Culturability, metabolic activity and composition of ambient bacterial aerosols in a surrogate lung fluid

Area of Science:

• Environmental Health Sciences
• Microbiology
• Toxicology

Background:

• Particulate matter (PM) interactions with the respiratory tract are key to PM-related diseases.
• Research on PM effects often overlooks biological components like bacteria.
• Current methods for assessing bacterial inhalation risk neglect respiratory physiological conditions.

Purpose of the Study:

• To evaluate ambient bacteria using a surrogate lung fluid (SLF) that mimics respiratory conditions.
• To compare bacterial characterization (counts, activity, endotoxin, community structure) using SLF versus phosphate-buffered saline (PBS).
• To determine if standard methods underestimate bacterial inhalation risks.

Main Methods:

• Characterization of ambient bacteria using a surrogate lung fluid (SLF) containing antioxidants.
• Analysis included total bacteria, viable bacteria, culturable bacteria, metabolic activity, endotoxin levels, and community structure.
• Comparison of results obtained using SLF versus phosphate-buffered saline (PBS).

Main Results:

• Phosphate-buffered saline (PBS) underestimated bacterial culturability and metabolic activity compared to SLF.
• Total and viable bacteria counts (intact membrane) were unaffected by the fluid used.
• Bacterial population structure differed, with SLF enhancing recovery of spore-forming bacteria like Bacillus.

Conclusions:

• Standard PBS solutions may lead to underestimation of bacterial inhalation risks, particularly for spore-forming bacteria.
• The use of surrogate lung fluid (SLF) provides a more accurate assessment of bacterial viability and activity in a respiratory context.
• Considering the respiratory airway environment is crucial for accurate microbial inhalation risk assessment.