الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
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Abstract
The use of probiotics as a dietary supplementation provides an alternative way to overcome the adverse effect of antibiotics utilization in aquaculture. Two types of probiotic bacteria were isolated, morphologically and biochemically identified as Pediococcus Pentosaceus and Lactobacillus plantarum. Freshly collected Tilapia zillii and Mugil Seheli from Lake Temsah, Ismailia Governorate and a private farm in Shandora, Suez Governorate were bacteriologically examined for presence of Vibrio species. Twenty four bacterial isolates were morphologically and biochemically identified as Vibrio alginolyticus and Vibrio parahemolyticus. Positive amplicons of Vibrio 16SrRNA gene were detected at 663bp, collagenase gene identified 17 isolate as V.alginolyticus at 737 bp. and seven isolates of V.parahaemolyticus were identified at 368 bp. using toxR gene. Feeding trial of O. niloticus with probiotic supplemented diet revealed significant increase in phagocytosis percent and phagocytic index also the weight gain, specific growth rate, feed conversion rate and protein efficiency ratio increased significantly. Pathogenic challenge with V.alginolyticus strain showed that mortality rate in fish groups (G1 and G 2) received probiotics was 40% and 20% respectively with 100% survivability in G3 that fed on diet with probiotic mixture.