Efficacy of different disinfecting methods for contact lenses against Acanthamoeba castellanii.

Purpose: To analyze the efficacy of different disinfecting methods for contact lenses (CL) against Acanthamoeba castellanii (AC) using quantitative PCR (qPCR) based on RNA detection.

Methods: Three CL materials: rigid gas permeable (RGP), hydrogel (Hy), and silicone hydrogel (SiHy), were contaminated with 1x10⁵ amoebae/ml and incubated for 24 h at 30 °C. After contamination, pre-cleaning steps were performed before using four maintenance solutions based on hydrogen peroxide (HP), sodium hypochlorite (SH), povidone-iodine (PI), and a multipurpose solution (MS). The pre-cleaning steps involved using a cleaner (20 % isopropyl alcohol) and rinsing the CL. Disinfection systems 1 and 2 involved no cleaner and rinsed the CL with tap water or saline solution, respectively. Systems 3 and 4 included a cleaner and rinsed with tap water or saline, respectively. After cleaning, A. castellanii was extracted and stored for qPCR analysis, using Hsp70 and TPBF genes to detect RNA A. castellanii. Results were presented as the percentage of positives or negatives (presence or absence of amoebae), with a p-value < 0.05 considered statistically significant.

Results: Disinfection system 1 with MS resulted in 56 % positives for RGP lenses and 100 % positives for both hydrogel materials. When MS was combined with a cleaner, 12.5 % positives were found for SiHy and 100 % negatives for Hy and RGP lenses (p < 0.05). PI solution alone yielded 38 % and 12 % positives for hydrogel and silicone hydrogel lenses, respectively, but was 100 % effective when combined with a cleaner. HP and SH, whether combined with a cleaner or not, were effective against AC for all CL materials, except HP without a cleaner for Hy lenses.

Conclusion: All disinfection methods showed some efficacy against Acanthamoeba on any CL material. The most effective solutions were those based on hydrogen peroxide and sodium hypochlorite. Using a cleaner enhanced the final disinfecting efficacy, especially with the multipurpose solution.