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Satya Sree N Kolar, Hasna Baidouri, Vincenzo Luca, Giuseppe Mannino, Maria L Mangoni, Alison M McDermott; Esc1-21 a Novel Antimicrobial Peptide for Microbial Keratitis. Invest. Ophthalmol. Vis. Sci. 2014;55(13):6270.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the antimicrobial efficacy of a novel amphibian antimicrobial peptide, Esculentin1-21 (Esc1-21), in vitro and in a murine model of Pseudomonas aeruginosa (PA) keratitis.
Standard cfu assays were used to determine the MIC of Esc1-21 against PA strains ATCC 27853 and 19660. The effects of physiological salt concentrations and tears (basal and reflex) on anti-pseudomonal activity were also tested. MTT assays were performed to determine if Esc1-21 was toxic to a human corneal epithelial cell line (HCEC). For in vivo studies corneas of C57BL/6 mice were scratched; then 105-106 cfu PA ATCC19660 applied topically. Esc1-21 (40 μM) or PBS was applied topically three times/day for up to 5 days (pi) post-infection. At 1, 3 and 5 days pi, severity of infection was graded by slit-lamp, neutrophil infiltration was assessed by MPO assay and viable bacterial counts were determined.
The MIC for Esc1-21 was 4 μM and 32 μM for ATCC 27853 and 19660 (n=3) respectively. Esc1-21 retained the ability to kill 100% of PA in the presence of 150 mM NaCl (n=3). Killing of PA ATCC 27853 in the presence of 70% v/v human basal or reflex tears was 70% and 94% respectively. MTT assays showed that Esc1-21 was not significantly toxic to HCECs at concentrations of 50 μM and below (n=3). Mice treated topically with Esc1-21 had significantly lower clinical grades (indicating less severe infection) at each time point than PBS treated animals. Normalized MPO and viable bacterial counts were also significantly lower in the Esc1-21 treated animals than the PBS controls at day 3 and 5 pi (n=3).
Esc1-21 is effective against PA in vitro and in vivo, has low toxicity to corneal epithelial cells and retains significant bactericidal activity in the presence of human tears. As antimicrobial peptides do not result in significant pathogen resistance Esc1-21 is a promising candidate for a novel antimicrobial peptide based therapy for microbial keratitis.
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