The EN 1650 test method, titled “Chemical disinfectants and antiseptics – Quantitative suspension test for the evaluation of fungicidal activity of chemical disinfectants and antiseptics used in food, industrial, domestic, and institutional areas”, is a European Standard, used to determine the anti-fungal efficacy of chemical disinfectants and antiseptics used in food, industrial, and institutions – excluding those where disinfection is medically indicated. The EN 1650 is similar to ASTM E2315, a suspension time kill procedure.
Briefly, fungal cultures are grown and then inoculated into the liquid test substance. Prior to inoculation of the test substance, the fungal cultures may be diluted with the interfering substance to simulate clean or dirty conditions. The solution is mixed, then allowed to rest for one or more contact times. After contact times elapse, samples of the mixture are neutralized and evaluated using ordinary microbiological dilution and plating techniques. Populations after treatment are compared to controls to determine microbial reduction.
Summary of the EN 1650 Test
- The disinfectant or antiseptic is diluted in hard water to a minimum of three different concentrations. One concentration must be in the product’s active range and one concentration must be in the non-active range. The test solution shall be 1.25x more concentrated than the required test concentration and used within 60 minutes of dilution.
- Using spores from Aspergillus brasiliensis or vegetative cells from Candida albicans, a fungal culture is prepared to a specific concentration and diluted with the interfering test substance, typically Fetal Bovine Serum, to create the test suspension.
- The contact temperature, contact time, and interfering substances is chosen based on the conditions in which the test substance will be used.
- An aliquot of the test suspension is mixed with the test substance and incubated at the appropriate temperature for the selected contact time.
- At the end of the contact time, an aliquot of the test mixture is transferred into an appropriate neutralizer and enumerated.
- Per the method, the test substance needs to demonstrate at least a 4 log (99.99%) reduction.
Strengths of the EN 1650 Test
- EN 1650 can be used for disinfectants that are to be used in a wide range of areas.
- The addition of an appropriate interfering substance creates a more realistic testing environment for the test substance.
Weaknesses of the EN 1650 Test
- This test method excludes disinfectants that are to be used on living tissues or in areas where disinfection is medically indicated.
- Undiluted products can not be tested as some dilution is always produced during the study. The maximum concentration products can be tested at is 80% due to the addition of the inoculum and/or interfering substance.
- This method is not intended for efficacy testing against bacteria.
- The interfering substance that has to be included per the method can make it difficult for a test substance to pass.
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