

In a home for mentally handicapped children indole positive variants of Shigella boydii 1 were isolated beside indole negative strains of the same serotype. The variants differed from the indole negative counterparts in fermenting dulcitol, raffinose, and in the absence of splitting trehalose. In antigenic structure the indole positive variant was identical with the type strain. The isolates gave positive guinea pig eye test.