Antibacterial activity

This is a quantitative test method in which a bacterial suspension with a defined cell count is applied to the textile and corresponding control material and incubated for 24 hours. The bacteria are then removed by shaking in a neutralizing solution and plated onto counting agar in various dilution levels. The number of bacteria on the control and test material is determined using the colony forming units (CFU). The antibacterial efficacy is calculated from the difference between the growth values of the control and test material.

The test is carried out with the human pathogenic bacterial species Staphylococcus aureus and Klebsiella pneumoniae in order to confirm the effect against both gram-positive and gram-negative bacteria.

The test surfaces and corresponding control materials are inoculated with a bacterial suspension with a defined cell count and spread evenly over an area of 4 cm x 4 cm using a cover sheet. After a contact time of 24 hours, the bacteria are rinsed from the surface with a neutralization solution and plated on counting agar in various dilution levels. The number of living bacteria is determined by counting the colony-forming units. The antibacterial effect is calculated from the difference between the values of the control and test material.

The agar plate diffusion test is a qualitative test method for determining the antibacterial effectiveness of textiles. The textiles are placed on a sewing agar surface inoculated with bacteria and incubated there for 24 hours. Bacterial growth is then assessed using an inhibition zone around the textile and under the sample. The test is carried out with the human pathogenic bacterial species Staphylococcus aureus and Klebsiella pneumoniae to confirm the effect against both gram-positive and gram-negative bacteria.

The minimum inhibitory concentration (MIC) against microorganisms is the lowest concentration of active substance that just barely inhibits pathogen growth. There are various international standards for determining the MIC.

The microdilution method is the reference method and is routinely used in our laboratory. It is a serial dilution test in which geometric dilutions of the test substance are inoculated with test pathogens in a culture medium. After a pathogen-dependent incubation period (generally 18 to 24 hours), the number of still viable test organisms is determined by plate counting against the control samples carried along. The minimum inhibitory concentration is the concentration of the antimicrobial substance at which the initial colony-forming units (CFU) have been reduced by 99.9 % after a 24-hour exposure time. However, as this final value is irrelevant from a clinical point of view for substances that have a germicidal effect within a few minutes to a few hours, the incubation time can be individually adjusted according to customer requirements.