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Implementation of a Permeable Membrane Insert-based Infection System to Study the Effects of Secreted Bacterial Toxins on Mammalian Host Cells
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Complementation of a speA negative Streptococcus pyogenes with speA: effects on virulence and production of

M Unnikrishnan1, J Cohen, S Sriskandan

  • 1Department of Infectious Diseases, Imperial College School of Medicine, Hammersmith Hospital, Du Can Road, London W12 0NN, UK.

Microbial Pathogenesis
|August 14, 2001
PubMed

Insights

Streptococcus pyogenes strains lacking streptococcal pyrogenic exotoxin A (SPEA) did not show reduced virulence. This study confirms SPEA is not crucial for invasive infections in mice.

Area of Science:

  • Microbiology
  • Infectious Diseases
  • Toxicology

Background:

  • Streptococcus pyogenes virulence is complex.
  • Previous studies suggested SPEA might be important for invasive disease.

Purpose of the Study:

  • To investigate the role of streptococcal pyrogenic exotoxin A (SPEA) in invasive Streptococcus pyogenes infections.
  • To determine if SPEA is essential for bacterial invasiveness in a murine model.

Main Methods:

  • Created a complemented strain (H361) with increased SPEA production compared to wild-type (H305).
  • Inoculated mice with SPEA-negative, wild-type, and complemented strains.
  • Quantified bacterial counts and SPEA levels in infected murine tissues.

Main Results:

  • Complementation with speA in strain H361 led to reduced virulence and bacterial load in vivo.
  • Despite higher in vitro production, strain H361 did not produce more SPEA than the wild-type in infected mouse tissues.
  • SPEA production levels in vivo did not correlate with virulence.

Conclusions:

  • Streptococcal pyrogenic exotoxin A (SPEA) does not appear to play a key role in the invasiveness of Streptococcus pyogenes in this murine model.
  • Virulence in invasive streptococcal infections is likely mediated by factors other than SPEA.

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