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Published on: May 8, 2013

Detection of virulence-associated genes not useful for discriminating between invasive and commensal Staphylococcus

Holger Rohde1, Matthias Kalitzky, Nicolaus Kröger

  • 1Institut für Infektionsmedizin, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany. rohde@uke.uni-hamburg.de

Journal of Clinical Microbiology
|December 8, 2004
PubMed

Insights

Virulence genes like icaADBC and mecA are common in hospital Staphylococcus epidermidis, making it hard to distinguish invasive from contaminating strains. This challenges using gene detection to predict catheter-related bloodstream infections.

Area of Science:

  • Microbiology
  • Infectious Diseases
  • Medical Device Infections

Background:

  • Staphylococcus epidermidis causes most nosocomial catheter-related bloodstream infections (BSIs).
  • Invasive strains are thought to emerge from less virulent commensal strains selected during catheter insertion.
  • The hospital environment may promote virulence in commensal strains.

Purpose of the Study:

  • To investigate the distribution of virulence-associated genes in S. epidermidis from BSIs and commensal isolates.
  • To compare gene prevalence between invasive BSI strains, commensal strains from bone marrow transplant (BMT) patients, and healthy individuals.
  • To assess the suitability of detecting specific genes for differentiating invasive from contaminating S. epidermidis strains.

Main Methods:

  • Investigated virulence genes (icaADBC, aap, atlE, bhp, fbe, embp, mecA, IS256, IS257), polysaccharide intercellular adhesin synthesis, and biofilm formation.
  • Compared S. epidermidis strains from catheter-related BSIs, BMT patients' commensal isolates, and healthy individuals' commensal isolates.
  • Utilized pulsed-field gel electrophoresis to determine clonal relationships.

Main Results:

  • icaADBC, mecA, and IS256 were more prevalent in BSI isolates than in healthy commensal isolates.
  • No significant difference in gene prevalence was found between invasive BSI strains and clonally independent commensal strains from BMT patients.
  • icaADBC and methicillin resistance contribute to S. epidermidis survival in the hospital environment, increasing device contamination risk.

Conclusions:

  • The presence of icaADBC and mecA in commensal strains within the hospital environment means they cannot reliably distinguish invasive from contaminating S. epidermidis.
  • Virulence factors like icaADBC and methicillin resistance are established early in the hospital environment.
  • Relying solely on detecting icaADBC and mecA is insufficient for predicting catheter-related infections.

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