Dietary Bacillus subtilis FPTB13 and chitin, single or combined, modulate systemic and cutaneous mucosal immunity and resistance of catla, Catla catla (Hamilton) against edwardsiellosis.

Effects of dietary administration of Bacillus subtilis FPTB13 and chitin, single or combined, on the systemic immunity, mucosal immunity and resistance of catla (Catla catla) against Edwardsiella tarda infection were investigated. The probiotic attributes of B. subtilis was tested by conducting antagonism study, safety in catla, in vitro immunomodulation and dietary immunomodulation. Results of these studies indicated the probiotic potential of the strain. From the preliminary dietary immunomodulation study, a dose of 10(9) B. subtilis cells g(-1) was selected for inclusion into diets for subsequent experiments. Experimental diets were prepared by adding B. subtilis (10(9) cells g(-1)), chitin (2%) and their combination to the basal diet. Different systemic and mucosal immunological parameters viz. oxygen radical production, myeloperoxidase content, lysozyme activity, total protein content and alkaline phosphatase activity showed significant enhancement (p<0.05) after 2 weeks of feeding with the combined diet. B. subtilis and chitin alone also significantly elevated most of the immune responses. All the diets significantly increased the resistance of catla against E. tarda challenge. The highest post-challenge survival was observed in combined group (i.e. 63.33%). In conclusion, B. subtilis and chitin, alone or combined, had a health ameliorating effect in catla. The results also collectively suggest the usefulness of applying a combined probiotic and immunostimulant supplemented diet to achieve greater benefits.