ABSTRACT
In vitro screening using methanolic extracts of different marine algae and one sea grass showed antibacterial activity against eight virulent strains of fish and human pathogens I:I [V:V] ratios of each methanolic extract were mutually added to give 21 interactions. The interaction between Udotea sp and Codium fragile extracts exhibited higher activities against Edwardsiella tarda [18 +/- 0.9mm] Vibrio ordalli [16 +/- 0.8mm] Klebsiella pneumonia [20 +/- 1mm] and Pseudomonas aeruginosa [16 +/- 0.8mm]. The bioactivity of this interaction was found to be more effective than that obtained from some common antibiotics including: Lincolin, Streptomycin and Gentamycin. The chemical constituents of these two algal extracts and their interaction were characterized using thin layer chromatography and gas chromatographic - mass spectral analysis. The bioactivity of the separated compounds was estimated. Palmitic acid was the most active fatty acid