Evaluation of a Cationic Antimicrobial Peptide as the New Antibiotic Candidate to Treat Staphylococcus aureus Keratitis

Staphylococcus aureus is a most important reason of bacterial keratitis. The emergence of S. aureus resistance to methicillin necessitates searching for new antimicrobial components for keratitis. CM11 is a cationic peptide with strong antibacterial activity against a range of bacteria. In this study, in vitro bactericidal activity of CM11 was investigated using the time-killing assay. For this purpose, corneal methicillin-resistant S. aureus (MRSA)-infected rabbit models were experimentally developed through intrastromal injection of bacteria. The infected rabbits were treated in three groups by artificial tear, gentamicin, and CM11, and their conjunctiva, iris, and cornea were clinically examined using a slit lamp and histopathological examination. The variance analyses of microbial (colony counts) and pathological examinations on the harvested cornea samples showed a significant improvement in the treated groups (CM11 and gentamicin) compared to the control eyes (P ≤ 0.05). According to findings, CM11 and gentamicin could significantly reduce the CFU in comparison with the group received artificial tear. The mean bacterial counts (log CFU/ml) from corneal culture were 2.1, 5.02, and 8.89 for gentamicin, CM11, and control group, respectively (P ≤ 0.05). The above-mentioned findings displayed the efficacy of CM11 cationic peptide for curing the MRSA-mediated keratitis.