Abstract
Studies were conducted to evaluate the antimicrobial potency of skin mucus collected from three carp species; Hypophthalmichthys nobilis, Ctenopharyngodon idella, and Cyprinus carpio (exotic to India) against certain human and fish pathogenic bacterial strains viz. Klebsiella pneumoniae, Pseudomonas aeruginosa, Escherichia coli, Staphylococcus epidermidis, Staphylococcus aureus, Bacillus cereus, and Aeromonas hydrophila. 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 A. hydrophila through water to check, if there is any change in mucus secretion or its antibacterial effects. Studies have shown that after challenge with A. hydrophila, 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.
Highlights
Fishes represent the largest class of aquatic cold blooded vertebrates and form the minor and major links between food webs of the aquatic ecosystems which harbor a wide range of pathogenic organisms (Ellis 2001).Infectious diseases caused by bacteria, viruses and other parasitic organisms are primary concern in aquaculture
The objectives of the present studies were: (1) to analyze the antibacterial effect of skin mucus of three fresh water carp species viz. Hypophthalmichthys nobilis, Ctenopharyngodon idella, and Cyprinus carpio which are exotic to India and cultured in polyculture with indigenous carps, (2) to investigate, if there is any change in mucus secretion and its antibacterial effect after bacterial challenge, and (3) to analyze healthy and challenged fish skin mucus of all three fish species to evaluate the Minimum inhibitory concentration (MIC) against all selected microbial strain for studies
Among all challenged fish species, protein content in mucus of H. nobilis (378.00 ± 3.45 mg ml-1) was higher followed by C. idella (346.66 ± 3.78) and C. carpio (159.78 ± 2.19 mg ml-1)
Summary
Fishes represent the largest class of aquatic cold blooded vertebrates and form the minor and major links between food webs of the aquatic ecosystems which harbor a wide range of pathogenic organisms (Ellis 2001). Infectious diseases caused by bacteria, viruses and other parasitic organisms are primary concern in aquaculture. Effective management of infectious diseases is one of the most critical elements for successful aquaculture (Cooper and Shlaes 2011). The maintenance of large numbers of fish in a small area provides an environment conducive for the development and spread of infectious diseases. Relatively unnatural environment, fish are stressed and more susceptible to diseases. The water environment, and limited water flow, facilitates the spread of pathogens within crowded populations.
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