Evaluation of the antibacterial activity of skin mucus of three carp species

Abstract

Studies were conducted to evaluate the antimicrobial potency of skin mucus collected from three carp species; <em>Hypophthalmichthys nobilis, Ctenopharyngodon idella</em>, and <em>Cyprinus carpio</em> (exotic to India) against certain human and fish pathogenic bacterial strains viz. <em>Klebsiella pneumoniae, Pseudomonas aeruginosa, Escherichia coli, Staphylococcus epidermidis, Staphylococcus aureus, Bacillus cereus</em>, and <em>Aeromonas hydrophila</em>. The antimicrobial activities were measured in terms of zone of inhibition (ZOI) in mm and compared with two antibiotics (amikacin and chloramphenicol). All selected fish species were also challenged with <em>A. hydrophila</em> through water to check, if there is any change in mucus secretion or its antibacterial effects. Studies have shown that after challenge with <em>A. hydrophila,</em> an increase in mucus secretion was observed in all the three species of carps. Skin mucus extracts (crude and aqueous) obtained from healthy and challenged fish species exhibited strong antibacterial activity against all the investigated microbial strains. Variations in antibacterial effect have been observed among same fish (in healthy and challenged) and amidst different carp species against same and different bacterial strains. In general, crude mucus of all the fish species showed higher bactericidal action than its aqueous extracts and antibiotic chloramphenicol. Hence, these results have clearly revealed that the mucus obtained from fish skin shows antibacterial activity which may play an important role in fish protection against pathogens and thus there appears to be a possibility of using mucus obtained from the skin of carps as an alternative to antibiotics in animals and possibly also in human health related problems.