Pseudomonas M162 confers protection against rainbow trout fry syndrome by stimulating immunity

Aims: To evaluate the antagonistic effect of Pseudomonas M162 against Flavobacterium psychrophilum. Methods and Results: The antagonistic activity of M162 was tested in vivo and in vitro, and its mode of action examined by siderophore production and immunological responses of rainbow trout (Oncorhynchus mykiss) fry. Pseudomonas M162 inhibited the growth of Fl. psychrophilum in vitro and increased the resistance of the fish against the pathogen, resulting in a relative per cent survival (RPS) of 39·2%. However, the siderophores produced by M162 did not have an inhibitory effect on Fl. psychrophilum. In fish fed with M162, the probiotic colonized the gastrointestinal tract and stimulated peripheral blood leucocyte counts, serum lysozyme activity and total serum immunoglobulin levels after 3 weeks from the start of feeding. Conclusions: This study showed the potential of Pseudomonas M162 as a probiotic by reducing the mortalities that occurred during an experimental Fl. psychrophilum infection, resulting mainly through the immunostimulatory effects of the bacterium. Significance and Impact of the Study: Rainbow trout fry syndrome (RTFS) causes high mortalities during the early life stages of the fish’s life cycle, partly because their adaptive immunity has not yet fully developed. Thus, immunomodulation by probiotics could be an effective prophylactic method against RTFS.     

Entericidin Is Required for a Probiotic Treatment (Enterobacter sp. Strain C6-6) To Protect Trout from Cold-Water Disease Challenge

Flavobacterium psychrophilum causes bacterial cold-water disease in multiple fish species, including salmonids. An autochthonous Enterobacter strain (C6-6) inhibits the in vitro growth of F. psychrophilum, and when ingested as a putative probiotic, it provides protection against injection challenge with F. psychrophilum in rainbow trout. In this study, low-molecular-mass (≤3 kDa) fractions from both Enterobacter C6-6 and Escherichia coli K-12 culture supernatants inhibited the growth of F. psychrophilum. The ≤3-kDa fraction from Enterobacter C6-6 was analyzed by SDS-PAGE, and subsequent tandem mass spectroscopy identified EcnB, which is a small membrane lipoprotein that is a putative pore-forming toxin. Agar plate diffusion assays demonstrated that ecnAB knockout strains of both Enterobacter C6-6 and E. coli K-12 no longer inhibited F. psychrophilum (P < 0.001), while ecnAB-complemented knockout strains recovered the inhibitory phenotype (P < 0.001). In fish experiments, the engineered strains (C6-6 ΔecnAB and C6-6 ΔecnAB<pET101::ecnAB>) and the wild-type strain (C6-6) were added to the fish diet every day for 38 days. On day 11, the fish were challenged by injection with a virulent strain of F. psychrophilum (CSF 259-93). Fish that were fed C6-6 had significantly longer survival than fish fed the ecnAB knockout strain (P < 0.0001), while fish fed the complemented knockout strain recovered the probiotic phenotype (P = 0.61). This entericidin is responsible for the probiotic activity of Enterobacter C6-6, and it may present new opportunities for therapeutic and prophylactic treatments against similarly susceptible pathogens.     

Antagonistic activity of two potential probiotic bacteria from fish intestines and investigation of their effects on growth performance and immune response in rainbow trout (Oncorhynchus mykiss)

The probiotic activity of two bacterial strains, Lactobacillus casei and Lactobacillus plantarum, isolated from common carp intestines was studied using antagonistic tests in vitro against Yersinia ruckeri. Randomly assigned to triplicate groups were 450 rainbow trout (mean weight, 20 ± 3 g) fed three different diets: a commercial feed, or the same feed incorporated into either 5 × 10⁷ CFU g^?1 of L. casei or L. plantarum. After a 30‐day feeding trial, 30 fish in each group were challenged with Yersinia ruckeri by intraperitoneal injection. Growth parameters were significantly increased in both treatment groups. Immune parameters such as lysozyme activity, alternative complement activity and total immunoglobulin level were significantly higher in the L. casei group than in fish fed the control diet, while no significant differences were revealed between the L. plantarum and control groups. Mortality rates of fish fed L. casei and L. plantarum were lower than in fish fed the control diet after challenging with Y. ruckeri.     

