الفهرس 
Cover Page Title in EnglishOnly 14 pages are availabe for public view
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Abstract
These studies investigated the effect of water quality on the incidence of S. agalactiae in naturally infected seabass during summer season and illustrate the clinical signs and postmortem of S. agalactiae . Use of conventional biochemical characterization and Vitek2 system for identification of S. agalactiae isolated from naturally diseased seabass during summer season. Test the S. agalactiae sensitivity to different antimicrobial agent. Study the control and immunization of sea bass against S. agalactiae. Study the immune status of sea bass challenged by S. agalactiae In our investigation, a total number of one hundred cultured sea bass obtained from private fish farms in Mathalath El-Diba region - Domitte city at Domitte governorate, Egypt during summer season (from August to October 2016). The average body weight was 380 g to 405 g. One hundred and twenty apparently healthy sea bass weighting (25 ± 2 g) which were obtained from a fish farm in Alexandria, Egypt, was used for evaluation the new methods for control of Streptococcosis caused by Streptococcus agalactiae. The fish were kept in aquaria with aerated and filtered seawater (S = 35‰) at 28 ± 2 ºC. The sea bass were kept in the tanks for a few days in order to acclimatize them to the new conditions before the start of the experiment Antimicrobial susceptibility test were carried out on isolated S. agalactiae : Ampicillin, Norfloxacin, Erythromycin, Doxycycline, Flourophenicol and Gentamycin Determination of the immune status of sea bass during evaluation the new methods for control of Streptococcosis caused by Streptococcus agalactiae namely; phagocytic activity and phagocytic index; Nitroblue tetrazolium assay; Lysozyme assay and Total protein and total immunoglobulin in plasma. The present data showed that the Un-ionized form of ammonia; both nitrite and nitrate was significantly higher in the summer season. A hydrogen sulphide value was also higher during summer season and these results were higher than the acceptable level of cultured marine fish The results of heavy metal concentrations during summer season in the water revealed that the all heavy metals were higher than the permissible limits during summer season. Results of clinical signs and postmortem lesions show some of naturally infected seabass showing sever distension of the abdomen and corneal obesity and hemorrhagic patches embedded in liver tissues Some of naturally infected seabass showing sever congestion of the musculature and the abdomen is filled by the bloody exudate.