Using a Bacterial Pathogen to Probe for Cellular and Organismic-level Host Responses.

Area of Science:

• Microbiology
• Cell Biology
• Infectious Diseases

Background:

• Cytosolic bacterial pathogens, including Listeria monocytogenes (Lm), invade host cells and replicate within the cytoplasm.
• These pathogens degrade vacuolar membranes to access the cytosol and subsequently penetrate the host plasma membrane to infect new cells.

Purpose of the Study:

• To quantify the terminal step of the cellular infection cycle for L. monocytogenes (Lm), specifically host cell penetration.
• To identify pathogen- and host-encoded factors influencing Lm cell-to-cell spread.
• To validate in vitro infection models against in vivo observations.

Main Methods:

• Quantification of Lm host cell exit using colony-forming unit (CFU) assays.
• Flow cytometry to measure Lm infection dynamics and cell penetration.
• Comparison of Lm infection in cultured cells (in vitro) versus murine hepatic cells (in vivo).

Main Results:

• Established and validated quantitative assays (CFU and flow cytometry) for measuring Lm host cell exit.
• Demonstrated the impact of both bacterial and host factors on the cell penetration process.
• Showed strong correlation between in vitro and in vivo Lm infection dynamics.

Conclusions:

• The developed assays provide a robust method for studying bacterial cell-to-cell spread.
• These assays are scalable for high-throughput screening to identify modulators of host cell function during infection.
• The findings support the use of in vitro models for studying Lm pathogenesis and host-pathogen interactions.