Effect of different levels of Lactobacillus acidofilus as a probiotic on the anti-bacterial activity of mucus and non-specific immune of mucus in Tiger Barb (Puntius tetrazona)

Fish epidermal mucus and its components provide the first defense line against pathogens. This study was conducted to evaluate the effects of different levels of Lactobacillus acidophilus on antibacterial activity, MIC and some immune parameters of mucus in Puntius tetrazona. Six hundred and thirty fish (0.5 ± 0.03 g) were randomly distributed in 9 aquarium for 3 treatments with 3 replicates (n=70). Fish were fed for 90 days with probiotic supplemented diets (0, 1.5×108and 3×108). At the end of the experiment antibacterial activity against Gram-positive and Gram-negative pathogen Streptococcus faecium and Escherichia coli, respectively, MIC, alkaline phosphatase activity and mucus protein levels were measured. A disk diffusion and microdilution method was used for antibacterial determination. Growth inhibition zone diameters of mucus significantly increased against both bacteria along with increase of probiotic concentration. The serial dilution of 12.5, 25, 50, 100, 200 µl/ml were considered. Alkaline phosphatase activity and mucus protein levels showed a significant differences between probiotic fed fish and control group (P< 0.05).The results showed that the mucus of Puntius tetrazona have an antibacterial activity against the two bacteria strains and fish fed Lactobacillus acidophilus supplemented diet showed elevated mucus antibacterial activity compared fish fed control diet.