الفهرس 
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Abstract
SUMMARY
Pseudomonas oryzihabitans and Ps. luteola were isolated from the intestines
of apparantly healthy Oreochromis niloticus while Proteus vulgaris was isolated
from water samples . Listonella anguillarum and Aeromonas hyDROPhila were
isolated from liver, spleen and kidneys of diseased 0. niloticus. All Ps.
oryzihabitans, Ps. luteola and P. vulgaris revealed antagonistic effect against the
pathogenic Listonella anguillarum in vitro showing the inhibition zones as 30, 5
and 3mm in diameter respectively. P. vulgaris showed antagonistic effect against
the pathogenic Aeromonas hyDROPhila. The inhibition zone was Imm in diameter
in vitro while Ps. oryzihabitans , Ps. luteola and P. vulgaris revealed no
antagonistic effect against the pathogenic Pseudomonas fluorescens. Besides, the
antibiogram revealed that Listonella anguillarum showed resistance to
Kanamycin, Streptomycin, Cefepime ,Colistin and Oxolinic acid.
Congo red and crystal violet binding activity tests were used to detect
virulence in vitro which Pseudomonas oryzihabitans, Ps. Luteola and Proteus
vulgaris appeared non virulent.
At the end of the feeding trial, fish treated with Ps. oryzihabitans as feed
additive showed significantly (PS 0.05) higher final weight, body weight gain,
average daily gain (ADG), specific growth rate (SGR) than control group. The
initial weight and survival rate showed no significant differences (P>0.05).