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Roger Beuerman, Shouping Liu, Rajamani Lakshminarayanan, Jianguo Li, Bai Yang; Small non-hydrophobic, cationic peptide with in vitro and in vivo efficacy against Gram negative bacteria. Invest. Ophthalmol. Vis. Sci. 2013;54(15):4296.
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This study has tested the concept that antimicrobial peptides must include hydrophobic residues in order to show a high level of bacterial killing both in vitro and in vivo.
Two short 8 AA peptides were designed and synthesized in two analogues one with two alanines (088) and one with two glycines (099), these linear peptides were covalentluy linked through the C-terminal lysine. MICs were determined for resistant and sensitive strains of Pseudomonas along with time kill and lab simulations for resistance, membrane interactions with bacteria modeled by molecular dynamics, NMR and finally a mouse model of infection with Pseudomonas ATCC 9027.
MICs using MHB dilution methods showed that the MICs for Pseudomonas, E. coli, and K. pneumonia were 1.5μM for the 099 compound and 2.73 μM for the 088 compound, but the MICs for Staphalococcus aureus were 5.9 and 4.7μM respectively. MICs were determined for 10 clinical isolates of Pseudomonas of which 2 strains were DR and 1 strain MDR (gatifloxicin MICs >22-125μg/ml) while MICS for these as well as 3 clinical E. coli were between 1.5-5.9μM/ml. Laboratory simulations of resistance using Pseudomonas ATCC 9027 with norfloxicin and gentamicin used as comparison showed that resistance was not induced, but was induced in the other antibiotics, MICs increased by 30-140 fold. Both compounds tested on a rabbit model of corneal wound healing of a 5mm dia abrasion showed no differences compared to PBS control. In a mouse model of corneal infection with Pseudomonas with 106 CFU, with gatifloxicin (3mg/ml) used for comparison there was no difference in infection control with B2088/99 at either 1 or 3mg/ml all applications at 5/day.
This new family of non-natural peptides has important characteristics which should be useful for the rapdily emerging problem of antibiotic resistant strains of Gram negative bacteria, especially Pseudomonas
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