Trichophyton mentagrophytes is a dermatophytic fungus which is responsible for causing various forms of tinea infections including athlete’s foot, ringworm, and jock itch. It grows in warm and moist environments and is highly infectious which makes it a significant concern in public spaces and healthcare settings. The ability of this fungus to produce infectious spores makes effective disinfection strategies critical for controlling its spread. Several disinfectants that claim to have antifungal activity are either commercially available or are under development. The AOAC 955.17 dilution test plays an important role in validating the efficacy of these disinfectants.
Why is the AOAC dilution test important?
The AOAC Dilution (AOAC 955.17) test is important for several reasons.
- It ensures the reliability and consistency in results by providing a standardized method to evaluate and compare the effectiveness of disinfectants.
- It helps in the development of products that have antifungal properties and can effectively be used to kill Trichophyton mentagrophytes thereby enhancing infection control measures.
- Successful completion of the test supports the claim of fungicidal activity which is required for regulatory approval and market acceptance of disinfectant products.
What is the AOAC 955.17 Dilution Test?
The AOAC dilution (AOAC 955.17) test is a standard developed by the Association of Official Analytical Chemists (AOAC) International. It is designed to evaluate the fungicidal activity of disinfectants against infectious fungi like Trichophyton mentagrophytes. This test involves culturing the fungus, preparing spore suspensions, and testing various dilutions of the disinfectant to identify the minimum effective concentration. The test’s adaptability allows for customization to meet specific study requirements ensuring broad applicability across different disinfectants and scenarios.
What are the test conditions and requirements?
- Mandatory test strains
As per this standard, Trichophyton mentagrophytes, being a spore producing fungal strain, is recommended to evaluate the efficacy of disinfectants.
- Temperature
Dilutions of the test substance are placed in a recirculating water bath to maintain the test temperature. This ensures consistent conditions for all samples.
- Contact time
A predetermined contact time (as recommended by the manufacturer) between the disinfectant and the fungal spores is required during the test for evaluating the effectiveness of the disinfectant.
- Scope of application
While Trichophyton mentagrophytes is recommended for the test, the standard can be adapted to use other spore-forming fungi.
Test procedure
- Culture preparation- The first step is to culture Trichophyton mentagrophytes to obtain spores producing mycelium.
- Disinfectant dilution preparation- Increasing dilutions of the disinfectant in test tubes or similar containers. These dilutions are then placed in a recirculating water bath to maintain the test temperature. This is to make sure that all the dilutions are uniformly exposed to the test conditions.
- Inoculation with fungal spores- A specific volume of the fungal conidia suspension is added to each disinfectant dilution to ensure an even distribution of spores.
- Contact time – Next, the disinfectant and fungal spores are allowed to interact for a specified contact time as recommended by the manufacturer.
- Neutralization – An aliquot from each dilution is removed and transferred to a neutralizing growth media. This step is carried out to stop the activity of the disinfectant allowing for a precise evaluation of fungicidal efficacy.
- Evaluation of fungicidal activity – Each of the neutralized suspension is then incubated for a specific period under the condition that is suitable for fungal growth. After incubation, the tubes are examined to identify the highest dilution of disinfectant that exhibits no fungal growth. This dilution represents the disinfectant’s fungicidal limit under the given test conditions.
Result interpretation
The dilution of the test substance displaying no fungal growth is considered to be the highest level of dilution that can be used for disinfecting a surface that is supposed to be contaminated with an infectious fungus like Trichophyton mentagrophytes.
Although the AOAC dilution (AOAC 955.17) test provides valuable information on a disinfectant’s fungicidal activity, it is necessary to take into consideration certain factors which can influence the results. These factors include the specific strain of Trichophyton mentagrophytes used, environmental conditions, and variations in disinfectant formulations. Therefore results should be interpreted within the context of these variables.
MIS provides a wide array of fungicidal testing services designed to support various sectors involved in the development of disinfectants, paints/coatings, plastics, and textiles. Our state-of-the-art laboratory facilities, combined with our team of specialists, guarantee precise and dependable results in our offerings.
To inquire about Trichophyton mentagrophytes testing services or to get a quote on AOAC dilution test, please contact MIS experts.
