A quantitative determination of the antibacterial efficiency of fibrous air filters based on the disc diffusion method

In this study, we fabricated air filters coated with Ag nanoparticles and evaluated their antibacterial efficiencies using colony counting method (CCM) and disc diffusion method (DDM) as a function of Ag nanoparticle content. Two kinds of bacterium Escherichia coli (Gram-negative bacterium), and Staphylococcus epidermidis (Gram-positive bacterium) were tested. As the amount of antibacterial agent increased, the inhibition zone width (IZW), which is the result of DDM, gradually increased and reached the maximum value, while the number of colony forming unit (CFU), which is the result of CCM, decreased and became zero. We derived a correlation equation using the CCM and DDM results, which was used to define the quantitative antibacterial efficiency of the filters according to DDM results.