Molecular analysis of the accessory gene regulator (agr) locus and balance of virulence factor expression in epidemic methicillin-resistant Staphylococcus aureus

J Infect Dis. 2000 Mar;181(3):990-1000. doi: 10.1086/315342.


Potential relationships between virulence factor expression and transmissibility were assessed in epidemic methicillin-resistant Staphylococcus aureus (MRSA) clones CMRSA-1 and CMRSA-3. A major subtype of CMRSA-1 exhibited normal transcription of RNAIII, which facilitates the induction of secreted virulence factors and repression of colonization factor expression at high cell density. However, these isolates characteristically did not express alpha-toxin or protease and displayed a limited profile of secreted proteins. CMRSA-1 also expressed a novel cell surface glycoprotein and exhibited a unique polymorphism within the accessory gene regulator (agr) locus. CMRSA-3 displayed attenuated activation of RNAIII transcription, which was consistent with its higher fibronectin-binding and coagulase activity relative to sporadic MRSA or CMRSA-1 (P=.05), low protease activity, and limited profile of secreted proteins. Thus, the balance of virulence factor expression in CMRSA-1 and CMRSA-3 favors the colonization phase of infection, and CMRSA-1 possesses unique genotypic and phenotypic traits.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / genetics*
  • Chromosome Mapping
  • Electrophoresis, Gel, Pulsed-Field
  • Genotype
  • Membrane Glycoproteins / analysis
  • Methicillin Resistance*
  • Phenotype
  • Polymorphism, Genetic
  • Staphylococcus aureus / classification
  • Staphylococcus aureus / genetics*
  • Staphylococcus aureus / pathogenicity
  • Trans-Activators*
  • Transcription Factors / genetics*
  • Virulence


  • Agr protein, Staphylococcus aureus
  • Bacterial Proteins
  • Membrane Glycoproteins
  • Trans-Activators
  • Transcription Factors