In vitro antimicrobial activity of Shiva-11 against ocular pathogens

Cecropins are antimicrobial peptides (30-35 amino acids) isolated from the hemolymph of the cecropia moth. Previous studies have demonstrated their antimicrobial efficacy against a variety of pathogens, including both gram- positive and -negative bacteria, fungi, protozoa, and enveloped viruses. To assess their therapeutic potential against ocular pathogens, we analyzed the in vitro antimicrobial activity of a synthetic cecropin analog, Shiva-11, against virulent microbial strains (Pseudomonas aeruginosa, Staphylococcus aureus, Streptococcus pneumoniae, and Candida albicans), Bacterial isolates were obtained from human cases of severe ulcerative keratitis. Shiva-11 was tested at varying concentrations in bacterial suspensions containing 1-2 x 10⁶ CFU/ml at 37°C. Samples were plated on nutrient agar and colonies counted after 24-48 h of incubation. Shiva-11 yielded >3 log killing of all isolates after 60 min of exposure to this compound. The results of this study indicate that Shiva-11 possesses broad-spectrum in vitro antimicrobial activity against human clinical ocular pathogens.