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Antonino Asero, Andrea Sudano Roccaro, Loic Favennec, Julie Gueudry, Laetitia Le Goff, Anna Rita Blanco, The Orphan Drug Acanthamoeba Keratitis (ODAK) Group; The efficacy of Polihexanide (PHMB) eye drops against Acanthamoeba polyphaga investigated by an ATP-bioluminescence assay and a rat model of keratitis.. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):1890.
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© ARVO (1962-2015); The Authors (2016-present)
To assess the efficacy of different PHMB concentrations, for potential use in humans, against Acanthamoeba polyphaga using in vitro and in vivo test systems.
In vitro: An ATP-bioluminescence assay was adapted to screen the activity of PHMB against Acanthamoeba polyphaga cysts. Previously viability studies and reported minimal cysticidal concentrations of PHMB, ranging from 0.0001-0.005%, allowed us to select 1:10 and 1:100 dilutions of 4 different PHMB concentrations (0.02, 0.04, 0.06 and 0.08%) to be tested against Acanthamoeba polyphaga cysts for exposure times of 0.5, 1, 3 and 7 hours.<br /> In vivo: Acanthamoeba polyphaga was inoculated into rat corneal stroma and animals treated 4 times a day with PHMB at 0.02, 0.04, 0.06 and 0.08% or with PHMB 0.02% and propamidine 0.1% (combination therapy). Rat corneas were examined and scored clinically every week until day 28. At the end of the experiment superficial corneal epithelium was removed for cultured and PCR and the eye then assessed histologically for Acanthamoeba polyphaga invasion.
In vitro: Killing curves of all the 10-fold dilutions of PHMB concentrations showed the same profile with a 90% reduction of Acanthamoeba polyphaga cyst viability at 3 h. The 100-fold dilutions of 0.04, 0.06 and 0.08% PHMB, showed a 60% reduction of cyst viability. The 100-fold dilution of 0.02% PHMB was the least efficacious with 40% reduction of cyst viability at 3 hours.<br /> In vivo: Monotherapy with 0.02% PHMB drops decreased the clinical severity grading, but not Acanthamoeba polyphaga viability as graded by culture, PCR or histology. Monotherapy with 0.04, 0.06 or 0.08% PHMB, as well as combination therapy, significantly reduced the clinical severity and/or Acanthamoeba polyphaga viability by culture, PCR and histology.
These findings suggest that PHMB 0.02% is less effective than either of the other PHMB concentrations tested, or of combination therapy. However the discriminating power of these test systems could be further improved by the inclusion of more quantitative read outs. We think these are promising test systems for investigating the efficacy of antiamoebic drugs and that their refinement will increase their sensitivity and value in preclinical testing.
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