In vitro antagonistic effect and in vivo protective efficacy of Gram-positive probiotics versus Gram-negative bacterial pathogens in finfish and shellfish

It is well established that Gram-positive probiotic bacteria are efficacious as a preventive tool for control of disease outbreaks in aquaculture. Secretion of bioactive compounds such as bacteriocins, siderophores, enzymes, and antibiotics by Gram-positive probiotics can adversely affect potential pathogenic of Gram-negative bacteria in the intestine of aquatic animals providing a barrier against attachment and colonization of disease agents in the gastrointestinal (GI) tract. More than 50 species of Gram-positive bacteria [mostly Bacillus and lactic acid bacteria (LAB)], originally isolated from GI tract of aquatic animals have been examined as potential probiotics in about 40 commercial finfish and shellfish species. These putative probiotics are thought to interact with or antagonize Gram negative pathogens in the GI tract. Members of genera Vibrio and Aeromonas are the most important pathogens of aquatic animals, and Gram-positive probiotics can inhibit their growth in vitro. There are, however, minimum data showing minimum inhibitory concentration of Gram-positive probiotics against these pathogenic Gram-negatives. Moreover, incorporation of Gram-positive probiotics into aquafeeds can also improve host immune-physiological functions and enhance disease resistance. There are, however, a lack of knowledge correlating the in vitro antagonist data with the in vivo protective efficacies of selected Gram-positive probiotics. The probiotic dosage optimization is, therefore missed in the most studied works. In addition, scarce data are available to demonstrate behavioral growth of Gram-positive probiotics such as synergistic or antagonistic effects. The present review addressed in vitro antagonistic effects and in vivo clinical efficacy of putative Gram-positive probiotics administration versus Gram-negative pathogens in finfish and shellfish and discussed the current gaps and future research works required

Medicinal Herbs and Plants: Potential Treatment of Monogenean Infections in Fish

Monogenean parasites are responsible for tremendous annual economic losses in both freshwater and marine aquaculture operations. These losses have led to the extensive deployment of chemical treatments, such as praziquantel and mebendazole, in an effort to manage infections from these parasites. While effective, the environmental side effects associated with these treatments are, however, concerning. In recent years, medicinal plants including rosemary (Rosmarinus officinalis), garlic (Allium sativum), ginger (Zingiber officinale), ashanti pepper (Piper guineense), peppermint (Mentha piperita), tea tree (Melaleuca alternifolia), bge seeds (Semen aesculin), and bupleurum chinense roots (Bupleuri chinensis) have demonstrated promising anthelmintic activity against monogenean infections in fish. Most of these plants have been applied to infected host as part of a bath treatment regime, with less attention being paid to their application as an oral treatment. There is also limited information on the bioavailability of compounds present in these natural remedies, into fish organs. As the majority of the aforementioned plants have some immunostimulatory effects on fish, many of these studies have examined the herbs potency on fish immune-physiological variables. In addition, the number of fish species involved with in vivo trials where anthelmintic activity or toxicity was examined is minimal, and most of the studies focused on only one species of fish. This review focuses the evidence for anthelmintic activity of medicinal plants in fish and discuss the gaps where further research is required

Effects of Apple (Malus pomila) Pomace-Derived Pectin on the Innate Immune Responses, Expressions of Key Immune-Related Genes, Growth Performance, and Digestive Enzyme Activity of Rainbow Trout (Oncorhynchus mykiss)

Pectins are a group of carbohydrates found in structural parts of terrestrial plants with wide industrial and biomedical applications. This study was designed to investigate the dietary effects of apple pomace-derived pectin (APDP) in rainbow trout (Oncorhynchus mykiss). Four formulated diets were provided with different inclusion levels of APDP for 30 days: 0, 5, 10, and 20 g kg−1; referred to as control, P1, P2, and P3, respectively. In this study, 300 fish (3.56 ± 0.007 g) were randomly distributed into twelve fiberglass tanks and fed 3% of their respective body weight four times a day. At the end of the experiment, growth parameters, including weight gain, specific growth rate, and food conversion ratio (FCR) were significantly improved in P1 and P2 treatments compared to those of the other treatments. Results from proximate composition analysis showed that protein content increased, and lipid decreased in the P2 and P3 groups. Serum lysozyme, complement activity, total immunoglobulin levels, and total protein were significantly enhanced in all treatments compared to those of the control group. Gene expression results showed no significant difference in regulation of interleukin-1β (IL-1β); however, up-regulation of lysozyme, interleukin-8 (IL-8), and tumor necrosis factor-α (TNF-α) was observed in both P1 and P2. Unlike lipase, the activity of protease and amylase significantly increased in fish receiving different levels of APDP compared to the control (p < 0.05). In conclusion, the present findings suggest APDA as a promising feed additive for rainbow trout

