Abstract
For a decade it has been recognized that the amount of type-substance in different cultures of the same serological type of Group
A hemolytic streptococci manifests considerable variation. The limits of this antigenic variability in different strains of the same type, in different culture-phases of the same strain or in different colony cultures of the same strain and phase have, however, never been clearly related to the chief dissociative variants, with the exception of the early reports of Todd and Lancefield 1 and of Lancefield and Todd 2 on smooth and matt forms, and the later observations of Griffith. 3
Observations on dissociative behavior had suggested to us that, among the variability-phenomena often associated with the R to S “reversion”, there might arise smooth strains in which the type- or group-factor had been largely lost. A detailed study of cultures of hemolytic streptococci undergoing the R to S transformation has shown marked quantitative differences relating to type- and group-substances in different smooth-colony lines derived from the rough form. Study of these type- and group-cultures was of special interest because they represented antigenic variants within a single culture-phase.
From a smooth Type 5 strain a stable rough form was produced by encouraging the development of rough, marginal “outbursts” on typical smooth colonies. Upon reversion of this rough to smooth, following rapid broth-passages, 2 smooth colonies, macroscopically identical and containing organisms of similar morphological, cultural, and biochemical characters, were selected for further investigation. One colony-culture, 10-1S, gave maximal reactions, by the slide-agglutination technic of Griffith, 3 in Group A serums but no reaction in Type 5 serums from which the group-antibodies had been removed by absorption with a heterologous-type strain. The other colony-culture, 10-2S, gave maximal reactions in Type 5 serums but no reaction in Group A serums. It thus appeared that the former culture was heavily endowed with group-substance while the latter appeared to be equally endowed with type-substance.
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