PURPOSE: Currently marketed RGP disinfection products 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. Nine marketed products with RGP disinfection indications were tested: RGP-1 (chlorhexidine gluconate 0.003%, polyaminopropyl biguanide [PAPB] 0.0005%); RGP-2 (chlorhexidine gluconate 0.003%, PAPB 0.0005%); RGP-3 (polyhexamethylene biguanide 0.0005%); RGP-4 (ε-Polylysine 0.01%); RGP-5 (polyquaternium-1 0.0011%); RGP-6 (povidone-iodine 0.05%); RGP-7 (none); RGP-8 (polyhexanide 0.0002%); RGP-9 (Polyhexanide 0.0001%). Per instructions for use, disinfection by RGP-1,2,5,6,7, and 8 were assessed 4 hours post-inoculation; RGP-3 at 5 minutes, RGP-4 at 30 minutes, and RGP-9 assessed after 6 hours. Acanthamoeba recovery was determined via Spearman-Karber method. Log10 reduction values (LRVs) were analyzed with an unpaired t-test using Graphpad Prism.

RESULTS: Products tested varied in their disinfection efficacy against A.c and A.p trophozoites. RGP-1 (LRV 3.9) demonstrated greater disinfection of A. castellanii trophozoites versus RGP-3 (LRV 1.7, p=0.0005), RGP-4 (LRV 2.2, p=0.0002), RGP-5 (LRV 3.1, p=0.03), RGP-6 (LRV 2.7, p<0.0001), RGP-7 (LRV 2.4, p=0.0005), RGP-8 (LRV 1.9, p=0.0002), and RGP-9 (LRV 0.0, p<0.0001). RGP-2 (LRV 4.0) demonstrated greater disinfection of A. castellanii trophozoites versus RGP-3 (LRV 1.7, p=0.0005), RGP-4 (LRV 2.2, p=0.0002), RGP-5 (LRV 3.1, p=0.02), RGP-6 (LRV 2.7, p=0.0001), RGP-7 (LRV 2.4, p=0.0005), RGP-8 (LRV 1.9, p=0.0002), and RGP-9 (LRV 0.0, p<0.0001). RGP-1 (LRV 4.0) demonstrated greater disinfection of A. polyphaga trophozoites versus RGP-3 (LRV 0.7, p=0.003), RGP-8 (LRV 3.0, p=0.03), and RGP-9 (LRV 1.0, p=0.003). RGP-2 (LRV 4.0) demonstrated greater disinfection of A. polyphaga trophozoites versus RGP-3 (LRV 0.7, p=0.003), RGP-8 (LRV 3.0, p=0.03), and RGP-9 (LRV 1.0, p=0.003).

CONCLUSIONS: RGP-1 demonstrated greater disinfection than seven RGP products against A. castellanii and three products against A. polyphaga. RGP-2 demonstrated greater disinfection than seven RGP products for A. castellanii and three for A. polyphaga. Results confirm that RGP-1 (Boston Advanced Conditioning) and RGP-2 (Boston Simplus) products effectively disinfect Acanthamoeba trophozoites.