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Abstract
In this study isolation of vibrio sp. Was done from 4 fish sp. Namelly Oreochromis niloticus, Mugil capito, Mugil cephalus and C. garbensis .
The type of Vibrio sp. were 8 V. anguillarum, 5 V. alginolyticus and 6 untyped .
This was confirmed by both biochemical and API 20E system . The isolated
V. anguillarum which proved to be more virulent than the other isolates for calculating of LD50 which gave value of 10-3.5 .
The isolated Vibrio showed highly sensitive to the following antibiotic chloramphenicol, kanamycin ,streptomycin and oxytetracyclin and resistance to amoxicillin, penicillin G and polymyxin B .
The results of the experimental infection in O. niloticus were :
1. The fish affected by Vibriosis suffered from severe congestion at the base of the fins, erosion on the tips of the fins, excessive mucoid secretion on gills of some, severe congestion of gills and pale gills severe hemorrhagic ulcerations and erosions over the dorsal musculature of the caudal peduncle, linear hemorrhages over different parts of the body, severe congestion or hemorrhagic protrusion of the anal opening, anaemic or pale gills in some samples,
2. At P.M lesions include, Sloughing of gill filament in some parts, bloody distension of gall bladder, bleached or pale areas of the liver, Yellowish colored liver in some samples and congestion in others, enlarged spn and liver, yellowish colored ascetic fluid in the abdominal cavity, severe congestion of internal organs including liver, spn and kidney.
The culture characters of V. anguillarum include : On Trypticase Soya agar : Colonies appear large, 1-4 mm in diameter, white, circular, convex with raised center and glistening appearance. And On MacConkey’s agar : Large, pale, non-lactose fermenter colonies, 3-4 mm in diameter after 24 hour of incubation at 30°C.