Abstract
Purpose :
Biguanides have been shown to have amoebicidal activity against Acanthamoeba species. The addition of biguanides in a multi-purpose solution (MPS) may improve protection from Acanthamoeba Keratitis (AK) associated with contact lens wear (CLW). Testing of Acanthamoeba trophozoites and cysts in an investigational triple disinfectant MPS containing Alexidine, a biguanide, Polyaminopropyl Biguanide (PAPB), and Polyquaternium-1 (PQ-1) was conducted to determine Acanthamoeba disinfection efficacy and to further mitigate risk by assessing the potential for encystment.
Methods :
A. castellanii (A.c, ATCC 50370) or A. polyphaga (A.p, ATCC 30461) trophozoites or cysts were used to prepare an inoculum of 1x107 organisms/ml. For stand-alone disinfection 10 ml of the MPS (3 lots) was inoculated and incubated for 4 hours. For a regimen test, 6 types of contact lenses were inoculated on each surface and allowed to adsorb for 5 minutes. Each lens (N=4) was rubbed for 10 seconds and rinsed for 5 seconds per side. The treated lens was placed in a lens case well with 3 ml MPS (3 lots) and soaked for 4 hours. Recovery of Acanthamoeba was performed by placing test solution (stand-alone) or lens and soak solution (regimen), separately, into neutralizer broth for 10 minutes. Aliquots were serially diluted in a 96-well microtitre plate containing ¼ strength Ringer’s solution. E. coli was added to each well, incubated for 14 days at 26-30oC, and inspected microscopically for recovery. Acanthamoeba recovery values were determined using the Spearman-Karber method and Log10 Reduction (LR) was calculated. Encystment was conducted with A.c trophozoites as directed in ISO 19045.
Results :
Stand-alone disinfection showed a mean LR of 3.8 and 3.7 for A.c and A.p trophozoites respectively and a mean LR of 3.6 and 1.8 for A.c and A.p cysts respectively after 4 hours of disinfection. Regimen disinfection recovery was <0.5 log for A.c and A.p trophozoites, <1.0 log for A.c cysts, and <0.5 log A.p cysts in all 6 lens types tested. No encystment of A.c was detected after incubation in the MPS for 20-24 hours.
Conclusions :
The investigational MPS containing biguanides and polyquaternium-1 showed robust effectiveness of Acanthamoeba trophozoites and cysts in stand-alone, regimen, and encystment testing. Together, these results support that the investigational MPS may reduce the risk of AK associated with CLW.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.