Many researches concentrated on development of antimicrobial membranes for many applications such as air or water filtration. Disk diffusion was well-known conventional method for antimicrobial assay. However, this method is preferable to hydrophilic materials, where inhibition zone was easily observed. For hydrophobic materials, negative test was always shown, except increase in antimicrobial loading. In this study, glucose fermentation was introduced as a new method for antimicrobial assay. The survived and viable bacteria either at the surface or attached inside the membranes could ferment glucose resulting in acid production and changing color of indicator in the glucose solution from pale orange to pink. FU8M and FA8M nanofiber membrane, loading with AgNO3 and Benzalkonium chloride (0.3-1.0%) were used as hydrophobic and hydrophilic membrane, respectively. The water absorption of these membranes took 2 h and 2 min, respectively, showing that the latter membrane improved its wettability. It is found that FU8M membrane showed no inhibition zone when the antimicrobial loading less than 1%, whereas the FA8M membrane showed inhibition zone from 8.6-14 mm, depending on antimicrobial loading. However, when glucose fermentation method was used, membranes showed the positive test after 9 hours of incubation at the antimicrobial concentration of 0.5%. Hence, this new method can be used as antimicrobial testing for membrane with simple and cost effective.
Antibiotic action on phagocytosed bacteria measured by a new method for determining viable bacteria.
