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Biosensor for Detection of Antibiotic Resistant Staphylococcus Bacteria
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Biosensor for Detection of Antibiotic Resistant Staphylococcus Bacteria

Published on: May 8, 2013

Detection Methods of Glycopeptide-Resistant Staphylococcus aureus I : Susceptibility Testing

H Hanaki, K Hiramatsu

    Methods in Molecular Medicine
    |March 5, 2011
    PubMed

    Insights

    Vancomycin resistance in Staphylococcus aureus can be heterogeneous, with subpopulations of cells exhibiting reduced susceptibility. These hetero-resistant strains may precede full vancomycin resistance and indicate a risk for treatment failure.

    Area of Science:

    • Microbiology
    • Infectious Diseases
    • Antimicrobial Resistance

    Background:

    • Vancomycin is a critical antibiotic for treating Staphylococcus aureus infections.
    • Methicillin-resistant Staphylococcus aureus (MRSA) poses a significant public health threat.
    • Emergence of vancomycin resistance in S. aureus is a growing concern.

    Purpose of the Study:

    • To investigate the phenomenon of heterogeneous vancomycin resistance in Staphylococcus aureus.
    • To understand the implications of hetero-resistance for vancomycin treatment efficacy.
    • To identify potential risk factors for vancomycin therapeutic failure in MRSA infections.

    Main Methods:

    • Population analysis to define heterogeneous resistance.
    • Minimum Inhibitory Concentration (MIC) testing.
    • Characterization of vancomycin-resistant S. aureus (VRSA) and hetero-resistant strains (e.g., Mu3, Mu50).

    Main Results:

    • The breakpoint for vancomycin resistance in S. aureus is an MIC > 8 μg/mL.
    • The first VRSA strain (Mu50) was isolated from a patient with treatment failure.
    • Hetero-resistant strains (e.g., Mu3) possess subpopulations with high-level vancomycin resistance (up to 9 μg/mL) despite overall susceptibility.
    • Standard MIC and disc susceptibility tests may not detect heteroresistance.

    Conclusions:

    • Heterogeneous vancomycin resistance in S. aureus may represent an intermediate step towards full resistance.
    • Hetero-resistant VRSA strains are a potential risk factor for vancomycin treatment failure in MRSA infections.
    • Further investigation into the mechanisms and clinical significance of hetero-resistance is warranted.

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