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Padmanabhan Saraswathi, Shouping Liu, Lakshminarayanan Rajamani, Zhou Lei, Charles Tang, Thet T. Aung, Roger W. Beuerman; Antimicrobial Properties of SESB88V against Ocular Pathogenic Staphylococcus Isolates. Invest. Ophthalmol. Vis. Sci. 2011;52(14):1487.
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© ARVO (1962-2015); The Authors (2016-present)
Microbial keratitis is a major disease reported worldwide due to the infection of microorganisms in the cornea of eye with the potential to cause significant visual impairment and blindness. The emergence of multi drug resistance microorganisms necessitates the discovery of new antimicrobial agents for the clinical management of bacterial keratitis and other serious ocular infections. Based upon a novel dimeric peptide SESB88V [(RGRKVVRR)2KK], was synthesized and tested for the eradication of the pathogen. This study was aimed to appraise the antimicrobial property of SESB88V against ocular pathogenic Staphylococcus isolates.
The Minimal Inhibitory Concentration (MIC99) was tested by liquid broth assay by standard methods with the two ocular clinical isolates belongs to Staphylococcus, including one Methicillin resistant Staphylococcus aureus (MRSA). The susceptibility of the peptide was evaluated by time- kill curve analysis at 0.5x, 1x, 2x, 4xMIC using an inoculum of 106 CFU/ml. The mechanism of action of the peptide on the bacteria was studied using Scanning Electron Microscopy (SEM). Toxicity studies using live/dead cell assay were carried out as well.
The MIC of both Staphylococcus isolates was at 12.5 µg/ml. The time kill curve analysis demonstrated the concentration dependent activity with SESB88V at 4xMIC achieved rapid killing within 5 minutes (99.9%) essentially sterilizing the inoculum. The killing time of 2xMIC, 1xMIC, 0.5 MIC was measured at 10,20,30 minutes respectively. The ultra structural observations reveal that the mode of killing mechanism initiated by corrugation in the membrane surfaces. Deep roughening of the bacteria membrane and folds with cavities appearing on the cell surfaces with in minutes of exposure progressed and the bacterial contents were exposed to the environment. Results of toxicity studies with human conjunctiva cells showed little toxicity even at 200µg/ml when compared to gentamicin.
Here we report that SESB88V is safe for human conjunctival cells and has a strong inhibitory action against the ocular pathogens tested. The concentration dependent killing activity of SASB88V shows rapid killing on exposure. In addition the pathological modifications in the structural architecture designate severe, irreversible cell death.
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