In vitro antibacterial activity and in vivo safety evaluation of a 11 –amino acids peptide on rabbit eye

One milliliter of clinical Staphylococcus aureus culture isolated from human keratitis were added to 1ml of Muller-Hinton broth containing the peptide in serial 2-fold dilutions( From 1 to 128 µg/ml). The tubes were incubated at 37°C overnight. Antimicrobial activities were expressed as the minimal inhibitory concentration (MIC). For in vivo evaluation, 4 New Zealand rabbits weighing 2.5 to 3.0 kg were used. Right eye were topically treated with 20 µl of MIC and 2xMIC concentration of peptide. Application of cationic peptide continued each 30 min for 3 hours (total of seven drops/eye). Rabbit eyes was examined by slit lamp on day 0 and 24, 48 and 72 hourse after application of peptide. Ocular toxicity was evaluated using the Draize scoring system and confirmed by pathology examination.

The cationic peptide was found to be active against S. aureus with MIC value of 4µg/ml. After treatment of rabbit eye with 4µg/ml and 8 µg/ml of peptide, Draize testing showed that total score was equal to zero for all tests at test time and during 72 h after one. At treatment time, blinking or reflexes not seen in rabbits. Pathology report showed that all tissues including cornea, conjunctiva, sclera, uveal and retina are normal.

The 11-aa peptide is a non-irritant agent in rabbit eye. This peptide can be used as a new antibacterial agent for treatment of infection in eye.