Abstract
Purpose: :
To evaluate the disinfection efficacy of several multi-purpose solutions (MPS), including a novel Multipurpose Solution, against Acanthamoeba sp. using the ISO 14729 standard.
Methods: :
Testing was performed on several MPS, to evaluate efficacy against both trophozoites and cyst forms, using two different species (Acanthamoeba castellani and Acanthamoeba polyphaga) following the methodology outlined in the ISO standard, modified to allow for Acanthamoeba propagation. Trophozoites and cysts were prepared as challenge inoculum at concentrations of approximately 2X106 amoeba/ml in DPBST (Dulbecco’s Phosphate Buffered Saline with 0.05% Tween). Each formulation was tested three times.
Results: :
Acanthamoebicidal efficacy of the various solutions against trophozoites ranged from 0.34 log reduction to ≥ 4.00 log reduction. Differences in the response magnitude against the trophozoite challenge as measured by log reduction, among the various MPS was also species specific. However, the most substantial differences in the efficacy of the various solutions was observed with the Acanthamoeba cysts. Notably, even when measured at or beyond the manufacturer’s labeled disinfection soak time, some solutions showed minimal biocidal activity against Acanthamoeba cysts.
Conclusions: :
The results, as measured by log reductions, demonstrate that Acanthamoeba test methods derived from the current ISO 14729 bacterial/fungal test standard can clearly distinguish differences in acanthamoebicidal efficacy among representative MPS. The results indicate differences were dependent on the species of Acanthamoeba as well as the life form that was used as the challenge. The results also indicate that the disinfectant(s) used in a MPS system may affect that solution's efficacy against Acanthamoeba. Further study is needed to determine clinical significance of these in vitro results.
Keywords: Acanthamoeba • contact lens • keratitis