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Experimental Endocarditis Model of Methicillin Resistant Staphylococcus aureus MRSA in Rat
07:46

Experimental Endocarditis Model of Methicillin Resistant Staphylococcus aureus MRSA in Rat

Published on: June 4, 2012

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Early agr activation correlates with vancomycin treatment failure in multi-clonotype MRSA endovascular infections

Wessam Abdelhady1, Liang Chen2, Arnold S Bayer3

  • 1Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA, USA.

The Journal of Antimicrobial Chemotherapy
|January 8, 2015
PubMed
Abstract

Insights

Early activation of the accessory gene regulator (agr) RNAIII in Staphylococcus aureus correlates with persistent endovascular infections despite vancomycin treatment. This finding may help predict treatment outcomes for persistent MRSA infections.

Area of Science:

  • Microbiology
  • Infectious Diseases
  • Molecular Biology

Background:

  • Persistent Methicillin-resistant Staphylococcus aureus (MRSA) infections, particularly endovascular ones, are linked to poor patient outcomes.
  • The specific virulence factors driving MRSA persistence remain incompletely understood.
  • Understanding these factors is crucial for developing effective treatment strategies.

Purpose of the Study:

  • To investigate the correlation between accessory gene regulator (agr) activation and treatment outcomes in a MRSA infective endocarditis (IE) model.
  • To determine if specific MRSA clonal complex (CC) and agr types influence vancomycin treatment efficacy.
  • To identify potential biomarkers for predicting MRSA persistence during endovascular infections.

Main Methods:

  • Evaluated twelve MRSA isolates representing common CC and agr types for heterogeneous vancomycin-intermediate S. aureus (hVISA) status, agr function, and RNAIII transcription.
  • Assessed MRSA virulence and response to vancomycin in an experimental infective endocarditis (IE) model.
  • Analyzed agr locus sequences to identify mutations associated with treatment outcomes.

Main Results:

  • Early and strong agr RNAIII activation, alongside significant δ-haemolysin production, correlated with persistent MRSA infections post-vancomycin therapy in the IE model.
  • Treatment failures occurred across various CC/agr types, irrespective of in vitro vancomycin susceptibility or hVISA/vancomycin tolerance.
  • No common mutations in the agr locus were found to predict temporal RNAIII transcription or vancomycin treatment outcomes.

Conclusions:

  • Temporal agr RNAIII activation and functional profiles may serve as predictive biomarkers for persistent endovascular MRSA infections.
  • These findings highlight the role of agr dynamics in MRSA treatment failure.
  • Further research into agr-mediated virulence could lead to improved therapeutic approaches for challenging MRSA infections.
Keywords:
antibioticsbacteriaresistance

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