Targeting cyst wall is an effective strategy in improving the efficacy of marketed contact lens disinfecting solutions against Acanthamoeba castellanii cysts

Abstract

A B S T R A C TAcanthamoeba cysts are highly resistant to contact lens disinfecting solutions. Acanthamoeba cyst wall is partially made of 1,4 b-glucan (i.e., cellulose) and other complex polysaccharides making it a hardy shell that protects the resident amoeba. Here, we hypothesize that targeting the cyst wall structure in addition to antiamoebic compound would improve the efficacy of marketed contact lens disinfecting solutions. Using chlorhexidine as an antiamoebic compound and cellulase enzyme to disrupt cyst wall structure, the findings revealed that combination of both agents abolished viability of Acanthamoeba castellanii cysts and trophozoites. When tested alone, none of the agents nor contact lens disinfecting solutions completely destroyed A. castellanii cysts and trophozoites. The absence of cyst wall-degrading enzymes in marketed contact lens disinfecting solutions render them ineffective against Acanthamoeba cysts. It is concluded that the addition of cyst wall degrading molecules in contact lens disinfecting solutions will enhance their efficacy in decreasing the incidence of Acanthamoeba effectively.

Status of the effectiveness of contact lens disinfectants in Malaysia against keratitis-causing pathogens

“…This is likely due to the ability of cellulase to destroy cyst walls by degrading cellulose, allowing chlorhexidine to target the resident trophozoite within and ultimately leading to its death. This is consistent with our previous findings which showed that the addition of cellulase enzyme together with chlorhexidine enhanced the efficacy of contact lens solutions marketed in Pakistan (Abjani et al, 2016). As cellulose synthesis is limited to plants, yeast, and some bacteria, it is likely to have minimal side effects against human cells.…”

“…The supernatant was aspirated followed by addition of 200 μL of six different contact lens disinfectants to resuspend bacteria. Following 6 h of incubation, bacteria were enumerated by plating as described previously (Abjani et al, 2016). Bacteria incubated with PBS alone and bacteria incubated with gentamicin 100 μg per mL were used Table 1 List of contact lens disinfectants tested in the present study together with their ingredients, manufacturer, type of solution and Minimum recommended disinfection time (MRDT).…”

“…The amoebicidal assays were performed as previously described (Abjani et al, 2016). Briefly, contact lens disinfectants were incubated with 5 × 10 5 amoebae (final volume: 200 μL) for 6 h at room temperature as per Manufacturers' instructions.…”

The Development of Drugs against Acanthamoeba Infections

“…It is far more economical to develop effective contact lens disinfectants against Acanthamoeba. Although the ability of amoebae to switch phenotypes into a dormant cyst form is a major hindrance in the development of effective contact lens disinfectants and/or chemotherapeutic approaches, recent studies have shown that the addition of cellulase enzyme to disrupt cyst wall structure renders amoeba cysts susceptible to the effects of antiamoebic drugs (92). The combination of antiamoebic agent and cellulase enzyme was shown to abolish the viability of both cysts and trophozoites.…”

Combating Acanthamoeba spp. cysts: what are the options?

“…Once cyst walls are degraded, it is easier to target Acanthamoeba . This concept was proven by our team [ 13 ] who showed that targeting Acanthamoeba cysts with cellulase enzyme in combination with chlorhexidine can effectively abolish Acanthamoeba cyst viability. In contrast, cellulase or chlorhexidine alone had limited effects against Acanthamoeba cysts [ 13 ].…”