EN 17422: 2022. Quantitative surface test for the evaluation of teat disinfectants in the veterinary area. Test method and requirements (phase 2, step 2).

Test accredited in our laboratory by ENAC (Spanish National Accreditation Entity) with the mandatory bacteria, the yeast Candida albicans and the microorganisms indicated by the BPR Guidance.

The standard EN 17422 specifies a surface test method and requirements for establishing whether a teat disinfectant shows bactericidal activity. This method applies to teat disinfectants that are used on teat skin without mechanical action, as pre-milking and/or post-milking teat disinfectants in the veterinary area, i.e. in the breeding, husbandry, production, veterinary care facilities, transport and disposal of all animals except when in the food chain following death and entry into processing industry.

The test method described by the standard EN 17422 is based on standard EN 16437 (Quantitative surface test for the evaluation of the bactericidal activity of chemical disinfectants and antiseptics used in the veterinary area on porous surfaces without mechanical action - Method and test requirements, phase 2/step 2), but takes into account the practical conditions of application of the products used for teat disinfection, adapting the conditions that may influence their activity in the practical application, including the test surface, contact time and temperature.

The laboratory test according to EN 17422 document uses human synthetic skin as test surface, the microorganisms Escherichia coli and Staphylococcus aureus, a temperature of 30°C, and contact times and interfering substances that vary depending on the whether the test product is a pre-milking or a post-milking disinfectant. For pre-milking disinfection, the test uses a contact time of a minimum of 30 seconds and a maximum of 3 minutes, and bovine albumin as interfering substance. In the test for post-milking disinfection, the minimum contact time is 1 minute and the maximum 5 minutes, whereas milk powder is used for the simulated soiling. The product must be tested at least at three concentrations including one in the non-active concentration range and another in the active concentration range (these last two concentrations are selected by the testing laboratory because they correspond to the internal controls of the test). To consider the test product as bactericidal, it shall demonstrate a 3 decimal log reduction in the bacterial counts for pre-milking disinfectants and a 4 decimal log reduction for post-milking disinfectants.

The procedure described by EN 17422 document has been adapted in our laboratory to evaluate yeasticidal activity with Candida albicans (test accredited under an internal procedure). In our laboratory, the acceptance criterion for demonstrating yeasticidal activity is the one admitted by the EN 16438 standard, that is, a reduction of ≥ 3 log.

Performance of the test following the EN 17422 document, under specific conditions of the BPR Guidance (accredited test in our laboratory):

            The ECHA BPR Guidance indicates that for teat disinfection products, a phase 2- step 2 test must be performed with the following microorganisms: Escherichia coli, Staphylococcus aureus and Streptococcus uberis for bactericidal activity; and Candida albicans for yeasticidal activity. The temperature for testing must be 30ºC or lower. The BPR guidance states that the contact time for pre-milking teat disinfection products is normally 30 seconds or less and should not exceed 60 seconds, while the contact time for post-milking teat disinfection products is normally 1 minute but should not exceed 5 minutes. Regarding the test soiling, tests for pre-milking products should be carried out with either low (3 g/L bovine albumin) or high-level soiling (10 g/L bovine albumin + 10 g/L yeast extract) depending on the instructions given for pre-cleaning procedures. Tests for post-milking products should be carried out with soiling for teat disinfectants (10 g/L skimmed milk).