Influence of a combination of two potential probiotic strains, Lactobacillus rhamnosus IMC 501® and Lactobacillus paracasei IMC 502® on bowel habits of healthy adults

Aims: This study aims to investigate the effect of different kinds of food products enriched with a combination of two potential probiotic strains, Lactobacillus rhamnosus IMC 501^® and Lactobacillus paracasei IMC 502^®, on bowel habits of healthy adults. Methods and Results: Fifty healthy volunteers took part in a double‐blind placebo probiotic feeding study (25 fed probiotics, 25 fed placebo) for 12 weeks. Each volunteer ingested daily one or more food products enriched with a combination of the two potential probiotic strains (probiotic group) or the same food products without the probiotics (control group). Faecal samples were collected before, at the end and 2 weeks later the intervention period, and some of the main groups of faecal bacteria were enumerated by plate count and real‐time PCR. Questionnaires on bowel habits were submitted to volunteers. After the intervention, a significant increase in faecal lactobacilli and bifidobacteria were observed in the probiotic group, and stool frequency and stool volume were higher in the probiotic group than in the placebo group. Conclusions: Daily consumption of food products enriched with the two potential probiotic strains, Lact. rhamnosus IMC 501^® and Lact. paracasei IMC 502^®, contributes to improve intestinal microbiota with beneficial properties and enhances bowel habits of healthy adults. Significance and Impact of the Study: The study revealed that Lact. rhamnosus IMC 501^® and Lact. paracasei IMC 502^® exert a positive effect, in terms of improved bowel habits, on healthy adults.     

Coriolus versicolor polysaccharides enhance the immune response of crucian carp (Corassius auratus gibelio) and protect against Aeromonas hydrophila

To investigate the effect of Coriolus versicolor polysaccharides (CVPS) on the immune response of crucian carp (Corassius auratus gibelio), fish were fed diets containing CVPS at different concentrations including 0.5, 1.0 and 2.0 g kg^?1 for 5 weeks. Other groups of fish were vaccinated by intraperitoneal injection (i.p.) against Aeromonas hydrophila with a killed bacterin at the beginning of the experiment and fed the same diets as described above. Additionally, control fish and vaccinated‐only fish were fed basal diets without CVPS supplementation. The phagocytosis, lysozyme activity, complement components C3 and C4, E‐C3bRR (Erythrocyte‐C3b rosette rate) and E‐CIRR (Erythrocyte‐immune complex rosette rate) levels and circulating antibody titers in the serum were monitored. Five weeks after feeding the prescribed diet, fish were challenged with A. hydrophila and the mortalities recorded. Results showed that feeding non‐vaccinated and vaccinated crucian carp with CVPS stimulated the phagocytosis of leukocytes, lysozyme, complement components C3 and C4, erythrocyte immune adherence, and circulatory antibody titers in serum in vaccinated crucian carp. Immune parameters increased to their highest levels after 3 weeks of feeding the diet containing 0.5 or 1.0 g kg^?1 CVPS. These doses also resulted in the highest protection in the challenge experiment. Best survival (85%) was in the vaccinated group fed the diet containing 1.0 g kg^?1 CVPS, whereas almost 80% of control fish (negative control) and 50% of vaccinated‐only fish (positive control) died.     

Isolation and characterization of new potential probiotic bacteria based on quorum-sensing system

Aims: This work was aimed at identifying strains which can degrade quorum‐sensing (QS) molecules from fish gut, with properties suitable for use as probiotic in aquaculture. Methods and Results: A total of 200 strains were obtained from the intestine gut of Carassius auratus gibelio after enrichment in KG medium contained 500 μg l^?1 of C6‐HSL as the sole source of carbon and nitrogen; one strain named QS inhibitor (QSI)‐1 was identified as the genus Bacillus spp. by morphological phenotypes, and the strain also possessed an aiiA homologue gene using PCR amplification. In vitro, QSI‐1 strongly interfered with violacein production by Chromobacterium violaceum. Coculture of QSI‐1 with fish pathogen effectively reduced the amount of acyl‐homoserine lactones (AHLs) and the extracellular proteases activity of Aeromonas hydrophila YJ‐1. The oral LD50 of QSI‐1 to fish was more than 10¹¹ CFU shown that it was avirulent to fish. Fish fed diet supplemented with QSI‐1 had good survival, suggesting that QSI‐1 showed protection against Aer. hydrophila infection. Conclusions: The results indicate that the isolate QSI‐1 might have the potential possibility to be used as a probiotic in aquaculture. Significance and Impact of the Study: This is the first report to describe a bacterium isolated from the intestine gut of C. auratus gibelio which can degrade AHLs and has the probiotic characteristics for its use in aquaculture.     

