Bacterial Membrane-Derived Vesicles Attenuate Vancomycin Activity against Methicillin-Resistant Staphylococcus aureus

Area of Science:

• Microbiology and Infectious Diseases
• Antimicrobial Resistance
• Bacterial Pathogenesis

Background:

• Methicillin-resistant Staphylococcus aureus (MRSA) is a significant public health threat.
• Vancomycin (VAN) is a critical treatment for severe MRSA infections, but therapeutic failures are increasing.
• Bacterial membrane vesicles (MVs) are emerging as key players in antibiotic resistance.

Purpose of the Study:

• To investigate the impact of MRSA-derived MVs on vancomycin activity against MRSA.
• To assess the effect of MVs on MRSA survival in ex vivo models involving host immunity.
• To characterize MV proteome alterations in response to vancomycin exposure.

Main Methods:

• In vitro assays: Minimum Inhibitory Concentration (MIC) and checkerboard assays.
• Ex vivo models: Whole blood, human neutrophils, and human serum.
• Proteomic analysis of MVs from vancomycin-exposed MRSA.

Main Results:

• MRSA-derived MVs increased vancomycin MICs, correlating with common clinical failure levels.
• MVs enhanced MRSA survival in whole blood and upon exposure to human neutrophils.
• Proteomic analysis revealed elevated expression of MV proteins linked to antibiotic resistance and cell wall metabolism.

Conclusions:

• MRSA-derived MVs significantly reduce vancomycin susceptibility in vitro and ex vivo.
• MVs confer protection against vancomycin and host immune-mediated killing (neutrophils and whole blood).
• Bacterial MVs represent a novel pharmacodynamic factor contributing to vancomycin treatment failures.