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A Fluorescence-based Method to Study Bacterial Gene Regulation in Infected Tissues
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A Fluorescence-based Method to Study Bacterial Gene Regulation in Infected Tissues

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Illness severity in community-onset invasive Staphylococcus aureus infection and the presence of virulence genes

Michael C Wehrhahn1, J Owen Robinson, Elaine M Pascoe

  • 1Department of Microbiology and Infectious Diseases, Royal Perth Hospital and PathWest Laboratory Medicine, WA. mcwehrhahn@hotmail

The Journal of Infectious Diseases
|April 12, 2012
PubMed
Abstract

Insights

Virulence in Staphylococcus aureus infections depends on the entire bacterial genotype, not just specific genes like PVL. Community-onset MRSA and MSSA clones vary in severity, with MSSA clones causing more severe invasive infections.

Area of Science:

  • Microbiology
  • Infectious Diseases
  • Genomics

Background:

  • Invasive community-onset methicillin-resistant and methicillin-sensitive Staphylococcus aureus (cMRSA/cMSSA) infections present a significant public health challenge.
  • The specific virulence factors contributing to the severity of infections caused by different S. aureus clones remain uncertain.

Purpose of the Study:

  • To investigate whether distinct S. aureus clones associated with invasive community-onset infections differ in their virulence.
  • To correlate the genotypic characteristics of S. aureus clones with the clinical severity of invasive infections.

Main Methods:

  • Prospective identification of invasive cMRSA and cMSSA cases.
  • Calculation of an illness severity score (ISS) using principal component analysis of clinical data (mortality, hospital support, bloodstream infection, length of stay).
  • Comparison of mean ISS for each S. aureus clone (MLST-based) with its DNA microarray genotype.

Main Results:

  • Ten S. aureus clones accounted for 77% of the analyzed infections (57 cMRSA, 50 cMSSA).
  • The enterotoxin gene cluster (egc) and collagen adhesin (cna) genes were more prevalent in highly virulent clones.
  • Methicillin-sensitive S. aureus (MSSA) clones were associated with more severe infections than methicillin-resistant S. aureus (MRSA) clones.

Conclusions:

  • The overall genotype of S. aureus isolates, encompassing multiple virulence determinants, likely dictates the clinical severity of invasive infections.
  • Specific virulence factors, such as Panton-Valentine leukocidin (PVL) genes, do not appear to be the sole determinants of infection severity.

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