Quantitative test method for the evaluation of sporicidal activity against Clostridioides difficile on non-porous surfaces with mechanical action employing wipes in the medical area (4-field test) - Test method and requirements (phase 2, step 2) (EN 17846: 2023 Standard).
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The EN 17846 standard specifies a carrier test to know if one chemical disinfectant applied with wipes (or mops) has sporicidal activity against spores of Clostridioides difficile. The laboratory test simulates practical conditions of application (contact time, temperature, and interfering substances), including pre-drying specified test organisms on a test-surface (carrier), followed by application of the product on the test-surface with a wipe (or mop). However, if for some applications the recommendations of use of a product differ, additional test conditions may be used.
The products must form a homogeneous, physically stable preparation when diluted with hard water – or in the case of ready-to-use products – with water. The test is applicable to products that are used in the medical area for disinfecting non-porous surfaces including surfaces of medical devices by wiping. The test surface is a standard surface that covers all non-porous surfaces. The test is applicable to areas and situations where disinfection is medically indicated as in patient care, for example: — in hospitals, in community medical facilities and in dental institutions; — in clinics of schools, of kindergartens and of nursing homes; and may occur in the workplace and in the home. It may also include services such as laundries and kitchens supplying products directly for the patients. This test is applicable for four methods of application of products for wiping and/or mopping: a) soaking any non-specified wipe or mop with product; b) spraying the product on any non-specified wipe and / or mop or a specified wipe or mop; c) impregnation of specified wipes or mops by the user with the product according to the manufacturer´s recommendation; d) pre-impregnation of specified wipes or mops by the manufacturer as ready-to-use wipes or mops. In all types, the water control has to be done with a standard wipe, because it is a process or method control.
A test-surface is marked with 4 squares of 5 cm × 5 cm, the “test fields”, in a row. Test field 1 on the test-surface is inoculated with a test suspension of Clostridioides difficile R027 spores in a solution of interfering substances (minimum test conditions). The inoculum is dried. A wipe is soaked with a sample of the product as delivered and/or diluted with hard water (for ready to use products: water). The test-surface is wiped with the soaked wipe across the four marked test fields, starting in front of test field 1, turning immediately after test field 4 and wiped back to the starting point. In parallel a water control is performed: a wipe is soaked with hard water instead of the product.
The product should be tested under conditions simulating the product use, as recommended by the manufacturer. The interfering substance can simulate clean conditions (0,3 g/L bovine serum albumin) or simulated dirty conditions (3,0 g/L bovine serum albumin + 3,0 mL/L sheep erythrocytes) according to its practical applications. Temperature shall be chosen between 4°C and 30°C, and the time of contact is selected depending on the practical conditions for applications of the product. The products for disinfection of surfaces that can go in contact with patients and/or health personnel and the surfaces that are touched by different persons and has the risk of transmission of microorganisms to the patient must be assayed using a time of contact of 5 minutes, maximum. The same considerations are applicable when the time of contact should be limited due to practical reasons. The products for surfaces others than previously mentioned can be assayed with a time of contact of 60 minutes, maximum.
The results shall demonstrate at least a decimal log reduction in counts of 4 on test field 1. The mean of the number of CFU per 25 cm2 on the test fields 2 to 4 shall be equal or less than 50, the mean of the number of CFU on test fields 1 to 4 of the water control shall be equal or more than 10. Additional specific sporicidal activity shall be determined applying other contact times and test organisms in order to take into account intended specific use conditions.
If additional test organisms are used, they shall be incubated under optimum growth conditions (temperature, time, atmosphere and media) noted in the test report. If the additional test organisms selected do not correspond to the specified strains, their suitability for supplying the required inoculum shall be verified. If these additional test organisms are not classified at a reference centre, their identification characteristics shall be stated. In addition, they shall be held by the testing laboratory or national culture collection under a reference for five years.