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Respiratory Syncytial Virus Disease01:29

Respiratory Syncytial Virus Disease

Human respiratory syncytial virus (RSV) is a widespread pathogen that primarily targets infants and young children but also poses a serious health risk to elderly and immunocompromised individuals. Belonging to the Pneumoviridae family, RSV is a negative-sense, single-stranded RNA virus within the Pneumovirus genus. Its global health burden is significant, with millions of cases annually resulting in hospitalizations and mortality, particularly in resource-limited settings. Although most...
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Capsular Serotyping of Streptococcus pneumoniae Using the Quellung Reaction
04:25

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Published on: February 24, 2014

THE INTERCONVERTIBILITY OF "R" AND "S" FORMS OF PNEUMOCOCCUS.

M H Dawson1

  • 1Hospital of The Rockefeller Institute for Medical Research.

The Journal of Experimental Medicine
|October 30, 2009
PubMed
Summary
This summary is machine-generated.

Pneumococci R forms can revert to the original S type in vitro or in vivo. This R to S type transformation is linked to regaining full virulence, offering insights into bacterial genetics and pathogenicity.

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Last Updated: Jun 19, 2026

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Area of Science:

  • Microbiology
  • Bacterial Genetics
  • Pathogenesis

Background:

  • Pneumococci exist in distinct R (rough) and S (smooth) forms, differing in colony morphology and virulence.
  • Understanding the mechanisms of bacterial type transformation is crucial for controlling infectious diseases.

Purpose of the Study:

  • To investigate the phenomenon of R-to-S type reversion in pneumococci.
  • To determine the conditions and outcomes associated with this bacterial transformation.

Main Methods:

  • Culturing of single-cell pneumococci R forms.
  • Induction of R-to-S reversion using in vitro methods (growth in anti-R sera) and in vivo methods (animal passage).

Main Results:

  • Pneumococci R forms demonstrated the capacity to revert to their original S type.
  • Reversion was specific, with R forms returning to their original S type.
  • Both in vitro and in vivo methods successfully induced R-to-S transformation.

Conclusions:

  • The R to S type transformation in pneumococci is a reversible process.
  • Acquisition of maximal virulence consistently accompanies R-to-S reversion, highlighting its significance in bacterial pathogenicity.