Effects of Bacillus subtilis Strains on Growth, Immune Parameters, and Streptococcus iniae Susceptibility in Nile Tilapia, Oreochromis niloticus

Abstract

This study was conducted to evaluate the effects of probiotic‐amended diets fed to juvenile Nile tilapia, Oreochromis niloticus, on growth and susceptibility to Streptococcus iniae infection. Fish (average weight 16.5 ± 0.2 g) were fed five diets formulated with Bacillus subtilis strains SB3086, SB3295, SB3615, or AP193 either individually or in combination of strains SB3086 and SB3615 at a targeted concentration of approximately 4 × 107 colony‐forming units (CFU)/g of feed or with a basal control diet with no additives for 21 d. After the 21‐d growth trial, no significant difference in growth performance was observed with any probiotic‐amended diet. Results from serum bactericidal activity showed a significant difference between treatments and the control (P = 0.0002), except for the SB3295‐amended diet (P = 0.9020). Lysozyme activity was also significantly different in fish fed probiotic diets from those fed control diet (P = 0.0001). After 21 d of feeding, fish were challenged with S. iniae by intraperitoneal injection at a dosage of 8 × 106 CFU per fish. Results from the challenge also showed a significant difference between treatments and control (P = 0.0001). Overall, fish fed with strain SB3615 showed the lowest percent mortality (44.0 ± 7.2%) and those fed the control diet showed the highest mortality (77.3 ± 7.0%). The combined feeding with strains SB3086 and SB3615 did not result in any significant difference in reducing mortality because of S. iniae infection in juvenile Nile tilapia when compared with the individual probiotic treatments.

Assessing the impact ofBacillusstrains mixture probiotic on water quality, growth performance, blood profile and intestinal morphology of Nile tilapia,Oreochromis niloticus

“…The results of the fish serum biochemical analysis in this study reflected a significant increase in globulin accompanied by a signif- (Addo et al, 2017;Liu et al, 2017;Srisapoome & Areechon, 2017;Wang et al, 2017).…”

“…The absence of changes in ALP, GPT and GOT indicates that the probiotic used was safe for the fish metabolic health. The roles of Bacillus ‐based probiotics in enhancing immune status of Nile tilapia have been described in detail elsewhere (Addo et al., ; Liu et al., ; Srisapoome & Areechon, ; Wang et al., ).…”

“…Many studies (Adeoye et al, 2016;Avella et al, 2010;El-Haroun et al, 2006;Liu et al, 2017;Lukkana et al, 2015;Mandiki et al, 2011;Silva et al, 2015;Taoka et al, 2007) demonstrated the ability of Bacillus to colonize the gut of fish and accordingly enhance the production of organic acids, activation of digestive enzymes and detoxification of the harmful constituents of feeds and collectively maintain a healthy gut with a subsequent improvement in nutrient digestibility and absorption. Recently, it was demonstrated that Bacillus can displace pathogenic bacteria from the gut and accordingly enhance disease resistance and improve fish performance (Addo et al, 2017;Hostins et al, 2017;Srisapoome & Areechon, 2017).…”

“…Bacillus-based probiotics improved growth and health, digestive enzymes activities, and the intestinal microbiota and morphology of tilapia. These beneficial effects were demonstrated for Bacillus subtilis (Addo et al, 2017;Liu et al, 2017;Standen et al, 2015Standen et al, , 2016Taoka, Maeda, Jo, & Sakata, 2007) and Bacillus polyfermenticus in tilapia broodstock and fry (Lukkana, Jantrakajorn, & Wongtavatchai, 2015). The beneficial effects of Bacillus amyloliquefaciens in cage-reared tilapia (Silva et al, 2015) and Bacillus pumilus in Nile tilapia reared in captivity and in nature (Srisapoome & Areechon, 2017) were also demonstrated.…”

The effects of dietary Bacillus subtilis on immune response, hematological parameters, growth performance, and resistance of juvenile olive flounder (Paralichthys olivaceus) against Streptococcus iniae

“…Thus, an appropriate concentration of probiotic needs to be included in diets for the successful colonization of the intestine in order to exert beneficial effects. Probiotics have been identified as potential substitutes for antibiotics and chemotherapeutic agents in the control of fish disease in aquaculture practices (Nayak, 2010 (Addo et al, 2017). Enhanced protection against infectious pathogens by probiotics has been mainly attributed to the boosted immune response (Nayak, 2010).…”