Abstract
Total bacterial load in body slime, liver and kidney of C. mrigala H. and in pond water were investigated during the period from August, 1993 to April, 1995 in two phases. During the 1st study period (August, 1993 to July, 1994) the mean total bacterial load in surface water was found to vary from 1.39 x 105 (July,'94) to 3.11 x 107 CFU/ml (September, '93), while that of bottom water ranged from 1.01 x 10' (May, '94) to 5.90 x 10' CFU/ml (October, '93). Mean total bacterial load of surface water as recorded during the 2nd study period (November, 1994 to April, 1995) was found to vary from 1.30 x 10' (February,'95) to 0.95 x 10' CFU/ml (April,'95), while that of bottom water ranged from 1.20 x 10" (February,'95) to 0.67 x 108 CFU/ml (March,'95). The mean total number of bacterial load in body slime, liver and kidney was found to vary from 0.58 x 103 (July, 94) to 2.37 x 107 CFU/g (March, '94), from 0.22 x 103 (July,'94) to 9.64 x 106 CFU/g (March, '94) and from 0.15 x 103 (July,`94) to 9.36 x 106 CFU/g (March, '94), respectively. The total bacterial load during the period from November, 1994 to April, 1995 in body slime, liver and kidney was found to vary from 3.26 x 105 CFU/g (December, '94) to 7.2 x 106 CFU/g (March,'95), from 0.2 x 103 CFU/g (February, '95) to 5.05 x 105 CFU/g (March,'95) and from 0.02 x 102 CFU/g (February, '95) to 3.92 x 105
CFU/g (March,'95), respectively. Bacterial load in slime was significantly correlated with bacterial load in liver, bacterial load in slime was significantly correlated with bacterial load in kidney and bacterial load in liver was also significantly correlated with bacterial load in kidney. Micrococcus, Bacillus, Vibrio, Flavobacterium, Acinetobacter, Streptococcus, Nocardia, Enterobacter, Pseudomonas, Aeromonas, Corynebacterium, Moraxella and Staphylococcus and an unidentified bacteria were isolated from the slime, liver and kidney of C. mrigala H. and pond water during the study period. One hundred and seventeen selected bacterial strains belonging to 13 bacterial genera and an unidentified bacteria isolated from body slime, liver and kidney were studied for their sensitivity against Tetracycline, Streptomycin, Chloramphenicol, Ampicillin, Nalidixic acid, Amoxicillin, Kanamycin, Sulpha/Trim, Cotrimoxazole, Novobiocin Gentamycin. It was observed that 100% strains of Aeromonads were resistant to Tetracycline, Ampicillin and Amoxicillin. 70-80% strains of Aeromonads were resistant to Streptomycin, Sulpha/Trim, Contrimoxazole and Novobiocin.
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Abrasion, feeding, injection and immersion methods were used to evaluate the pathogenicity of five different strains of Aeromonas hydrophila viz. RG (Rui gill), ML (Mrigal lesion), SG (Sarpunti gill), Fik (Mrigal kidney), GFL (Gold fish lesion) and Ah-19 (Aeromonas hydrophila-19, Ref. strain) against C. mrigala. H.
Bacterial suspension containing viable cells of 7.5 x 105/ml was found to be very effective in causing 100% mortality after 96 hrs. of inoculation in the form of inter- muscular injection and feeding. The strain RG, ML and Fik produced scale loss with erosion of the skin surface with/without haemorrhagic lesion after 48 hrs. of inoculation following abrasion method. The strains SG and Ah-19 resulted scale loss with erosion of the skin surface with/without haemorrhagic lesion after 72 hrs. of inoculation following abrasion and injection methods. SG and Fik caused reddening in mouth region after 72 hrs. of feeding inoculation, whereas RG resulted frank ulcers from eroded dermal layer exposing underlying musculature which was haemorrhagic after 96 hrs. of inoculation by abrasion method.