| Abstract: |
This study focused on diagnosis of bacterial infection caused by A. hyDROPhila in fish and depending on isolation , identification and specific PCR analysis of this microorganism( A. hyDROPhila ) and detection of the pathogenic aerolysin gene in random isolates of A. hydrohila by its specific primers, also ·detection of 16S rDNA gene in the same random strains by its specific primers , also detection of both genes ( aerolysin and16S rDNA ) by using their primers together by the multiplex PCR.This study applied on 125 fish ( 60 O. niloticus , 20 O. aureus and 45 C. garepinus ) , the examined infected fish showed haemorrahage all over the body specially at the baseof fins , fin rot , detachment of scales , skin ulcers , abdominaldistension - sometimes uni or bilateral exophthalmia and inflammation of anal opening. The postmortem lesions showed congestion of all internalorgans such as ( liver, spleen, kidney) , bloody ascetic fluid inthe abdomen , congested gall bladder and overdistended with bile and sometimes presence of necrotic foci on the liver which showed different colours. ~e prevalence of infection with A. hyDROPhila was 68.8 0/0among the examined fish (73.3% in O. niloticus , 55% in O. aureus, 68.8% in C. garepinus ). According to the biochemical characterization of theobtained A. hyDROPhila isolates , they gave varied results in some of biochemical characters such as Nitrate test, Citrate test and Urease test and Gelatin liquefaction test , where , gave positive results in some isolates and negative results in otherisolates. The results of pathogenicity test in O. niloticus andC. garepinus fingerlings revealed that O. niloticus was moresensitive for infection than C. garepinus.
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