Achieving consistent multiple daily low-dose Bacillus anthracis spore inhalation exposures in the rabbit model

Area of Science:

• Environmental Science
• Microbiology
• Toxicology

Background:

• Persistent biological agents like Bacillus anthracis spores pose risks from repeated low-level exposures.
• Understanding dose-response relationships requires consistent aerosol generation for inhalation studies.
• Previous methods may lack the precision needed for controlled, low-dose exposures to persistent agents.

Purpose of the Study:

• To evaluate state-of-the-science aerosol methodologies for generating consistent daily low aerosol concentrations.
• To assess the reproducibility of delivering low inhalation doses of Bacillus anthracis spores to rabbits.
• To characterize an aerosol system for its capability in producing controlled, low-dose exposures.

Main Methods:

• A pilot feasibility study characterized the aerosol system's consistency and low concentration capabilities.
• Acute (single-day) and multiple (15-day) exposure studies were conducted using targeted inhaled doses.
• Real-time plethysmography monitored respiratory parameters to ensure dose consistency.

Main Results:

• The aerosol system demonstrated consistency and capability in producing very low Bacillus anthracis spore concentrations.
• Targeted inhaled doses were highly consistent across rabbits and exposure days in all study phases.
• Aerosolized spores were within the optimal size range for deep lung deposition, and the system proved stable and reproducible.

Conclusions:

• The developed animal aerosol system is stable, reproducible, and effective for generating consistent daily low aerosol concentrations.
• This methodology is suitable for delivering precise, low-dose inhalation exposures of persistent biological agents like Bacillus anthracis.
• The system's reliability supports further research into the health effects of repeated low-level exposures to anthrax spores.