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09:11
Capsular Serotyping of Streptococcus pneumoniae by Latex Agglutination
Published on: September 25, 2014
Streptococcus pneumoniae resistance to complement-mediated immunity is dependent on the capsular serotype.
Catherine Hyams1, Jose Yuste, Katie Bax
1Centre for Respiratory Research, Department of Medicine, University College Medical School, Rayne Institute, 5 University Street, London WC1E 6JJ, United Kingdom.
Infection and Immunity
|December 2, 2009
Summary
Capsular serotype influences Streptococcus pneumoniae virulence by affecting complement immunity. Specific serotypes like 6A and 23F show reduced complement resistance, leading to lower virulence in mouse models.
Area of Science:
- Microbiology
- Immunology
- Infectious Diseases
Background:
- Streptococcus pneumoniae strains exhibit variable virulence, partly due to capsular serotype.
- The bacterial capsule impedes host immunity, but strain-specific genetic differences complicate serotype effect assessment.
Purpose of the Study:
- To investigate the direct impact of capsular serotype on Streptococcus pneumoniae interactions with the complement system.
- To determine if serotype-specific effects on complement immunity correlate with bacterial virulence.
Main Methods:
- Utilized capsular serotype-switched TIGR4 mutant strains of Streptococcus pneumoniae.
- Employed flow cytometry to quantify C3b/iC3b deposition on bacterial strains.
- Assessed neutrophil phagocytosis in the presence of complement.
- Evaluated bacterial virulence in a mouse model of sepsis.
Main Results:
- Significant differences in C3b/iC3b deposition were observed among serotypes, independent of capsule thickness.
- Serotypes 6A and 23F showed increased C3b/iC3b deposition compared to 7F and 4, even without antibodies.
- Increased C3b/iC3b deposition correlated with enhanced neutrophil phagocytosis and reduced virulence in vivo.
Conclusions:
- Capsular serotype directly influences resistance to complement-mediated immunity in Streptococcus pneumoniae.
- Serotype-specific variations in complement evasion contribute to differences in bacterial virulence and invasiveness.
- These findings highlight a mechanism by which capsular serotype modulates host-pathogen interactions.
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