Bacillus anthracis internalization by human fibroblasts and epithelial cells.

Area of Science:

• Microbiology
• Cell Biology
• Pathogen-Host Interactions

Background:

• The established model for Bacillus anthracis dissemination relies on macrophages as primary host cell carriers.
• Emerging evidence suggests a potential role for additional host cell types in B. anthracis spread.

Purpose of the Study:

• To investigate the internalization of Bacillus anthracis by non-phagocytic human cell lines.
• To explore the mechanisms and host cell dependence of B. anthracis entry into fibroblasts and epithelial cells.

Main Methods:

• Gentamicin protection assays were employed to quantify bacterial internalization.
• Scanning and transmission electron microscopy (EM) provided ultrastructural insights.
• Fluorescence microscopy was utilized to visualize bacterial-host cell interactions.

Main Results:

• Bacillus anthracis spores and vegetative cells adhered to and were internalized by HT1080 (fibroblast) and Caco-2 (epithelial) cells.
• Spore internalization was independent of germination, indicating reliance on spore surface structures.
• Vegetative cell entry was dependent on the growth phase and host cell cytoskeleton, with potential for vacuole escape.

Conclusions:

• Bacillus anthracis can infect non-phagocytic cells, expanding the understanding of its dissemination routes.
• Host cell cytoskeleton actively mediates bacterial entry into fibroblasts and epithelial cells.
• These findings suggest a broader range of host cells involved in B. anthracis pathogenesis than previously recognized.