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AOAC Use Dilution Test for Disinfectants
Evaluating the antimicrobial efficacy of disinfectants intended to be used on inanimate surfaces
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Quick understanding of the test
AOAC Use Dilution Test for Disinfectants - Evaluating the antimicrobial efficacy of disinfectants intended to be used on inanimate surfaces
Application
- Salmonella enterica โ AOAC 955.14
- Staphylococcus aureus โ AOAC 955.15
- Trichophyton mentagrophytes โ AOAC 955.17
- Pseudomonas aeruginosa โ AOAC 964.02
- Stainless steel “penicylinders” (carriers) are inoculated with test organisms and dried.
- Contaminated carriers are exposed to disinfectant for a specified contact period.
- Carriers are transferred to a neutralizer/growth medium and incubated.
- Pre- and post-test carrier microbial concentrations are measured.
Benefits
- Ensures disinfectants meet regulatory and performance standards for killing microorganisms on inanimate surfaces.
- Essential for manufacturers to gain product approval from regulatory agencies like the EPA.
Turnaround Time
Passing criteria
- For Salmonella enterica: At least 59 out of 60 carriers must be disinfected.
- For Pseudomonas aeruginosa: At least 54 out of 60 carriers must be disinfected.
- For Staphylococcus aureus: At least 57 out of 60 carriers must be disinfected.
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Abstract
AOAC Use Dilution Test was first developed in 1955. It is a laboratory assay used to determine the efficacy of disinfectants on inanimate surfaces. This test method is specified by the US EPA as the required method for validating disinfectant claims.
AOAC Use Dilution Disinfectant test method uses โpenicylindersโ as carriers. These carriers are inoculated with test organisms and allowed to dry out. After this, inoculated carriers are suspended in a disinfectant solution and finally transferred to a broth growth medium to check the remaining test microorganisms.
Based on the type of the test organisms, AOAC Use Dilution Test methods can be selected and performed โ
- AOAC 955.14 โ Salmonella enterica
- AOAC 955.15 โ Staphylococcus aureus
- AOAC 955.17 โ Trichophyton mentagrophytes
- AOAC 964.02 โ Pseudomonas aeruginosa
AOAC Use Dilution Test (AOAC 955.14, 955.15, 955.17, 964.02) is a very potent test for disinfectant products. In order to pass AOAC Use Dilution Test disinfectant samples must possess good biocidal activity on a shorter contact period.
Organisms typically Used
Staphylococcus aureus (ATCC 6538P), Klebsiella pneumoniae (ATCC 4352), Escherichia coli (ATCC 8739), Pseudomonas aeruginosa (ATCC 15442), Enterococcus hirae (ATCC 10541), MRSA (ATCC 33591), Salmonella enterica (ATCC 10708), Candida albicans (MTCC 3017)
AOAC Use Dilution test method
- 48-hour-old culture of test microorganisms is inoculated and dried on stainless steel mini cylinders (penicylinder) referred to as carriers.
- 60 carriers are required for testing.
- For product samples labeled as one-step cleaners/disinfectants the organic soil is added to the culture before performing the test.
- Three carriers are enumerated to determine pre-test carrier microbial concentrations before transferring to disinfectants.
- Each dry and contaminated test carrier is individually transferred into 10 mL of disinfectant and exposed for a specific contact period time.
- At the end of the contact period, carriers are immediately transferred to the neutralizer/growth medium. Three carriers are enumerated immediately to determine post-test carrier microbial concentrations. While other treated carriers are incubated for 48 hours.
- After incubation, treated carriers are enumerated to estimate the number of viable cells.
- Results are calculated and compared to the following values โ
- For Salmonella enterica โ At least 59 of the carriers must demonstrate complete disinfection
- For Pseudomonas aeruginosa โ At least 54 of the carriers must demonstrate complete disinfection
- For Staphylococcus aureus โ At least 57 of the carriers must demonstrate complete disinfection
Conlcusion
Microbe Investigations (MIS) has world-class equipment and facilities based on the latest technology to perform AOAC Use-dilution tests.
For more information on the AOAC disinfectant testing method, reach out to our experts here. We would be happy to provide you with a quote and solve other related queries.
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Frequently Asked Questions
DR. Martinoz Scholtz
AOAC International (formerly known as the Association of Official Analytical Chemists) is a globally recognized, independent, not-for-profit association that develops and validates analytical methods used by regulatory agencies and industry to ensure the safety and integrity of foods, beverages, dietary supplements and other products.
The dilution method evaluates the ability of disinfectants to kill specific microorganisms at various concentrations. In this method, the test substance (disinfectant) is diluted in a series of decreasing concentrations and exposed to a microbial suspension. The highest dilution that kills the microorganisms is considered the effective concentration.
AOAC Use Dilution test is applicable to liquid-based disinfectants used on hard surfaces.
The AOAC Use Dilution test takes 4-5 days to complete.
We test for AOAC Use Dilution using the following microbial strains: Pseudomonas aeruginosa (ATCC 15442), Escherichia coli (ATCC 8739), Staphylococcus aureus (ATCC 6538P), Enterococcus hirae (ATCC 10541), Klebsiella pneumoniae (ATCC 4352), MRSA (ATCC 33591), Salmonella enterica (ATCC 10708), Candida albicans (MTCC 3017). Additional strains can be added on request.
To pass the AOAC Use-Dilution Method test, a disinfectant must achieve a 99.9% reduction of test organism under specified conditions. Additionally, the product must demonstrate consistent performance over multiple replicates and meet the established regulatory or industry standards for the particular type of microorganism being tested, such as bacteria or fungi.
The AOAC Use-Dilution Method involves testing on hard surfaces mimicking real-world conditions. It is designed to evaluate disinfectant efficacy against specific microorganisms. It is highly standardized, ensuring repeatability and comparability across different laboratories.
No, the AOAC Use-Dilution Method is specifically designed for testing on hard, non-porous surfaces. It may not be suitable for porous surfaces or materials that can absorb the disinfectant which could affect the test results.
The frequency of disinfectant product testing depends on regulatory requirements, product changes, and quality assurance protocols. It should typically be conducted during product development and before the market release. Products should also be tested periodically as a part of ongoing quality control efforts during manufacturing processes.
The AOAC Use Dilution Method is crucial for standardizing disinfectant efficacy testing approaches, ensuring safety of the product, supporting compliance, and building trust in disinfectant products, as it helps manufacturers meet regulatory and industry standards.
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