Anti-Acanthamoeba activity of contact lens solutions

Abstract

Aims-This study was undertaken to investigate the eVects of contact lens disinfecting solutions on strains of Acanthamoeba from the United Kingdom and southern Africa and to compare the results with those of other researchers. No information was previously available for southern African isolates. Methods-11 contact lens solutions were tested on cysts of 10 strains of Acanthamoeba. Results-Not all solutions used in the study were eVective, with some for hard and gas permeable contact lenses being more satisfactory than those for soft contact lenses. The most eVective of the gas permeable and hard contact lens solutions tested was Transoak (0.01% (wt/vol) benzalkonium chloride), which killed cysts of all strains within 4 hours of exposure. Oxysept 1 (31 mg hydrogen peroxide/ml) was the best soft contact lens solution tested. It eliminated cysts of certain strains within 4 hours, whereas cysts of other strains were only inactivated within either 8 or 72 hours. Conclusions-Manufacturers should be aware of the killing time for Acanthamoeba by contact lens solutions and should provide appropriate guidelines for the use thereof. The killing time for cysts of the African and UK isolates studied is, in general, similar. Therefore, it must in the present state of knowledge be assumed that usage guidelines suggested in the UK are also appropriate for travellers to South Africa and for local residents in South Africa.

One- and two-step hydrogen peroxide contact lens disinfection solutions against Acanthamoeba: How effective are they?

“…Our results showing the good cysticidal activity of the two-step system Oxysept 1 correspond to those of other studies and can be explained by the long exposure time to 3% hydrogen peroxide which is not deactivated by a catalytic system (tablet or disk). 20,23 Although the Titmus H 2 O 2 system for disinfection of soft and rigid contact lenses works with hydrogen peroxide at a concentration of only 0.6%, it is more effective than the one-step systems, that contain 3% H 2 O 2 , but in that the neutralisation process starts immediately. This shows clearly, that also with 0.6% H 2 O 2 a complete destruction of Acanthamoeba cysts can be achieved, if this concentration is held up during 8 h and not deactivated by a catalytic system.…”

“…Several studies have shown that the sensitivity of Acanthamoeba cysts against contact lens disinfectants varies between the different strains and morphological groups. 19,23,[27][28] Acanthamoeba cysts are slightly smaller than the trophozoites with a size of 12-28 mm in diameter. They are double-walled consisting of an interior endocyst, which can be stellate, polygonal or even round, and an exterior wrinkled ectocyst.…”

Role of fatty acid salts as anti <i>Acanthamoeba</i> agents for disinfecting contact lens

“…Thus, fatty acid salts cannot be adsorbed to the cyst wall, and therefore do not show any anti-amoeba activity in cysts. It has been reported that a lower concentration of disinfecting agents results in reduced effect on cysts Tahara et al, 1997;Niszl and Markus, 1998 . In these reports, benzalkonium chloride was shown to be effective against cysts.…”

How Could Contact Lens Wearers Be at Risk of Acanthamoeba Infection? A Review

“…75 The compliance of contact lens users with the recommended care procedures is ineffective if these solutions do not manage to kill Acanthamoeba. 6,105,109 To avoid the persistent use of non-sterile solutions by non-compliant lens wearers, Moore 13 recommended heat disinfection of lenses-between 70 and 80°C for 10 minutes-and the use of 3% hydrogen peroxide for 2-3 hours, 0.001% thimerosal with edetate for 4 hours, 0.005% benzalkonium chloride with edetate for 4 hours, 0.001% chlorhexidine for 4 hours or 0.004% chlorhexidine for 1 hour. Better compliance of contact lens wearers was achieved with the introduction of multipurpose solutions.…”