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Rajamani Lakshminarayanan, Veluchamy A Barathi, Mayandi Venkatesh, Navin Kumar Verma, Shouping Liu, Xian Jun Loh, Roger W Beuerman; Membrane Selectivity of Cationic Polyamides and Rational Design of Proteolytic-resistant Antimicrobial Peptides. Invest. Ophthalmol. Vis. Sci. 2016;57(12):333. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the antimicrobial properties and mammalian toxicity of cationic polymers with polyamide backbones (P1-P5), evaluate the efficacy of non-cytotoxic polymers in vivo and design antimicrobial peptides based on the most efficacious polymers.
Minimum inhibitory concentration (MIC) of the polymers were determined against a panel of Gram-negative, Gram-positve and yeasts pathogens in accordance with clinical laboratory standards institute (CLSI) protocols. Antimicrobial efficacy in vivo was examined in a rabbit model of infectious keratitis against P. aeruginosa ATCC 9027 and S. aureus 29213 strains. Cytotocompatibility of the polymers was assessed using the primary human dermal fibroblasts by High Content Analysis (HCA).
In vitro microbiological studies indicated that polyamides containing guanidine sidechains displayed weaker antimicrobial acitivity, compared to polyamides containing amine sidechains. Cytotoxicity assays by HCA analysis indicated that all the polyamides (except P5) showed heightened cytotoxicity. Detailed microbiological studies indicated that P5 was active against multi-drug resistant P. aeruginosa, carbapenam-resistant enterobacter, MRSA and VRE (MICs = 8-64 mg/mL in cation adjusted MHB). Time-kill kinetics studies demonstrated that P5 elicited rapid bactericidal activity (>3log10 decrease in <2 h at 4× MIC) against A. baumanii, E. coli, K. pneumonia, P. aeruginosa and PMB-resistant E. cloacae. However, time kill was longer against Gram positive strains (>2-8 h) to achieve similar bactericidal properties. In rabbit model of infectious keratitis, the polymer (0.3% w/v in PBS) displayed similar efficacy against both Gram-positive/-negative strains when compared to Zymar® ophthalmic eye drops. Synthetic peptides designed based on P5 displayed potent antimicrobial activities, retained the activity in the presence of trypsin and were non-cytotoxic to epithelial cells.
In summary, the results established the safety and the potency of P5 as broad-spectrum ophthalmic antibiotics and opened up new avenues in the design of proteolytic-resistant antimicrobial peptides.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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