Abstract
The present study assessed the protective aspects of the dietary exposure to black cumin (Nigella sativa, NS) powder on immune response, liver and kidney enzymes, tissue antioxidant capacity, gene expression, and testing the antibacterial activity against Burkholderia cepacia (B. cepacia, BC). Nile tilapia (O. niloticus) (n = 150) were divided into 5 groups, the first was control (Cont) neither challenged nor treated, and fed a basal diet for 59 days. The second one received 30 g kg−1 of NS-incorporated diet and farmed for 45 days (45NS). The third (Cont-BC) and the fourth (14NS-BC) groups were fed a basal diet, while the fifth (59NS-BC) was fed NS-supplemented diet for 45 days. Then, the last three groups were intraperitoneally inoculated with 0.2 mL of virulent BC, and kept under observation for 14 days. During the observation period, Cont-BC group was continuously received a basal diet, while 14NS-BC and 59NS-BC were fed on NS-supplemented diet. Results showed that fish received NS-dietary supplement exhibited significantly (P < 0.05) elevated levels of myeloperoxidase, lysozyme, nitric oxide, superoxide dismutase, and reduced glutathione. A clear modulation was noticed in the levels of cortisol, Malondialdehyde, aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, urea, and creatinine. A clear up-regulation of inflammatory cytokines encoding genes, interleukin 8 (IL-8), interleukin 10 (IL-10), interleukin 1, beta (IL-1β) and immune-related gene, immunoglobulin M (IgM), was evident in NS-enriched groups in comparison to the control. On the contrary, challenged fish with bacterium exhibited a clear decrease in immune and antioxidant (SOD, GSH) biomarkers, while a noticeable increase in hepato-renal parameters, cortisol, and MDA levels, besides gene down-regulation. Thus, we recommend the usage of NS as a nutraceutical to stimulate immunity and as an antibacterial agent in Nile tilapia owing to modulating the immune-antioxidant status, hepato-renal function, and gene expression, besides enhancing the fish survival rates post-exposure to B. cepacia.
•Burkholderia cepacia is a pathogenic systemic bacterium isolated from Nile tilapia.•Nigella sativa powder has antibacterial, antistress, and enhances immunity.•Nigella sativa modulates oxidation, hepato-renal function, and gene expression.•Challenged bacterium alters immune-antioxidant, and down-regulates gene expression.