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A Fluorescence-based Method to Study Bacterial Gene Regulation in Infected Tissues
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Published on: February 19, 2019

Exotoxin-encoding gene content in community-acquired and hospital-acquired methicillin-resistant Staphylococcus

A E Fossum Moen1, J Saltyte Benth, K Alm-Kristiansen

  • 1Institute of Clinical Epidemiology and Molecular Biology (EpiGen), Akershus University Hospital, Lørenskog, Norway. aina.fossum@medisin.uio.no

Clinical Microbiology and Infection : the Official Publication of the European Society of Clinical Microbiology and Infectious Diseases
|April 28, 2009
PubMed

Insights

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) strains are evolving. Analysis of 821 MRSA isolates revealed distinct toxin profiles differentiating CA-MRSA from hospital-acquired strains, impacting molecular definitions.

Area of Science:

  • Microbiology
  • Infectious Diseases
  • Molecular Epidemiology

Background:

  • Increasing reports of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) in hospital settings raise questions about current molecular definitions.
  • Existing definitions may not adequately characterize all CA-MRSA strains causing infections.

Purpose of the Study:

  • To characterize methicillin-resistant Staphylococcus aureus (MRSA) isolates using multiple typing methods.
  • To investigate the relationship between genetic lineages, exotoxin gene content, and CA-MRSA definitions.
  • To assess the suitability of current molecular criteria for defining CA-MRSA.

Main Methods:

  • Multilocus sequence typing (MLST), staphylococcal cassette chromosome mec (SCCmec) typing, and staphylococcal protein A (spa) gene typing were performed on 821 MRSA isolates.
  • Exotoxin-encoding gene content was analyzed, and cluster analysis was used to group isolates based on these genes.
  • CA-MRSA isolates were defined using MLST type, SCCmec type, and the presence of the Panton-Valentine leukocidin (PVL) gene.

Main Results:

  • Cluster analysis revealed four distinct toxin clusters with varying genetic lineages and diversity.
  • CA-MRSA isolates predominantly grouped into two toxin clusters characterized by a low prevalence of exotoxin-encoding genes.
  • Hospital-acquired MRSA (HA-MRSA) genetic lineages were associated with a higher prevalence of exotoxin-encoding genes.
  • Mobile genetic elements encoding virulence genes appear to be restricted by the genetic background of clonal lineages.

Conclusions:

  • The study supports the theory that virulence gene acquisition is influenced by the host bacterial genetic background.
  • CA-MRSA genetic lineages are characterized by a lower prevalence of exotoxin-encoding genes compared to HA-MRSA.
  • Current molecular definitions for CA-MRSA may need refinement to account for observed variations in exotoxin gene content.

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