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Rajamani Lakshminarayanan, Venkatesh Mayandi, Roger W Beuerman, Navin Kumar Verma; The tale of two cationic polymers in a rabbit model of microbial keratitis. Invest. Ophthalmol. Vis. Sci. 2019;60(9):2540.
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© ARVO (1962-2015); The Authors (2016-present)
The ultimate aim of this work is to determine the antimicrobial properties of two cationic polymers, linear polyethyleneimine and epsilon-polylysine in vitro and in vivo.
Standard microbiological broth dilution was carried to determine the minimum inhibitory concentrations of the polymers against a panel of 19 different multi-drug resistant MRSA strains. Time-dependent bactericidal properties (kill kinetics), membrane depolarization (DiSC3-5), SYTOX Green uptake assays were performed to investigate the membrane-permeabilizing properties of the two polymers. Cytotoxicity for conjunctival epithelial cells and conrneal fibroblasts was determined by MTS and high content screening assays. Safety of the polymers for ocular surface was ascertained in porcine/rabbit models of corneal wound healing. The efficacy of the polymers was confirmed in a S. aureus model of infectious keratitis.
Both the polymers displayed potent anti-MRSA activities against all the 19 different clinical isolates. The mean MIC values for εPL (9.1 μg/ml) was superior than LPEI (19.8 μg/ml, p<0.0001) and comparable to that of gatifloxacin (5.1 μg/ml, p>0.05).Both the polymers displayed bactericidal properties against MRSA strains, though LPEI caused a more rapid bactericidal than εPL. Consistent with these results, the two polymers displayed rapid dissipation of membrane potential, uptake of DNA-binding SYTOX Green dye and release of essential intracellular components, indicating membrane targeting properties. Single step resistance frequencies studies indicated low innate resistance (< 10-8) for both the polymers. In co-culture experiments, the two polymers were protective for the mammalian cells against microbial colonization in both prophylactic as well as regression modes. Scratch wound assays indicated that the polymers did not interfere with the cell migration but rescued the adverse effects caused by bacterial secretomes. Topical instillation of the polymers did not affect the regular wound healing of the injured cornea, indicating good biocompatability of the polymers. In rabbit model of S. aureus keratitis, topical instillation of the polymers (4 times/day) decreased the corneal edema, bacterial bioburden and decreased the exaggerated production of pro-inflammatory cytokines.
Taken together experimental observations suggest multiple role of cationic polymers i.e., antimicrobial and anti-inflammatory activities.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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