Staphylococcus aureus (S. aureus) is a most important reason for bacterial keratitis. Pathologic and immunologic studies have shown the destruction of the cornea during keratitis. Due to development of methicillin resistance S.aureus (MRSA), discovering new antimicrobial agents for treatments of S.aureus keratitis is desirable. Excretions/secretions (ES) from larvae of maggots (Lucilia sericata) have properties such as protease-resistant, heat stable and antibacterial activity against a wide range of bacteria. The aim of this study is the evaluation of safety and efficacy of larval ES for treatment of S. aureus keratitis.

For ES production, about 500 larvae were washed every hour with 1 ml sterile water. The right eye of four New Zealand rabbits was topically treated with ES each 30 min for three hours (total of seven drops/eye). Ocular toxicity was evaluated using the Draize scoring system. For efficacy evaluation, MRSA was injected intrastromally into rabbit corneas. The rabbits were divided into three treatment groups including Phosphate buffer saline, gentamicin and ES extract. After treatment, the eyes were examined clinically by slit lamp. Finally, the corneas were harvested for colony counts and pathological examinations.

Safety evaluation by Draize testing showed that total score was equal to zero. Efficacy evaluation showed that two treatment groups (ES and gentamicine) were significantly different from the control group (P ≤ 0.05).After treatment, ES and gentamicine significantly reduced CFU and opacity compared with the untreated eyes.

the extraction from larvae of maggots is a safe and effective in treating keratitis mediated by methicillin-resistant S. aureus. Isolation of ES component with antibacterial activity is recommended.