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Acquisition of the Sda1-encoding bacteriophage does not enhance virulence of the serotype M1 Streptococcus pyogenes

Carola Venturini1, Cheryl-Lynn Y Ong, Christine M Gillen

  • 1School of Chemistry and Molecular Bioscience and Australian Infectious Diseases Research Centre, The University of Queensland, St. Lucia, QLD, Australia.

Infection and Immunity
|March 27, 2013
PubMed

Insights

The highly virulent Streptococcus pyogenes M1T1 clone

Area of Science:

  • Microbiology
  • Genetics
  • Infectious Diseases

Background:

  • The invasive Streptococcus pyogenes (group A Streptococcus [GAS]) M1T1 clone has emerged globally.
  • This clone acquired bacteriophages encoding DNase Sda1 and superantigen SpeA, enhancing virulence.

Purpose of the Study:

  • To investigate the role of the Sda1-encoding phage in GAS virulence.
  • To determine if horizontal gene transfer of Sda1 alone confers hypervirulence.

Main Methods:

  • Lysogenic conversion used to transfer Sda1-encoding phage from M1T1 strain 5448 to M1 strain SF370.
  • Assessed virulence factors including neutrophil evasion, covRS mutation, and lethality in a humanized mouse model.

Main Results:

  • Sda1 was expressed in the phage-converted SF370 strain.
  • No enhanced neutrophil survival, hyperinvasive covRS mutant formation, or increased lethality was observed.

Conclusions:

  • The Sda1-encoding phage alone does not confer hypervirulence to the M1T1 clone.
  • Hypervirulence of the M1T1 clone likely results from Sda1 acting synergistically with the M1T1 genetic background.

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