Antibacterial properties of the skin mucus of the freshwater fishes, Rita rita and Channa punctatus.

Abstract

OBJECTIVES: The skin mucus of Rita rita and Channa punctatus was investigated to explore the possibilities of its antibacterial properties. MATERIALS AND METHODS: Skin mucus was extracted in acidic solvents (0.1% trifluoroacetic acid and 3% acetic acid) and in triple distilled water (aqueous medium). The antibacterial activity of the mucus extracts was analyzed, using disc diffusion method, against five strains of bacteria--the Gram-positive Staphylococcus aureus and Micrococcus luteus; and the Gram negative Escherichia coli, Pseudomonas aeruginosa and Salmonella typhi. RESULTS: In both Rita rita and Channa punctatus, the skin mucus extracted in acidic solvents as well as in aqueous medium show antibacterial activity against Staphylococcus aureus and Micrococcus luteus. Nevertheless, the activity is higher in acidic solvents than that in aqueous medium. The acidic mucus extracts of Rita rita, show antibacterial activity against Salmonella typhi as well. CONCLUSIONS: The results suggest that fish skin mucus have bactericidal properties and thus play important role in the protection of fish against the invasion of pathogens. Fish skin mucus could thus be regarded as a potential source of novel antibacterial components.