الفهرس 
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Abstract
The present study was carried out on 180 freshwater fishes, 75 from them were apparently healthy without any clinical signs (40 CI.gariepinusand 35 0. niloticus) and 105 naturally diseased fish (60 agariepinusand 45 O. niloticus) were collected from different localities in Egypt, (El-Reyah El-Tafiki at Benha).
The samples were examined for the isolation of different species of bacteria and fungi most commonly causing disease in fish. The results of bacteriological examination of 75 apparently healthy fish revealed the isolation of 105 different bacterial isolates (65 isolates from Cl. gariepinus and 40 from 0. niloticus) which was identified on the bases of its morphological, cultural and biochemical characters.
The most common isolated bacteria from both fish species was belonging to A. hydrophila species. Thirty isolates of A.hydrophila (46.15%) from Cl. gariepinusand 23 (57.5%) isolates from 0. niloticus. 14 (21.35%) isolates of Ps. fluorescnece from Cl. gariepinusand 7 (17.5%) isolates from 0. niloticus. Ten isolates (15.38%) of Ed. tarda from agariepinusonly. The results revealed the isolation of other types of bacterial isolates but in lower incidence as Proteus sp., Salmonella sp., E.coli and Strept. fecalius.
In case of CL gariepinusthe higher rate of bacterial isolation was from skin (19, isolates) followed by intestine (14), gills (13), liver (8), kidney (5), spleen (4), heart and gall bladder (one, isolate each).
Summary and Conclusion
In case of O.niloticus, the higher rate of the isolation was recorded from the skin (16, isolates) followed by intestine (9), kidney (5), gills, liver and spleen (3) from each and gallbladder, one isolate only.
The bacteriological examination of 105 naturally diseased fishes having clinical and pathogloical alternation (60 CL gariepinusand 45 0. niloticus) resulted in isolation of 120 isolates of different bacteria (72, isolates from Cl. gariepinusand 48, isolates from 0. niloticus).
The identification of the isolated bacteria showed that the most common bacteria isolated was A. hydrophila 25, isolates (34.7%) from CI. gariepinusand 27 isolates (56.25%) from 0. niloticus followed by Ps.flourescence 17, isolates (23.61%) from CL gariepinusand 7, isolates (14.58%) from 0. niloticus, then Ed. tarda 20, isolates (27.7%) from
CLgariepinusonly.
Stmt. fecolis 10 isolates (13.88%) form Cl. gariepinusand 14, isolates (29.16%) from 0. niloticus.
The higher incidence of the isolated bacteria from Cl. gariepinuswas from skin (24, isolates) followed by intestien (17), gills (10), liver (7) spleen and kidney (5, each), heat and gall bladder (2, each). But in 0.niloticus it was found that the high incidence of the bacterial isolated was from the intestine (13, isolates) followed by skin (11), then liver (6), spleen (5), kidney and heart (4, each) gill (3) and gall bladder
(2).
The results of mycotic examination of apparently healthy fishes were represented by the isolates of 80 mycotic isolates from Cl. gariepinusand 45 mycotic isolates from 0. niloticus. The most common
Summary and Conclusion
of isolates were A. niger (21, isolates) a percentage of (33.33%) from Cl. gariepinusand 12 isolates (33.33%) from 0. niloticus followed by A. fundgatus 13 isolates (20.63%) from Cl. gariepinusand 5 isolates (13.88%) from 0.niloticus, then penicillium sp. 8 isolates (12.69%) from Cl. gariepinusand 4 isolates (11.11%) from 0. niloticus. Other types of fungi were isolated but less frequently.
The isolated yeasts were Rh. glutinis 5 isolates (29.41%) from Cl.gariepinusand 4 isolates (44.44%) from 0. niloticus, C. albicans 12 isolates (70.58%) from Cl. gariepinusand 5, isolates (55.55%) from
0.niloticus.
Higher incidence of isolation of fungi recorded from apparently healthy Cl. gariepinuswere from skin (42, isolates) followed by gills (29), kidney (7), liver (2), and in 0. niloticus were from skin (28, isolates) followed by gills (12), liver and kidney (2, each) and one isolate from spleen.
The mycotic examination of 105 naturally diseased fishes having clinical and pathological alternation Cl. gariepinus(60) and 0. niloticus (45) resulted in isolation of different fungi (mold and yeasts). The most common isolated fungi were S. declina 15 isolates (25%) from Cl. gariepinusand 10, isolates (28, 57%) from 0.niloticus followed by A. flavus and S. parasitica 10, isolates (16.66%) (for each) from Cl. gariepinusbut in case of 0. niloticus, the S. parasitica 10, isolates (28.57%) and A. flavus 5, isolates (14.28%). The most common isolated yeasts was Rh. glutinis 12, isolates (20%) from Cl. gariepinusand 5, isolates (14.28%) from 0. niloticus followed by C. albicans 7, isolates (11.66%) from Cl. gariepinusand 3; isolates (8.57%) from 0. niloticus
Summary and Conclusion \ 143
then C. neoformans 6, isolates (10%) from CL gariepinusand 2, isolates (5.71%) form 0. niloticus.
The results also revealed that the high incidence of isolation of fungi (molds and yeasts) from the naturally diseased 0. gariepinuswas from the skin (32, isolates) followed by gills (18), kidney (6), liver and spleen (2, each).
And in the naturally diseased 0. niloticus was the skin (20, isolates) followed by gills (10) kidney (2), liver, intestine and spleen (one, each).
The post-mortem examination of naturally infected Cl. gariepinusshowed a ascitic fluid in the abdominal cavity haemorrhages and enlargement of liver, spleen and kidney. The intestine have petechial hemorrhages, the gills may be congested or inflammed or pale anaemic with encrosis and detachment of gill filaments. Ulcers and necorsis of skin and underlining tissue.
The post-mortem examination of naturally infected 0. niloticus found congestion and hemorrhages in all internal organs in dead fish.
By application of sensitivity test for the most common isolated bacteria as A. hydrophila, Ps. fluorescence, Ed. tarda and Strept. fecales found that the isolated bacteria were sensitive to chlormphenical, nitrofurantoin, tetracycline.