الفهرس 
Cover Page Title in EnglishOnly 14 pages are availabe for public view
 |  | from | 122 |  |  |
| | | from | 122 | | |
Abstract
This result was carried out to determine the incidence of Vibrio species among the naturally infected Oreochromis niloticus, Mugil cephalus and Clarias gariepinus. In addition to the study of the antibiogram sensitivity of the recovered Vibrio isolates against variable antimicrobial agents. Also, polymerase chain reaction (PCR) was of five Vibrio mimicus isolates with potential diagnostic value. The obtained results of these studies were as follow:
Bacteriological examination of total number of 300 fishes (Oreochromis niloticus, Mugil cephalus and Clarias gariepinus) were as follow:
(1) Oreochromis niloticus: Atotal number of 100 Oreochromis niloticus fishes (50 apparently healthy and 50 naturally infected fishes) were investigated. 16 isolates of Vibrio species with a percentage of 32% were recovered from apparently healthy fishes. However, the recovery rate of Vibrio species from naturally infected Oreochromis niloticus fishes were 56% (28 isolates).
(2) Mugil cephalus: A total number of 100 Mugil cephalus fishes (50 apparently healthy and 50 naturally infected fishes) were investigated. Vibrio species were recovered from apparently healthy Mugil cephalus fish with an incidence of 36% (18 isolates). On the other hand, the recovery rate of Vibrio species from naturally infected Mugil cephalus were 52%, where 26 isolates of Vibrio species were recovered from various internal organs of fish.
(3) Clarias gariepinus: A total number of 100 Clarias gariepinus fishes (50 apparently healthy and 50 naturally infected fishes) were investigated. 6 isolates of Vibrio species with a percentage of 12% were isolated from apparently healthy Clarias gariepinus fishes. While the isolation rate of Vibrio species from naturally infected Clarias gariepinus fishes were 32% (16 isolates).
The isolation and identification of Vibrio species were carried out by using the trypticase soya agar (TSA)(3%) and the specific medium thiosulphate citrate bile salt sucrose agar (TCBS) and the traditional biochemical tests for identification. Morever API 20E system were also used for identification. Two methods of identification were parallel to each other and the results were as follow:
(1) Oreochromis niloticus: 16 isolates from apparently healthy fishes were identified as follow: 12 isolates were Vibrio fluvialis and 4 isolates were Vibrio splendidus,while the total number of recovered Vibrio species from naturally infected Oreochromis niloticus fish were 28 isolates (18 isolates Vibrio mimicus and 10Vibrio parahaemolyticus).
(2) Mugil cephalus: A total number of 44 isolates of Vibrio species were recovered from apparently healthy and naturally infected Mugil cephalus fishes (18 and 26 isolates respectively). The recovered isolates from apparently healthy fishes were (9 Vibrio mimicus, 5Vibrio parahaemolyticus and 4 Vibrio fluvialis). On the other hand, the isolates obtained from naturally infected fishes were identified as follow: 15 Vibrio mimicus, 7 Vibrio parahaemolyticus and 4 Vibrio splendidus.
(3) Clarias gariepinus: Regarding apparently healthy Clarias gariepinus fishes, the recovered isolates were 6 isolates identified as follow (4 Vibrio fluvialis and 2 Vibrio splendidus). Meanwhile, the total number of Vibrio isolates recovered from naturally infected Clarias gariepinus were 16 isolates identified as follow (9 Vibrio mimicus, 3 Vibrio parahaemolyticus and 4 Vibrio fluvialis).
Polymerase chain reaction (PCR) of Vibrio specieswas positive as the agar gel electrophoresis of the PCR products showed that all the eight isolates tested produced a DNA band at 663 base pair. And polymerase chain reaction of V.mimicuswas positive as the agar gel electrophoresis of the PCR products showed that six isolates of twenty isolates tested produced a DNA band at 121 base pair.
The antimicrobial sensitivity test of 18 isolates of Vibrio species were recorded against different 13 antimicrobial agents. It was recorded that all the tested isolates were highly sensitive to chloramphenicol with a percentage of 100%. However, only 15 isolates were sensitive to ampicillin with an incidence of 83.33%. In contrast all isolates were highly resistant to penicillin while variable resistance noted with the following antimicrobial agents: nalidixic acid, streptomycin, trimethoprim-sulphamethoxazole, amoxicillin, kanamycin, gentamycin and oxytetracycline.