The Demonstration of Phase Variation in Salmonella abortus-equi

Abstract

Study of the supposedly monophasic S. abortus-equi by the Wassen technique revealed that this organism contained 3 phases. Phase 1 is identical with the flocculating antigens of S. paratyphi A. Phase 2 is the form in which the species naturally occurs. Phase 3 is related to, but not identical with, the [beta] phase of the Schleissheim type. The phases are reversible and by use of suitable serums, one phase may be changed to either of the others. This is the first instance in which more than 2 phases have been demonstrated in a Salmonella. It is also the first instance in which induced phases isolated from monophasic specific types have been proved to be reversible.