Effects of dietary monoterpene, myrcene, administration on immune- and health-related genes expression in common carp gill following exposure to copper sulfate

The present study assessed the potential benefits of myrcene administration to suppress negative effects of copper exposure on immune-, antioxidant-, tight junction-, stress- and osmoregulatory-related gene expressions in common carp (Cyprinus carpio) gill. Fish were fed with diets containing 0 (control), 0.5 (M0.5) and 1 (M1) myrcene for 6 weeks, and then, exposed to 0.25 mg/L copper for further two weeks. The fish gill samples were taken for gene expression assays after six and eight weeks. The results showed that there were interaction effects of myrcene levels and copper exposure on superoxide dismutase (sod), catalase (cat), glutathione peroxidase (gpx), glutathione-s-transferase (gst), glutathione reductase (gr), heat shock protein-70 (hsp70), interleukin 1-beta (il1b), interleukin 10 (il10), tumor necrosis factor-alpha (tnfa), occludin (occl), caludin 3 (cld3), caludin 7 (cld7), and Na+-K+-ATPase (nka) genes expressions. Overall, the M0.5 treatment had significantly lower antioxidant genes expression, and higher hsp70, cytokines, tight-junction proteins, and nka genes expression, compared to the control treatment, before copper exposure. Copper exposure significantly down-regulated most of the tested genes (except il10), however, the M0.5 treatment had significantly higher antioxidant (except gpx), hsp70, cld7, and nka gene expression compared to the control treatment. The M1 treatment showed fluctuated antioxidant gene expressions, down-regulated gene expression of the pro-inflammatory cytokines, and occl, and up-regulation of cld3 gene expressions, before copper exposure. After copper exposure, this treatment had significantly higher gr and cat expression compared to the control; moreover, there was a marked up-regulation in il10 gene expression in this treatment, which was the highest value among all treatment combinations. In conclusion, copper exposure significantly down-regulates antioxidant-, inflammatory-, and tight junction-related along with hsp70 and nka genes expression in common carp gills. Pre-treatment with 0.5 myrcene is beneficial to suppress such negative effects, probably due to its antioxidant properties. However, myrcene administration must be done with caution, as higher levels may interfere with antioxidant and immune defenses. © 2020 Elsevier Lt

Effects of elephant's foot (Elephantopus scaber) extract on growth performance, immune response, and disease resistance of nile tilapia (Oreochromis niloticus) fingerlings

Medicinal plant has been applied as an alternative strategy for antibiotics and chemotherapeutics for controlling the outbreak of diseases in tilapia farming. In this study, five doses of Elephantopus scaber extract (ESE) were added to the basal diet at 0, 2.5, 5, 10, and 20 g kg−1 feed of Nile tilapia fingerlings (13.92 ± 0.06 g initial weight) in triplicate. After 4- and 8- weeks post-feeding, fish were sampled to determine the effects of the ESE supplemented on fish's growth performance, humoral, and skin mucus immune response. After 8 weeks post-feeding, a challenge test against Streptococcus agalactiae was carried out using 10 fish from each tank. Fish fed ESE showed significantly increased serum lysozyme (SL), serum peroxidase (SP), alternative complement (ACH50), phagocytosis (PI), and respiratory burst (RB) compared to the control group (P < 0.05). The skin mucus lysozyme (SMLA) and skin peroxidase (SMPA) were stimulated in fish fed ESE diets. Dietary inclusion of ESE significantly (P < 0.05) promoted final body weight (FW), weight gain (WG), and specific growth rate (SGR); while a reduction in feed conversion ratio (FCR) was observed in fish fed 5 g kg−1 ESE, after 8 weeks post-feeding. The challenge study indicated that the relative percent survival (RSP) was 38.10%, 76.19%, 66.67%, and 47.62% in Diet 2, Diet 3, Diet 4, and Diet 5, respectively. Among the supplemented groups, dietary of 5 g kg−1 ESE showed significantly higher RPS and the highest resistance to S. agalactiae in comparison with other groups. In conclusion, supplementation of ESE (5 g kg−1) enhanced the humoral and mucosal immunity, promoted growth performance, and improved disease resistance of Nile tilapia against Streptococcus agalactiae

Dietary supplementation of lemon verbena (Aloysia citrodora) improved immunity, immune-related genes expression and antioxidant enzymes in rainbow trout (Oncorrhyncus mykiss)

