PURPOSE: A new dual-disinfectant investigational multi-purpose solution (MPS) and 6 currently marketed MPSs were tested for disinfection efficacy against Acanthamoeba trophozoites per ISO 19045-2:2024 methodology.

METHODS: A. castellanii (A.c, ATCC 50370) and A. polyphaga (A.p, ATCC 30461) trophozoites were tested per new ISO 19045-2:2024 methodology. The new investigational MPS (MPS-1, 0.00015% polyquarternium-1 [PQ-1], 0.0003% alexidine dihydrochloride) and 6 marketed products were tested: MPS-2 (polyhexanide hydrochloride 0.0001%); MPS-3 (polyhexanide hydrochloride 0.00011%, alexidine hydrochloride 0.0004%); MPS-4 (0.0006% myristamidopropyl dimethylamine, 0.001% PQ-1); MPS-5 (0.0005% myristamidopropyl dimethylamine, 0.001% PQ-1); MPS-6 (0.0005% myristamidopropyl dimethylamine, 0.001% PQ-1); MPS-7 (0.00016% alexidine dihydrochloride, 0.0003% PQ-1). Per instructions for use, disinfection by MPSs 1-3 was assessed 4 hours post-inoculation and MPSs 4-7 assessed after 6 hours. Acanthamoeba recovery was determined via Spearman-Karber method; log10 reduction values (LRVs) were analyzed by unpaired t-test using Graphpad Prism.

RESULTS: All MPSs tested had efficacy against A. castellanii and A. polyphaga trophozoites. MPS-1 (LRV 3.9) was significantly greater than MPS-2 (LRV 2.7, p=0.006), 4 (LRV 2.6, p=0.007), 5 (LRV 2.8, p=0.04), and 6 (LRV 3.0, p=0.01) at disinfection of A. castellanii ATCC 50370 trophozoites. All MPS tested were not significantly different at disinfection of A. polyphaga ATCC 30461 trophozoites.

CONCLUSIONS: All MPSs demonstrated efficacy against the Acanthamoeba trophozoites tested per ISO 19045-2:2024, but MPS-1 demonstrated greater disinfection against A. castellanii ATCC 50370 compared to 4 currently marketed MPS products. ISO 19045-2:2024 testing confirms MPS-1 effectively disinfects Acanthamoeba trophozoites.