2.5.2. Bactericidal assay
In vitro bactericidal activity of skin mucus samples were examined against four bacterial strains including common
fish [S. iniae (ATCC29178) and Y. ruckeri (KC291153)] and human [Later monocytogenes (ATCC1143) and E. coli (PTCC 1037)] pathogens. These bacterial strains were obtained from the PersianType Culture Collection, which were prepared as a lyophilized stocks. The disc diffusion method as described by Ref. [22] was used to determine the growth inhibition effect of mucus samples of Caspianwhite fish. At first, selective bacterial were grown in Tryptic soy Agar (TSA) for 24 h at 37 C, and then 0.1 ml of each broth culture medium (contain 1.5 106 c.f.u. ml1 bacteria) was cultured on Mueller Hinton agar. Afterwards, 100 ml of mucus samples were added to sterile paper discs (5 mm in diameter), placed on the medium and newly incubated (25 C, 48 h) [23]. The antibacterial activities were determined by measuring the diameter of zone of inhibition in mm.