BS EN ISO 20743:2021 pdf download.Textiles — Determination of antibacterial activity of textile products.
7.2.3 Glycerol suspension method Inoculate a 15 ml culture tube containing 5 ml of appropriate medium with a freshly grown isolated colony. Incubate, usually, for 5 h to overnight at 37 °C until the bacteria culture seems to reach the late logarithm or stationary phase in the growth curve. For each strain to be stored below −70 °C, for the archives, prepare a sterile, labelled cryogenic vial. Place 225 μl of sterile 80 % glycerol in a cryogenic vial. Add 1,0 ml of the bacterial culture (frozen stock shall be 15 % glycerol). Mix well using the vortex mixer (5.4) and store in a tube at −70 °C or lower. For each strain to be stored at −20 °C, as liquid glycerol working stock, pipette equal volumes of 80 % glycerol and bacterial culture into a labelled polypropylene tube. Mix the contents well to avoid formation of ice crystals that will decrease the viability of the cells. Place the tube in a freezer at −20 °C. Check the viability of the cells after 1 week if possible. To recover a strain from the glycerol stock stored below −70 °C, use a sterile toothpick to scrape pieces of the solid substance, then streak the cells onto the appropriate medium. The frozen stock shall not be thawed because each freeze–thaw cycle will result in a 50 % loss in cell viability. To use the −20 °C working stock, pipette 50 μl to 100 μl as inoculum for a 5 ml overnight culture.
8.1.2 Preparation of test inoculum Adjust the bacteria to a concentration of 1 × 10 5 CFU/ml to 3 × 10 5 CFU/ml by a spectrophotometer or McFarland’s nephelometer (5.1); or adjust the ATP to a concentration of 1 × 10 −9 mol/l to 3 × 10 −9 mol/l by the luminescence method using NB (6.5) or TSB (6.2) after it has been diluted 20 times with water at room temperature. The prepared inoculum shall be preserved by ice-cooling and used within 4 h. 8.1.3 Preparation of test specimens 8.1.3.1 Mass and shape of test specimens 8.1.3.1.1 Obtain test specimens with a mass of 0,40 g ± 0,05 g and cut to a suitable size for test specimens. 8.1.3.1.2 Obtain six test specimens of the antibacterial testing sample and six test specimens of the control fabric or untreated fabric if available. Three of the control specimens and three of the antibacterial testing specimens are used for zero time, immediately after inoculation. The remaining six specimens are used for the contact time after 18 h to 24 h incubation.BS EN ISO 20743 pdf download.