Caffeine supplementation in diet mitigates Aeromonas hydrophila-induced impairment of the gill phosphotransfer network in grass carp Ctenopharyngodon idella

Preparation and characterization of glucose-conjugated super-paramagnetic iron oxide nanoparticles (G-SPIONs) for removal of Edwardsiella tarda and Aeromonas hydrophila from water

The present research was conducted to prepare efficient G-SPIONs by co-precipitation to remove Edwardsiella tarda and Aeromonas hydrophila from the aqueous solution. The synthesized G-SPIONs were characterized by UV-Vis spectrophotometer, DLS, FEG-TEM, FT-IR, XRD, and VSM analysis. The results showed that the synthesized G-SPIONs had super-paramagnetic properties (58.31 emu/g) and spherical shape (16 ± 3 nm). The antibacterial activity was assessed in sterilized distilled water at different G-SPIONs concentrations viz. 0, 1.5, 3, 6, 12, 24, 48, 120, and 240 mg/L against E. tarda and A. hydrophila with various bacterial loads viz. 1 × 10³ , 1 × 10⁴ , 1 × 10⁵ , 1 × 10⁶ , and 1 × 10⁷  CFU/ml at different time intervals 15, 30, 45, and 60 min. At a lower bacterial load of E. tarda and A. hydrophila 1 × 10³ -1 × 10⁴  CFU/ml, 100% bacterial load was removed by 15 min exposure with NPs concentration 6-48 mg/L and 1.5-6 mg/L, respectively. Cent percent bacterial removal was observed in both the bacterial species even at higher bacterial load (1 × 10⁵ -1 × 10⁷  CFU/ml) by increasing exposure time (15-60 min) and nanoparticle concentration as well (24-240 mg/L). At an initial bacterial load of E. tarda and A. hydrophila (1 × 10³ -1 × 10⁷  CFU/ml), the EC₅₀ ranged between 0.01-6.51 mg/L and 0.02-3.84 mg/L, respectively, after 15-60 min exposure. Thus, it is concluded that the antibacterial effect of G-SPIONs depends on concentration and exposure time. Hence, G-SPIONs can be used as an antibacterial/biocidal agent to treat Edwardsiellosis and Aeromonosis disease in aquaculture.

Effects of thymol supplementation on performance, mortality and branchial energetic metabolism in grass carp experimentally infected by Aeromonas hydrophila

We determined whether thymol supplementation of would minimize the negative effects of Aeromonas hydrophila infection on branchial energy metabolism, weight loss and mortality in grass carp (Ctenopharyngodon idella). We found that the infected fish all died, while 62.5% of those supplemented with 100 mg/kg thymol survived. Cytosolic and mitochondrial creatine kinase (CK) activities, as well as adenylate kinase (AK) and pyruvate kinase (PK) activities were significant lower in gills of A. hydrophila-infected fish than those of the control group, and adenosine triphosphate (ATP) levels were significant lower in the infected group. Finally, branchial reactive oxygen species (ROS) were significant higher in A. hydrophila-infected fish than in the control group. Supplementation with 100 and 300 mg thymol/kg diet prevented inhibition of branchial cytosolic and mitochondrial CK activities caused by infection, and also inhibited the reduction of branchial ATP levels. Supplementation with 100, 200 and 300 mg thymol/kg prevented the inhibition of branchial AK and PK activities induced by aeromonosis. Supplementation of 100 mg thymol/kg prevented weight loss after A. hydrophila infection. These data suggest that supplementation with 100 mg thymol/kg exerts potent bactericidal properties and augments longevity. Supplementation at all concentrations of thymol prevented A. hydrophila-induced branchial bioenergetics; nevertheless, higher concentrations were associated with side-effects.