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04:25
Capsular Serotyping of Streptococcus pneumoniae Using the Quellung Reaction
Published on: February 24, 2014
In vivo capsular switch in Streptococcus pneumoniae--analysis by whole genome sequencing
Fen Z Hu1, Rory Eutsey, Azad Ahmed
1Center for Genomic Sciences, Allegheny Singer Research Institute, Pittsburgh, Pennsylvania, United States of America.
Plos One
|November 13, 2012
Summary
Two multidrug-resistant Streptococcus pneumoniae strains from the same pandemic lineage showed significant virulence differences. The type 3 capsule was identified as a major virulence factor, though other determinants may also contribute to disease progression.
Area of Science:
- Microbiology
- Genetics
- Infectious Diseases
Background:
- Two multidrug-resistant Streptococcus pneumoniae strains, SV35-T23 (type 23F) and SV36-T3 (type 3), were isolated during a 1996 pneumococcal disease outbreak.
- Both strains belong to the pandemic lineage PMEN1 but exhibited markedly different virulence in mouse models.
Purpose of the Study:
- To investigate genetic differences between these two strains, focusing on whether capsular genes alone account for their disparate virulence.
- To determine the role of the type 3 capsule as a primary virulence factor in Streptococcus pneumoniae.
Main Methods:
- Whole genome sequencing (WGS) was employed to compare the genetic makeup of the two strains.
- Genetic transformation was used to swap capsular regions between strains.
- Virulence was assessed using mouse models of intraperitoneal infection and chinchilla models of middle ear disease.
Main Results:
- WGS revealed over 2500 single nucleotide polymorphisms and differences in 36 genetic determinants, including capsular and bacteriocin genes.
- Genetic transformation confirmed the type 3 capsule as a major virulence factor, with the recombinant strain SV35-T3* exhibiting high virulence.
- Comparison of SV36-T3 and SV35-T3* suggested additional, yet unidentified, determinants in SV36-T3 contribute to middle ear disease progression.
Conclusions:
- The type 3 capsule is a significant virulence determinant in Streptococcus pneumoniae.
- While the type 3 capsule is crucial, other genetic factors likely influence the full spectrum of virulence and disease pathogenesis.
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