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Debarun Dutta, Nerida Cole, Mark Willcox; Antimicrobial Efficacy of Melimine Covalently Bound to Contact Lenses. Invest. Ophthalmol. Vis. Sci. 2012;53(14):6085.
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There remains a need to reduce microbial contamination of contact lenses, and thus the rate of adverse events during wear. The purpose of the current study was to evaluate antimicrobial efficacyof melimine, a synthetic cationic peptide, against drug resistant and biofilm producer strains of Pseudomonas aeruginosa and Staphylococcus aureus when covalently bound to contact lenses.
Melimine was covalently incorporated into an Etafilcon A contact lens. The amount of peptide present on the lens surface was quantified using dye adsorption. Antimicrobial activity against the bacterial strains was evaluated by measuring the amount of cell death compared to control lenses with no melimine. High salt treatment (10% NaCl) was carried out to extract any adsorbed peptide to ensure that the activity was only due to bound melamine. The stability of the bound peptide to autoclaving at 120ºC for 15 minutes was measured.
There was 7.4 ± 0.7 µg of melimine present on the lens surface. High salt treatment significantly (p<0.05) reduced the amount of adsorbed melimine but affect the antimicrobial activity by only 0.1to 0.2 log. There remained good activity after salt treatment, with contact lenses showing 3.1 log reduction against P. aeruginosa strain 6294 and 3.9 log inhibition against S. aureus strain 31. There were negligible (0.2 to 0.3 log) reductions of antimicrobial activity after heat sterilization. Covalently bound melimine was active against multidrug resistant S. aureus strains 060 and 110, and P. aeruginosa 037, as well as against the strong biofilm producer P. aeruginosa 142, giving 2.4 log, 2.3 log, 4.1 log and 3.4 log reductions in bacterial counts respectively.
Melimine may offer excellent potential for development as a broad spectrum antimicrobial coating for contact lenses, showing strong activity against both gram negative and gram positive organisms which are resistant to antibiotics. The coating is heat stable and thus has the potential to be developed further.
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