ISO 17721-1:2021 pdf download – Quantitative determination of antibacterial activity of ceramic tile surfaces — Test methods — Part 1: Ceramic tile surfaces with incorporated antibacterial agents.
6 Procedure 6.1 Preparation of test inoculum Transfer the stored bacteria to the nutrient agar slant using a sterile inoculating loop and incubate at 37 ± 1 °C for 16 h to 24 h. Transfer the bacteria to a new nutrient agar slant and incubate at 37 ± 1 °C for 16 h to 20 h. Uniformly disperse a small quantity of test bacteria in 1/500 NB with a platinum loop, and measure the bacteria count using the optical microscope observation method or any other adequate method. Suitably dilute this bacteria suspension with 1/500 NB to obtain a count of 6,7 × 10 5 cfu/ ml – 2,6 × 10 6 cfu/ml and use the result as the bacterial suspension for the test. If the test bacteria suspension is not to be used immediately, store it at 4 °C and use it within 4 h. NOTE See Figure 1 for a flowchart of the test procedure. 6.2? Adhesive? film The adhesive film is inert and non-water absorbent with good sealing properties. The sheets are cut with dimensions of 40 mm ± 2 mm. The film should not affect bacterial growth and can be made of polyethylene, polypropylene or polyester [poly(ethylene terephthalate)]. Film that is 0,05 mm to 0,10 mm thick is recommended. Adhesive film pieces shall be sterilized by autoclave method or surface sterilization by 70 % ethyl alcohol prior to application. NOTE Films cut from Stomacher bags are also suitable.
6.3 Inoculation of test specimens Precondition non-treated control specimens and treated test specimens. Collect exactly 0,15 ml of test bacterial suspension with a sterilized pipette and drip it onto each test piece. Put a film on top of the dripped suspension and lightly push to get the suspension to spread to the whole film surface, while taking care that no suspension leaks out of the film edge. The regulated suspension quantity can create leakage of suspension from the film edge or might not be enough to spread the suspension uniformly. In such a case, it is acceptable to reduce down to half the quantity of suspension or increase to twice the quantity of suspension. However, when the volume of test inoculum is changed, the concentration of the bacterial cells in the inoculum shall be adjusted to provide the same number of bacterial cells as when the normal volume of test inoculum is applied.