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Distribution and regulation of the mobile genetic element-encoded phenol-soluble modulin PSM-mec in

Som S Chatterjee1, Liang Chen, Hwang-Soo Joo

  • 1Laboratory of Human Bacterial Pathogenesis, National Institute of Allergy and Infectious Diseases, The National Institutes of Health, Bethesda, Maryland, United States of America.

Plos One
|December 17, 2011
PubMed

Insights

The phenol-soluble modulin PSM-mec toxin is frequently found in methicillin-resistant Staphylococcus aureus (MRSA). Its expression is controlled by AgrA, and it has a minor impact on MRSA virulence.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Genetics

Background:

  • Phenol-soluble modulin PSM-mec is a unique staphylococcal toxin encoded on the mobile antibiotic resistance determinant, the staphylococcal cassette chromosome (SCC) element mec.
  • This element confers methicillin resistance in Staphylococcus aureus.

Purpose of the Study:

  • To investigate the distribution, regulation, and virulence role of the PSM-mec peptide and its gene locus in MRSA.
  • To clarify the regulatory mechanisms controlling psm-mec expression and its impact on MRSA pathogenesis.

Main Methods:

  • Analysis of psm-mec gene distribution in MRSA strains of SCCmec types II, III, and VIII.
  • Controlled expression studies in agr mutants to determine regulation by AgrA and RNAIII.
  • Construction and analysis of psm-mec isogenic deletion mutants in a mouse model of skin infection.

Main Results:

  • The psm-mec gene is frequently found in MRSA strains with SCCmec types II, III, and VIII, forming a conserved part of the class A mec gene complex.
  • PSM-mec expression is controlled by AgrA independently of RNAIII and shows high variability.
  • psm-mec deletion mutants exhibited minor changes in PSMα peptide production and virulence compared to wild-type strains.

Conclusions:

  • PSM-mec is a conserved component in specific MRSA SCCmec types, regulated by AgrA.
  • The PSM-mec peptide's direct contribution to MRSA virulence appears minor, with its regulatory RNA impact being limited in the original strain background.

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