Well Diffusion Agar Assay (WDAA): Potential probiotic strains isolated using the replica-plating method was further tested for its reproducible antagonistic activity in a well diffusion agar assay (WDAA) against the test pathogens (Mette et al, 2004). The pathogenic bacteria were grown in 4 ml of alkaline peptone water (APW-1g Peptone, 1g Nacl, 100ml distilled water at pH 8.5±0.2) for overnight at 37°C and were mixed with 10 ml of MHA medium at various concentrations (10, 50, and 100 µl). After solidifying, small pits of diameter of 3 mm were made in the culture in the Petri plates and added 10 µl of 48 hrs old probiotic culture grown in marine broth at room temperature to the pits. Plates were incubated in upright position at room temperature for 24 hrs and observed for zone of clearance