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Fatal S. aureus hemorrhagic pneumonia: genetic analysis of a unique clinical isolate producing both PVL and TSST-1

Zhi Li1, Dennis L Stevens, Stephanie M Hamilton

  • 1Veterans Affairs Medical Center, Boise, Idaho, United States of America. lizhi_lily@hotmail.com

Plos One
|November 24, 2011
PubMed

Insights

A rare Staphylococcus aureus strain producing Panton-Valentine leukocidin (PVL) and toxic shock syndrome toxin-1 (TSST-1) was identified. These toxin genes are carried on a novel phage and pathogenicity island, raising concerns about emerging hypervirulent strains.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Genetics

Background:

  • Staphylococcus aureus can cause severe infections.
  • Co-production of Panton-Valentine leukocidin (PVL) and toxic shock syndrome toxin-1 (TSST-1) by S. aureus is uncommon.
  • A fatal case of necrotizing pneumonia was linked to an unusual MSSA strain.

Purpose of the Study:

  • To investigate the molecular organization of PVL and TSST-1 genes in the identified MSSA strain (MSSA68111).
  • To understand the genetic elements responsible for co-production of these toxins.
  • To assess the potential for emergence of hypervirulent S. aureus strains.

Main Methods:

  • Molecular characterization of toxin gene organization.
  • Phylogenetic analysis of phage and staphylococcal pathogenicity island (SaPI).
  • Assessment of transmissibility of genetic elements.

Main Results:

  • The PVL genes were located on a novel temperate prophage, ФPVLv68111, similar to the rare ФPVL phage.
  • The TSST-1 gene was found on a unique SaPI, SaPI68111, likely resulting from recombination.
  • Both genetic elements, ФPVLv68111 and SaPI68111, are mobilizable and transmissible.

Conclusions:

  • The co-production of PVL and TSST-1 in MSSA68111 is mediated by distinct, mobilizable genetic elements.
  • These findings highlight the potential for the emergence and global spread of hypervirulent S. aureus strains.
  • Further surveillance is warranted to monitor the dissemination of such toxin-encoding mobile genetic elements.

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