Antimicrobic Activity and Action Mechanism of silver(I)-Exchanged Zeolites

Siver(I)-loaded zeolites, prepared from both pure and impure zeolites in sodium form, were investigated to establish their antimicrobic activity against Candida albicans, Staphylococcus aureus and Salmonella typhi microorganisms, which are representative of yeasts, gram-positive and gram-negative bacteria respectively. Antimicrobic activity was found to be very rapid for S. typhi, slightly less rapid for S. aureus and C. albicans and in all cases strongly dependent on the concentration of the free silver (I) ion. Antimicrobic activity decreases considerably in the presence of silver (I) precipitating or complexing agents, such as chloride or thiosulphate. Zeolites work by releasing controlled amounts of silver ion without any interference with biocidal avtivity.