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The group A Streptococcus pathogenicity island RD2: virulence role and barriers to conjugative transfer

Roshika Roshika1, Sushila Baral1, Ira Jain1

  • 1Department of Microbiology & Immunology, Reno School of Medicine, University of Nevada, Reno, Nevada, USA.

Infection and Immunity
|November 27, 2024
PubMed

Insights

Serotype M28 group A Streptococcus (GAS) isolates are linked to puerperal sepsis. A pathogenicity island, RD2, is restricted due to a Type I restriction-modification system, not capsule presence.

Area of Science:

  • Microbiology
  • Genetics
  • Infectious Diseases

Background:

  • Serotype M28 group A Streptococcus (GAS) isolates show a strong association with puerperal sepsis.
  • The RD2 pathogenicity island is present in M28 GAS but largely absent in other serotypes, suggesting its role in this association.

Purpose of the Study:

  • To investigate the factors restricting the spread of the RD2 pathogenicity island between different GAS serotypes.
  • To understand how RD2 influences GAS virulence and its association with puerperal sepsis.

Main Methods:

  • Conjugation assays were performed to assess RD2 transfer frequency between GAS serotypes.
  • The role of the hyaluronic acid capsule in RD2 acquisition and GAS virulence was evaluated.
  • A Type I restriction-modification system was identified as a key factor in inter-serotype transfer restriction.
  • Transcriptomic analysis was used to study RD2's effect on GAS gene expression.

Main Results:

  • RD2 conjugation frequency was significantly reduced in inter-serotype assays compared to intra-serotype assays.
  • The hyaluronic acid capsule did not affect RD2 conjugation frequency or vaginal colonization but inhibited adherence.
  • A conserved, chromosomally encoded Type I restriction-modification system was identified as the primary barrier to RD2 transfer.
  • RD2 was found to alter the GAS transcriptome, affecting virulence factors involved in adherence and dissemination upon exposure to human plasma.

Conclusions:

  • The Type I restriction-modification system is a crucial factor limiting the spread of the RD2 pathogenicity island to specific GAS serotypes.
  • Understanding these genetic barriers provides insights into the population structure of GAS and the evolution of virulence.
  • The findings contribute to understanding the specific association of M28 GAS with puerperal sepsis.
Keywords:
Streptococcus pyogenesconjugationmolecular geneticspathogenesispathogenicity islandsvirulence

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