An Outer Membrane Vesicle-Based Permeation Assay (OMPA) for Assessing Bacterial Bioavailability.

Area of Science:

• Microbiology
• Biophysics
• Drug Discovery

Background:

• Gram-negative bacterial infections require novel antibiotics, necessitating better tools to assess drug permeability and bioavailability.
• Existing methods struggle to accurately predict compound uptake across the complex bacterial cell envelope.

Purpose of the Study:

• To develop and validate an in vitro model using outer membrane vesicles (OMVs) to predict antibiotic permeability across the Gram-negative bacterial cell envelope.
• To compare the predictive capacity of an OMV-based assay with liposome-based assays for antibiotic bioavailability.

Main Methods:

• Utilized outer membrane vesicles (OMVs) from Escherichia coli, modified for porin content, to create a novel in vitro membrane model.
• Characterized the OMV model structurally and functionally using cryo-TEM, SEM, CLSM, SAXS, and light scattering.
• Assessed the in vitro permeability of nine antibiotics using the OMV model and compared results with liposome-based assays and in vivo data.

Main Results:

• The OMV-derived membrane model demonstrated a strong correlation between in vitro permeability and reported in vivo antibiotic accumulation.
• The OMV model successfully discriminated between high and low accumulating antibiotics.
• Liposome-based comparator membranes showed a poor correlation with in vivo data, highlighting the importance of OMV components like porins and lipopolysaccharides.

Conclusions:

• OMV-based in vitro models offer superior predictive capacity for antibiotic bioavailability in Gram-negative bacteria compared to liposome models.
• This approach underscores the critical role of hydrophilic membrane components in antibiotic uptake.
• The OMV assay holds potential as a high-throughput screening tool for identifying promising antibiotic candidates and understanding drug-specific uptake pathways.