National validation study of a cellulose sponge wipe-processing method for use after sampling Bacillus anthracis...

Area of Science:

• Environmental microbiology
• Biothreat agent detection
• Laboratory validation studies

Background:

• Gaps exist in validated methods for biothreat environmental sampling and processing.
• Bacillus anthracis is a significant biothreat agent requiring reliable detection methods.

Purpose of the Study:

• To validate a cellulose sponge wipe-processing protocol for viable Bacillus anthracis Sterne spores.
• To assess the recovery, detection, and quantification of Bacillus anthracis from steel surfaces.
• To characterize the variability of the environmental sampling method.

Main Methods:

• Nine Laboratory Response Network-affiliated laboratories participated.
• Steel coupons were inoculated with Bacillus anthracis Sterne spores (1-4 log(10)).
• Surrogate dust and background organisms were added to mimic environmental conditions.
• Cellulose sponges were used for surface sampling, followed by protocol-based processing.

Main Results:

• Mean percent recovery (%R) ranged from 24.4% to 32.4% across inoculum levels.
• Sensitivity for colony counts reached 84.1% for the lowest inoculum and 100% for higher levels.
• Variability metrics (between-lab, within-lab, total CV) were calculated to characterize method performance.

Conclusions:

• The validated cellulose sponge wipe protocol provides a reliable method for environmental sampling of Bacillus anthracis.
• Characterizing method variability enhances confidence in interpreting environmental sampling results during contamination investigations.
• This study addresses critical needs for validated biothreat detection methods.