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Comparative evaluation of hydrogen peroxide sporicidal efficacy by different standard test methods
Simin Sadeghi1, Soosan Abdollahi2, Parastoo Tarighi3
1Department of Drug and Food Control, School of Pharmacy, Tehran University of Medical Sciences, Tehran, Iran.
Iranian Journal of Microbiology
|June 5, 2020
Summary
Comparing sporicidal tests for 7% hydrogen peroxide (H2O2) against Bacillus subtilis spores reveals that higher spore concentrations and interfering substances reduce efficacy. Standard suspension tests in clean conditions are not recommended for verifying sporicidal claims.
Area of Science:
- Microbiology
- Disinfection and Sterilization
- Analytical Chemistry
Background:
- Standardized sporicidal tests vary, impacting the assessment of products claiming sporicidal activity.
- Evaluating the efficacy of disinfectants like 7% hydrogen peroxide (H2O2) requires robust and relevant testing methodologies.
- Bacillus subtilis spores are commonly used as a model organism to assess sporicidal efficacy.
Purpose of the Study:
- To compare the sporicidal efficacy of 7% H2O2 against Bacillus subtilis spores using different standard test methods.
- To evaluate the influence of varying spore concentrations and interfering substances on sporicidal test outcomes.
- To determine the suitability of different test conditions for accurately reflecting real-world product usage.
Main Methods:
- Determined 7% H2O2 sporicidal efficacy against Bacillus subtilis spores using AOAC MB-15-04 carrier test.
- Conducted standard suspension tests (BS EN 13704, AFNOR NF 72-230) under clean and dirty conditions.
- Incorporated interfering substances: bovine serum albumin, yeast extract, and skimmed milk.
Main Results:
- Higher Bacillus subtilis spore concentrations (2 × 10^7 CFU/ml vs. 3 × 10^5 CFU/ml) significantly reduced 7% H2O2 efficacy in suspension tests.
- Interfering substances diminished the sporicidal activity of 7% H2O2, with more pronounced effects at higher spore counts.
- The carrier test required longer contact times compared to suspension tests to achieve sporicidal activity against Bacillus subtilis.
Conclusions:
- The presence of interfering substances and the use of inoculated carriers are recommended to simulate actual product usage conditions.
- Interfering substances can reduce the contact surface between H2O2 and spores, thereby diminishing sporicidal efficacy.
- Standard suspension tests performed in clean conditions are insufficient and strongly discouraged for verifying sporicidal activity claims.
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