Anti-Acanthamoeba effect of potassium isostearate for use as a multipurpose solution

Abstract

Acanthamoeba castellanii is an organism that causes the infection termed Acanthamoeba keratitis (Ishibashi et al., 1988) . The infection was first reported in Britain in 1974(Naginton et al., 1974) and in Japan in 1988(Ishibashi et al., 1988 , and it is estimated that more than hundreds of cases occur each year in contact lens users who are said to represent over 15 million people in Japan so far (Tokoro et al., 2008) . In Japan, the number of young people using soft contact lenses has increased recently (Shinoda et al., 2002; Study Group of National Surveillance of Infectious Keratitis in Japan, 2006) . Acanthamoeba are protozoans found in soil, freshwater, and seawater (Ishii, 1999) . However, non-sterile hands and water can contaminate contact lenses and cause corneal infections (Miyazaki et al., 2007;Yamaura et al., 1993;Zimmerman et al., 2017) .Patients with Acanthamoeba keratitis may experience pain presenting with photophobia, ring-like stromal infiltration, epithelial defects, and eyelid edema (Lorenzo-Morales et al., 2015) . If Acanthamoeba keratitis is not treated adequately, loss of vision may result. Currently, cold disinfection with hydrogen peroxide solution or a multipurpose solution (MPS) is commonly used for disinfecting contact lenses (Hiti et al., 2002;Morishige et al., 2012;Atkins, 2006) . In particular, an MPS can be used to clean, rinse, and disinfect soft contact lenses with the same liquid. In addition, it serves as a preservative, making it a commonly used solution (Hiti et al., 2002;Atkins, 2006) . However, the antiseptic effect of MPS is weaker than that of other disinfection methods, and it is suggested that hypersensitivity may occur (Morishige et al., 2012;Atkins, 2006) . Moreover, according to the 2009 National Consumer Center report in Japan, it has been shown that the anti-amoebic activity of commercially available MPSs is very low