ISO 20743: 2021. Textiles. Determination of antibacterial activity of textile products.
Test accredited by ENAC (Spanish National Accreditation Entity).
In order to improve the quality of life, some textile products are being treated with antimicrobials to prevent and protect against bacteria. This implies the use of methods to corroborate the existence of antibacterial activity, applicable to textile products with antibacterial finishes, including fabrics, napas, threads and other materials for the manufacture of garments, bedding, domestic furniture and miscellaneous items, whatever the type of antibacterial agent used (organic, inorganic, natural or synthetic) or any of the methods used by manufacturers for their incorporation into the textile product. Initially, the ISO 20645 standard was introduced for the qualitative evaluation of antibacterial activity, for which quantitative methods such as those included in this standard had to be developed. This procedure must be carried out with bacterial species: Staphylococcus aureus and Klebsiella pneumoniae. This standard proposes three methods for inoculating the samples: a) absorption method (direct inoculation of the bacterial suspension in the samples); b) transfer method (the bacteria are placed on an agar plate and transferred from it to the samples); and c) printing method (the bacteria are collected on a filter and printed on the samples). The choice of one or the other of the indicated inoculation methods depends on the properties of the surface of the textile product under test. For the counting of the bacteria in the test products and in the controls, the conventional method of counting CFU (colony forming units) or the ATP-luminescence measuring can be used (measuring the amount of ATP in bacterial cells, expressed in moles of ATP-adenosine triphosphate-). These methods should be applied at times 0 and after incubation from 18 to 24 hours. All tests should include the test product with the antibacterial treatment, as well as a control tissue without antibacterial treatment supplied by the manufacturer. For the method of inoculation by absorption, 0.40 g pieces are required (36 with antimicrobial treatment and 36 without antimicrobial treatment). For the method of transfer inoculation, the same number of pieces of 3.8 cm in diameter are required; and for the printing method, the same number of 60 mm diameter pieces are required. The client must choose, if desired, one or the other of the three inoculation methods indicated, as well as between the two detection methods indicated. In order to consider the result as significant, a reduction in the number of bacteria between 2 and 3 logarithms must be obtained, considering a powerful activity if the value of the reduction is greater than 3 logarithms.