The Bead Assay for Biofilms: A Quick, Easy and Robust Method for Testing Disinfectants

Area of Science:

• Microbiology
• Biotechnology
• Infectious Diseases

Background:

• Bacteria in biofilms exhibit higher biocide tolerance than planktonic forms.
• Standard disinfectant efficacy tests predominantly use planktonic bacteria.
• Existing methods lack standardization for biofilm biocide testing.

Purpose of the Study:

• Develop and optimize a standardized, repeatable, and cost-effective assay for testing biocide efficacy on bacterial biofilms.
• Evaluate the performance of the new assay using common biocides against Pseudomonas aeruginosa biofilms.

Main Methods:

• Utilized a novel bead assay with glass or polytetrafluoroethylene beads as substrates for biofilm formation in microtiter plates.
• Optimized key assay parameters for ease of handling, speed, and cost-effectiveness.
• Tested the efficacy of glutaraldehyde, isopropanol, and peracetic acid against Pseudomonas aeruginosa biofilms.

Main Results:

• Achieved a 5 log10 reduction in CFU counts with 5% glutaraldehyde (30 min) and 0.3% peracetic acid (10 min).
• 80% isopropanol (30 min) did not meet the target reduction goal.
• Demonstrated reliable repeatability, highlighting the assay's robustness.

Conclusions:

• The developed bead assay provides a robust, quick, and cost-effective method for standardized biocide efficacy testing against biofilms.
• The assay addresses the critical need for reliable biofilm testing, moving beyond planktonic models.
• Results indicate differential efficacy of tested biocides against Pseudomonas aeruginosa biofilms.