Effects of dietary probiotic supplementations on prevention/treatment of yersiniosis disease

Aims:  To evaluate Enterobacter cloacae and Bacillus mojavensis , isolated from rainbow trout gut in the present study, as a probiotic to control yersiniosis disease.
Methods and Results:  A strain of Ent. cloacae and B. mojavensis , isolated from the digestive tract of rainbow trout had an antagonistic effect to Yersinia ruckeri , which causes yersiniosis. After feeding fish with 1 × 10⁸ cells g⁻¹ probiotic containing feed for 60 days, the fish survival rate increased to 99·2% following challenge with Y. ruckeri compared with controls that had 35% survival rate. Effects of Ent. cloacae and B. mojavensis on weight gains and stimulation of red blood cells, white blood cells, platelets and hemoglobin were also evaluated in separate groups of fish fed probiotic containing feed for 2 months. Probiotic significantly affected white blood cells, hemoglobin and weight gains of the experimental fish.
Conclusions:  Enterobacter cloacae and B. mojavensis , can be used to prevent and control yersiniosis disease.
Significance and Impact of the Study:  In conclusion, concomitant use of Ent. cloacae and B. mojavensis as a feed supplement is beneficial to rainbow trout. Use of these organisms can protect fish from yersiniosis and enhance digestibility and utilization of feed. Use of such probiotics may also limit the use of antibiotics and other chemicals in control and treatment of diseases, and thus contribute to the effort to reduce environmental contamination by residual antibiotics and chemicals .     

Influence of feeding the leucine metabolite β-hydroxy-β-methylbutyrate (HMB) on the non-specific cellular and humoral defence mechanisms of rainbow trout (Oncorhynchus mykiss)

Previous studies have shown that leucine metabolite β‐hydroxy‐β‐methylbutyrate (HMB) increases the immune function in animals as measured by cellular and humoral immune responses. In the present study the influence of feeding HMB on the nonspecific cellular and humoral defence mechanisms and protection against furunculosis in rainbow trout (Oncorhynchus mykiss) was examined. HMB was fed in a pelleted ration at either 0 (control), 10, 25 or 50 mg  kg^?1 bw day^?1 for 8 weeks. Blood and pronephros cells were taken at random from 10 fish in each group for the analyses. The respiratory burst activity (RBA) and potential killing activity (PKA) of phagocytes, lymphocyte proliferation stimulated by either concanavalin (ConA) or lipopolysaccharide (LPS), lysozyme activities and total immunoglobulin (Ig) levels in plasma were analysed at 0, 1, 2, 3, 4, 6 and 8 weeks. After 4 weeks of feeding HMB, a challenge test was performed by injection of Aeromonas salmonicida into the fish. HMB approximately doubled the respiratory burst activity and potential killing activity ability of polymorphonuclear (PMN) and morphonuclear (MN) cells (P < 0.01) and increased the mitogen‐stimulated lymphocyte proliferation (P < 0.01) when compared with the control group. HMB feeding also increased (P < 0.01) the lysozyme activity in plasma and total Ig levels in serum. During the 14‐day challenge test, mortality was decreased (P < 0.01) by up to 62% in HMB‐fed fish compared with the control group mortality. In conclusion, the non‐specific immune enhancement by HMB resulted in protection against furunculosis in the rainbow trout.     

Effects of Lactobacillus rhamnosus ATCC 7469 on Different Parameters Related to Health Status of Rainbow Trout (Oncorhynchus mykiss) and the Protection Against Yersinia ruckeri

