The present study aimed to assess the impact of probiotic ABM (Activated Beneficial Microorganisms) by1Liter/10m3water on bacteriological, immunological aspects, growth performance, water and fish meat quality and pathological changes of tilapia fish against oxidative stress damage induced by P. aeruginosa. A lab trial was conducted for two months using 130 tilapia fish 15-20g.were divided into four equal groups (out of 10 fish were examined bacteriologically to ensure that they were free from P. aeruginosa and were stocked in four glass aquaria (30 fish per group). All fish were acclimatized for three weeks. G1: kept as control negative, G2: was infected intraperitonially with (0.1×108cfu/ml) P. aeruginosa after 21 days from the beginning of the trial. , G3: was given probiotic ABM from the beginning of the experiment till the end, G4: subjected to add probiotic ABM from the first day till the end of the trial and infected with P. aeruginosa as mentioned before after 21 days from the beginning of the trial. Results revealed that addition of ABM in water aquaria lowered the level of ammonia, increased the dissolved oxygen concentration and growth performance. Body weight of fish showed a significant increase in group fed on ABM and also an improvement of organoleptic properties of tilapia and there were a a significant decrease in total bacterial, psychotropic and Enterobacteriaceae count .In the same aspect addition of ABM achieved an improvement of
TBA&TVN than control and infected group, protein and fat % within the permissible limits in treated groups, and . Significantly decrease of % P. Aeruginosa count and mortality rate in group was treated with ABM. GXP, GST and SOD they were improved and showed an increase in their levels in groups that take ABM. Lysozyme activity and nitric oxide assay
were significantly elevated in P. aeruginosa inoculated group. Meanwhile, the administration of ABM modulated the toxic effect of the bacterial infection, Total serum protein; albumin immunoglobulin showed a significant increase in group fed on ABM with bacterial inoculation. Moreover, albumin and immunoglobulin levels revealed significant increase in group fed on ABM alone which may be due to its immune stimulator and modularity effect. The finding of the present study supports the use of probiotic as immunostimulant in common fish diets. Results of histopathological examination revealed that fish infected with P. aeruginosa showed different pathological changes in gills, skin, muscles, liver, kidneys and gonads