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This electronic Pseudomonas fluorescence is one of the pathogenic bacteria affecting farmed fish in Egypt especially monosex tilapia and Oreochromis niloticus. In this study Monosex tilapia and Oreochromis niloticus infected with isolated strains of P. fluorescence with and without healthy-plus as immunostimulant. LD50, clinical signs in both acute and chronic infections, hematological study to measure the immune status of fish namely phagocytic activity and index, serum enzymes as total protein, albumin and globulin. We examined also, antibody titer and challenge test also carried-out. Pseudomonas infected fish showed skin darkening, loss of scales, tail rot, reddening of the mouth and exophthalmia & congestion of all internal organs .The LD50 was 10-4.5 & 10-2.5 in O.niloticus & Monosex tilapia, respectively .Histopathologically, necrosis and degeneration of liver, spleen, brain and activation of melanomacrophage cells were noticed. Moreover, phagocytic activity and index, total protein , albumin and globulin were decreased. On the other hand, immunostimulants as healthy-plus, decreased the disease susceptibility , increase immune status and antibody titer and the relative level of protection in both O. niloticus and monosex tilapia. Our results cleared that the addition of healthy plus to the fish diets decrease the fish mortality and so, improve the economic return of the fish as the return losses in different groups P. fluorescence Monosex, P. fluorescence + healthy plus Monosex, Control Monosex, P. fluorescence O. niloticus, P. fluorescence + healthy plus O. niloticus and Control O. niloticus reached to 45, 30, 67.50, 45.50, 32.50 and 65 LE/100 marketed fish.