Role of fatty acid salts as anti Acanthamoeba agents for disinfecting contact lens.

　Acanthamoeba is found in seawater, fresh water, and soil and is an opportunistic pathogen that causes a potentially blinding corneal infection known as Acanthamoeba keratitis. The anti-amoeba activity of 9 fatty acid salts (potassium butyrate (C4K), caproate (C6K), caprylate (C8K), caprate (C10K), laurate (C12K), myristate (C14K), oleate (C18:1K), linoleate (C18:2K), and linolenate (C18:3K)) was tested on Acanthamoeba castellanii ATCC 30010 (trophozoites and cysts). Fatty acid salts (350 mM and pH 10.5) were prepared by mixing fatty acids with the appropriate amount of KOH. C8K, C10K, and C12K showed growth reduction of 4 log-units (99.99% suppression) in A. castellanii upon 180 min incubation at 175 mM, whereas the pH-adjusted control solution showed no effect. After the amoeba suspension was mixed with C10K or C12K, cell membrane destruction was observed. The minimum inhibitory concentration of C10K and C12K was also determined to be 2.7 mM. Confirmation tests were conducted using contact lenses to evaluate the effectiveness of C10K and C12K as multi-purpose solutions. Experiments using increasing concentrations showed reduced numbers of living cells in C10K (5.5 mM, 10.9 mM) and in C12K (5.5 mM, 10.9 mM). These results demonstrate the inhibitory activity of C10K and C12K against A. castellanii and indicate their potential as anti-amoeba agents.

Antibacterial Effect of Fatty Acid Salts on Oral Bacteria.

Fatty acid salts are a type of surfactant known to have potent antibacterial activity. We therefore examined the antibacterial activities of fatty acid salts against Streptococcus mutans. Potassium caprylate (C10K), potassium laurate (C12K), potassium myristate (C14K), potassium oleate （C18:1K), potassium linoleate (C18:2K), and potassium linolenate (C18:3K), used at a concentration of 175 mM, resulted in a 7 log-unit reduction of S. mutans after a 10-min incubation. The minimum inhibitory concentration (MIC) of C18:2K and C18:3K was 5.5 mM. C12K also demonstrated high antibacterial activity (MIC of 21.9 mM). These results indicate that C12K, C18:2K, and C18:3K have high antibacterial activity against S. mutans, and possess great potential as antibacterial agents.