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Updated: Jun 19, 2026

Capsular Serotyping of Streptococcus pneumoniae Using the Quellung Reaction
Published on: February 24, 2014
THE INTERCONVERTIBILITY OF "R" AND "S" FORMS OF PNEUMOCOCCUS
1Hospital of The Rockefeller Institute for Medical Research.
Abstract:
1. Single cell cultures of "R" pneumococci may revert in all respects to the "S" type. 2. In all instances in which reversion has occurred the "R" forms have invariably reverted to the same specific type from which they were originally derived. 3. The transformation "R" to "S" may be effected in vitro by growth in anti-"R" sera, as well as in vivo by the method of animal passage. 4. Reversion from "R" to "S" whether effected in vivo or in vitro, is always accompanied by the acquisition of maximal virulence.
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