The use of veterinary drugs for the treatments of fish diseases has often health and environmental side effects and thus alternative more sustainable strategies are needed. In this study we have explored the effect of dietary administration of lemon verbena (Aloysia citrodora) leaves powder on growth, immune parameters and antioxidant enzyme activity of rainbow trout (Oncorrhyncus myskiss). The results show that adding lemon verbena (LV) leaves powder (0.5, 1 and 2), as feed supplement does not affect significantly rainbow trout growth, but increases the levels of some immune parameters. All enriched-diets induced an increase in the levels of lysozyme activity and total immunoglobulin in rainbow trout serum (P < 0.05), whilst 1 and 2 enriched-diets increased lysozyme and immunoglobulin in skin mucus. Expression of interleukin-1β (IL-1β) was enhanced in all fish supplemented with LV leaves powder (0.5, 1 and 2) whilst only the diet with the highest dose (2) induced a significantly higher expression of IL-8 and tumour necrosis factor (TNF-α). Fish fed with LV leaves powder at 1 and 2 had significantly lower expression of transforming growth factor (TGF-β, P < 0.05). Furthermore, all enriched-diets significantly increased the activity of super oxide dismutase (SOD, P < 0.05) and diets containing 1 and 2 of LV leaves powder also increased activity of glutathione-S-transferase (GST) and glutathione peroxidase (GPx). In conclusion, LV leaves powder administered as feed supplement at 2 enhances the expression of some immune-related genes (IL-1β, IL-8 and TNF- α), rises the levels of lysozyme and total immunoglobulin in serum and skin mucus and increases the activity of antioxidant enzymes (SOD, GST and GPx) in rainbow trout. © 2020 Elsevier Lt

Dietary supplementation of lemon verbena (Aloysia citrodora) improved immunity, immune-related genes expression and antioxidant enzymes in rainbow trout (Oncorrhyncus mykiss)

The use of veterinary drugs for the treatments of fish diseases has often health and environmental side effects and thus alternative more sustainable strategies are needed. In this study we have explored the effect of dietary administration of lemon verbena (Aloysia citrodora) leaves powder on growth, immune parameters and antioxidant enzyme activity of rainbow trout (Oncorrhyncus myskiss). The results show that adding lemon verbena (LV) leaves powder (0.5, 1 and 2%), as feed supplement does not affect significantly rainbow trout growth, but increases the levels of some immune parameters. All enriched-diets induced an increase in the levels of lysozyme activity and total immunoglobulin in rainbow trout serum (P < 0.05), whilst 1 and 2% enriched-diets increased lysozyme and immunoglobulin in skin mucus. Expression of interleukin-1β (IL-1β) was enhanced in all fish supplemented with LV leaves powder (0.5, 1 and 2%) whilst only the diet with the highest dose (2%) induced a significantly higher expression of IL-8 and tumour necrosis factor (TNF-α). Fish fed with LV leaves powder at 1 and 2% had significantly lower expression of transforming growth factor (TGF-β, P < 0.05). Furthermore, all enriched-diets significantly increased the activity of super oxide dismutase (SOD, P < 0.05) and diets containing 1 and 2% of LV leaves powder also increased activity of glutathione-S-transferase (GST) and glutathione peroxidase (GPx). In conclusion, LV leaves powder administered as feed supplement at 2% enhances the expression of some immune-related genes (IL-1β, IL-8 and TNF- α), rises the levels of lysozyme and total immunoglobulin in serum and skin mucus and increases the activity of antioxidant enzymes (SOD, GST and GPx) in rainbow trout. © 2020 Elsevier Lt

Removal of Congo red and malachite green from aqueous solution using heterogeneous Ag/ZnCo-ZIF catalyst in the presence of hydrogen peroxide

The bimetallic Zn/Co zeolitic imidazole frameworks (ZnCo-ZIFs) were successfully synthesized by a simple solvothermal method at room temperature. Silver elements were afterward doped onto the bimetallic frameworks to form Ag/ZnCo-ZIFs via a facile impregnation method in acetone solvent. The as-synthesized material was used as a heterogeneous catalyst for the removal reaction of Congo red (CR) and malachite green (MG) in the presence of hydrogen peroxide (H2O2). Effects of catalyst dosage, H2O2 concentration, initial concentration of the contaminants, reaction temperature, and reaction time were conducted in this work. The results showed that more than 94% and 98% removal of CR and MG were, respectively, achieved within 45 and 30 min. The presence of Ag also enhanced the removal efficiency of CR and MG. The main mechanism of removal reaction of the organic contaminants could be oxidation via hydroxyl radicals. Moreover, the catalytic activity of the material remained over 90% after four recycling cycles. Due to the efficient reactivity as well as high stability, Ag/ZnCo-ZIFs can be a potential heterogeneous catalyst to remove hazardous dyes from aqueous solution