In the current study, we investigated the effect of a probiotic bacterium (Lactobacillus rhamnosus ATCC 7469) microencapsulated with alginate and hi-maize starch and coated with chitosan on improving growth factors, body composition, blood chemistry, and the immune response of rainbow trout (initial weight: 18.41 ± 0.32 g). Four experimental diets were formulated to feed fish for 60 days. They were control diet without any additive (C), diet added with beads without probiotic (E), a probiotic sprayed to the diet (L.r), and encapsulated probiotic supplemented diet (E-L.r). The results indicated that feeding with E-Lr significantly improved weight gain (84.98 g) and feed conversion ratio (0.95) compared to the other groups (P < 0.05). Also, fish fed E-Lr diet had a significantly higher value of whole-body protein (17.51%), total protein in the blood (4.98 g/dL), lysozyme (30.66 U/mL), alternative complement pathway hemolytic activity (134 U/mL), superoxide dismutase (203 U/mg protein), and catalase (528.33 U/mg protein) (P < 0.05) as compared to those fed the control diet. Similarly, a higher relative expression of immune-related genes such as interleukin-1 (Il-1) and tumor necrosis factor-alpha (TNF-1α) were reported in those fed E-L.r and L.r diets respectively. Interestingly, the fish fed dietary E-L.r had a significantly lower value of lipid in the whole body (4.82%) and cholesterol in the blood (160.67%) in comparison with those fed the control diet (P < 0.05). At the end of the experiment, all groups were challenged by Yersinia ruckeri where the survival rate of rainbow trout fed dietary E-L.r (70.36%) was statistically higher than that of the others (P < 0.05). Overall, the results suggested that encapsulated probiotic Lact. rhamnosus ATCC 7469 acted better than unencapsulated probiotic and has a potential to improve growth performance, flesh quality, and the immune response of rainbow trout.

     

Effect of probiotic Bacillus subtilis Ch9 for grass carp,Ctenopharyngodon idella (Valenciennes, 1844), on growth performance,digestive enzyme activities and intestinal microflora

In the present study, Bacillus subtilis Ch9 was evaluated as a probiotic in grass carp, Ctenopharyngodon idella (Valenciennes, 1844). For 56 days the grass carp (50 ± 2.5 g) were given a feed containing B. subtilis Ch9 in three concentrations: 1.0 × 10⁹ (T₁), 3.0 × 10⁹ (T₂) and 5.0 × 10⁹ (T₃) CFU kg^?1 feed in triplicate treatments. The control group (T₀) was given feed without B. subtilis Ch9 for the same period. Determined were the specific growth rate (SGR), feed conversion ratio (FCR), and digestive enzyme activities in the intestine and hepatopancreas as well as the intestinal microflora. After 56 days, fish receiving the diets supplemented with B. subtilis Ch9 showed significantly higher SGR and lower FCR (P < 0.05) than those fed the control diet. There was no significant different in SGR and FCR among T₁, T₂ and T₃ nor was the survival rate affected (P > 0.05) by the dietary treatments. From days 14 to 56 of the experiment, higher protease, amylase and lipase activities in the foregut, midgut hindgut and hepatopancreas were observed in T₁, T₂ and T₃ (P < 0.05) compared with the control over a short‐term (14–28 days). Enzyme activity did not increase after long‐term feeding with B. subtilis Ch9 (56 days), but was still higher than that of control fish (P < 0.05). Fish fed the probiotic had an increase in trend of total aerobic and facultative anaerobic bacterial quantity (P > 0.05), but the ratio of Bacillus was significantly higher (P < 0.05) than in control fish. The total anaerobic bacterial quantity, Bifidobacterium and Lactobacillus were significantly higher (P < 0.05) in fish fed B. subtilis Ch9 compared with fish fed control feed. In conclusion, an optimum dose of B. subtilis Ch9 could modulate intestinal microflora, induce digestive enzyme activity and potentially promote the digestion and absorption of nutrients, as well as improve the growth performance of grass carp significantly.     

Dietary Administration of Probiotic Aeromonas veronii V03 on the Modulation of Innate Immunity,Expression of Immune-Related Genes and Disease Resistance Against Aeromonas hydrophila Infection in Common Carp (Cyprinus carpio)

This study investigates the effects of dietary Aeromonas veronii V03 supplementation on growth performances, innate immunity, and expression of immune-related genes in lymphoid organs of Cyprinus carpio and resistance to Aeromonas hydrophila infection. Fish were fed for 4 weeks with basal diet (BD; without probiotic), and experiment diet containing different doses of A. veronii V03 at 3.2 × 10⁷ (DI) and 3.5 × 10⁹ (DII) CFU g⁻¹ of diet. At the end of the probiotic feeding trial, fish were challenged with A. hydrophila, and the percentage of survival rates was recorded over 7 days. Results revealed that fish fed with A. veronii V03 demonstrated a significant improvement in growth and enhancement of innate immunity, including respiratory burst, myeloperoxidase, and lysozyme activities, and total immunoglobulin level compared with BD fed to fish. Relatively, expression of cytokines (MyD88, IL-1β1, IL-8, and IL-10) and c- and g-type lysozymes were significantly up- and downregulated in lymphoid organs of fish. Moreover, dietary supplementation of A. veronii V03 exhibited significantly (p < 0.001) higher survival rates of DI (90%) and DII (96.66%) compared with BD (53.33%) fed fish against A. hydrophila infection. These findings help to understand the effects of probiotic A. veronii V03 administrated feed influences on growth and ailment resistance to A. hydrophila infection by regulating innate and systemic immunity in common carp fish.

