A new type of antigenic variation occurring in the Flexner group of dysentery bacilli

Abstract

The Flexner dysentery bacilli are non-flagellated, and their agglutination is determined by somatic antigens situated at the cell surface. So far as the author is aware, phasic variations, of the kind that Andrewes (1922) demonstrated in the flagellar antigens of the bacilli of the typhoid-paratyphoid group, have not yet been observed in the case of 0 antigens; but the variations described above would appear to be of this type. The V, W and Z strains examined gave rise to variants, such as Vb, that had lost, completely or almost completely, the group somatic antigen, or antigens, but showed a consistent tendency to revert to the form in which the group antigens were present.No evidence could be obtained of variants in which the group antigens were present, while the specific antigen was lacking; but the substrains, such as Va, that showed the presence of both group and specific antigens, appeared to differ from the parent strain in showing no tendency to give rise to variants of the Vb type.