ASTM E3031–15. Standard Test Method for Determination of Antibacterial Activity on Ceramic surfaces.
Test accreditated by ENAC (National Accreditation Entity).
This test method allows the quantitative evaluation of the antibacterial activity of enameled ceramic surfaces that have been specifically designed to contain an antibacterial treatment. This method aims to solve some limitations of the methods ASTM E2180 and ISO 22196, which do not take into account the complexities associated with a ceramic surface, such as the drying of the surface and the use of different chemicals in the composition of the enamel.
In this procedure, the samples are pre-hydrated for 18 to 24 hours before the test. After this period, the enameled ceramic pieces with antibacterial properties and the control pieces (whose enamel does not contain elements with antibacterial properties) are inoculated with a suspension of Escherichia coli of known concentration and incubated for 24 hours. Subsequently, the bacteria are recovered in a neutralizing broth and the count is carried out by plating. The comparison of the logarithmic reductions obtained from the ceramic samples with antibacterials and the control ceramic samples without antibacterials, allows to determine if the antibacterial treatment incorporated in the enamel is considered bacteriostatic, bactericidal, if it produces a partial inhibition or if it does not have any effect on bacterial growth.
The test uses square pieces of 50 mm ± 1 mm. In total 5 pieces are required with the enamel containing the antibacterial element and 10 similar pieces with enamel without antibacterial elements. If it is not possible to have untreated parts, the manufacturer can justify it and supply 10 pieces of glass of the same size. However, in case we had to repeat any part of the test, it is recommended to send twice as many pieces of the indicated number, that is, 30 pieces (10 with antibacterial enamel and 20 with enamel without antibacterial properties).