Bactericidal role of epidermal mucus of freshwater fish treated with Aeromonas hydrophila.

This study explored the bactericidal role of the epidermal mucus (EM) of five freshwater Cyprinid fish species namely Ctenopharyngodon idella, Labeo rohita, Catla catla, Hypophthalmichthys molitrix, and Cirrhinus mrigala after treatment with Aeromonas hydrophila. Extracts of EM (crude and acidic) of each species showed bactericidal activity against various Gram -ve (Pseudomonas aeruginosa, Escherichia coli, Aeromonas hydrophila, Edwardsiella tarda, Salmonella enterica, Klebsiella pneumonia, Serratia marcescens, and Enterobacter cloacae) and Gram +ve (Bacillus wiedmannii and Staphylococcus aureus) bacteria compared with standard antibiotics (Fosfomycin). The zone of inhibition (ZOI) was measured in millimetres against antibiotics (Fosfomycin). Variations in bactericidal activity of EM were observed against bacteria from the same and different fish species. The acidic extract was more effective than the crude extract and showed significantly higher ZOI values against various bacteria and Fosfomycin antibiotics. This result shows that fish EM may perform an important role in fish defence against bacteria. Therefore, this study may hint towards the substitution of synthetic antibiotics with fish EM that may be used as a novel 'bactericidal' in aquaculture as well as in humans against bacterial infections.

Variations in the Behaviour, Survival, Haematology, and Biochemistry of Ctenopharyngodon idella (Grass Carp) After Exposure to Commercial Grade Atrazine.

The current study assessed the harmful effects of Atrazine (ATZ) herbicide on haematology and biochemistry of the freshwater fish Ctenopharyngodon idella, a commercially significant fish in Pakistan. C. idella (13 ± 8.4 cm; 132 ± 5.6 g) was exposed to graded levels of ATZ, and its 96-hour LC50 value at 25°C was calculated to be 150.5 µl/L. After exposure to ATZ, fish displayed rapid movements, a loss of balance in position and equilibrium, anxious swimming patterns, colour changes, and increased mucous production. The MCHC, MCH, RBCs, and Hb in C. idella decreased significantly (P < 0.05), whereas the MCV, Ht, and WBCs were significantly increased (P < 0.05). At different time intervals (24, 48, 72, and 96 h) following ATZ administration (50, 100, 150, and 200 µl/L), biochemical analysis significantly decreased (P < 0.05) triglyceride, total protein, cholesterol, and albumin levels, whereas glucose levels significantly increased (P < 0.05). We concluded that ATZ is toxic to C. idella, altering their haematology and blood biochemistry even after only a brief exposure.