     

Combined and Singular Effects of Dietary PrimaLac® and Potassium Diformate (KDF) on Growth Performance and Some Physiological Parameters of Rainbow Trout (Oncorhynchus mykiss)

The present study was conducted to assess the effects of combined and singular dietary administration of PrimaLac® and potassium diformate (KDF) on growth performance, feed utilization, digestive enzymes activity, and some physiological parameters of rainbow trout (Oncorhynchus mykiss) juvenile. Three hundred sixty rainbow trout juveniles (25 ± 1.8 g) were randomly stocked in 300-L tanks (30 fish/tank), and fed three times daily on a basal diet (control), diets incorporated with 12 g kg⁻¹ KDF (FT₁), 1.5 g kg⁻¹ PrimaLac® (FT₂), and combination of 1.5 g kg⁻¹ probiotic and 12 g kg⁻¹ KDF (FT₃) in triplicates, for 8 weeks. At the end of feeding trial, growth performance, body composition, digestive enzymes, liver enzymes, and biochemical parameters were measured. Our results revealed that combined administration of PrimaLac® and KDF (FT₃) exhibited significantly higher weight gain and specific growth rate (SGR) compared to other groups (P < 0.05). Glucose and cortisol levels showed no significant differences between fish fed different test diets (P > 0.05). The highest lipase, protease and amylase activity were observed in group of fish fed FT₃ followed by FT₂ and FT₁. Besides, the diets FT₂ and FT₃ led to significantly lower of ALP, ALT, and AST compared to control group. The present results indicated that combined administration of PrimaLac® and KDF can be considered as a beneficial feed additive and growth promotor for O. mykiss juvenile.

     

Influence of Tribulus terrestris extract on the survival and histopathology of Oreochromis mossambicus (Peters, 1852) fry before and after Streptococcus iniae infection

The aim of this study was to determine the effects of Tribulus terrestris extract (TT) on growth performance, disease resistance and histopathological changes in intestine and liver tissues of Oreochromis mossambicus (Peters, 1852) first‐feeding fry before and after exposure to Streptococcus iniae. Five isonitrogenous and isocaloric diets were formulated to contain 0 (control), 200, 400, 600, and 800 mg kg^?1 TT. After feeding for 45 days, fish were infected with S. iniae and mortalities recorded. Final weight, weight gain and SGR of tilapia fry fed the 400 mg kg^?1 TT diet were significantly greater than that of control diet. In the challenge experiment, the best survival rate was obtained with 400 mg kg^?1 TT supplementation. Infection by S. iniae appeared to have a negative effect on histopathological findings and outcome than did TT‐800 used alone. However, administration of TT (200 or 400 mg extract kg^?1) resulted in overall improvement in the intestine and liver histopathology, emphasizing the protective potential of TT. The present study suggests the protective potential of TT in alleviating intestinal and hepatic damage that can occur after a S. iniae infection. It was concluded that 400 mg kg^?1 TT can enhance growth and disease resistance during first–feeding of O. mossambicus fry. This suggests that TT may be an alternative to antibiotics in controlling streptococcal disease in tilapia culture.     

Effects of dietary xanthophylls/astaxanthin ratios on the growth and skin pigmentation of large yellow croaker Larimichthys crocea (Richardson, 1846)

An 8‐week feeding trial was conducted to evaluate the effects of dietary xanthophylls/ astaxanthin ratio on the growth and skin color of large yellow croaker, Larimichthys crocea. Five pigment‐supplemented diets were formulated to contain 75/0, 50/25, 37.5/37.5, 25/50 and 0/75 mg kg^?1 of xanthophylls/astaxanthin. The xanthophylls contain 89.31% lutein and 6.12% zeaxanthin. A diet without pigment supplementation was used as the control. The large yellow croaker juveniles (13.80 ± 0.03 g) were randomly distributed in 18 sea cages (1.0 × 1.0 × 1.5 m) at a density of 45 fish per cage. Water temperature ranged from 21 to 31°C during the feeding trial. To obtain results, the survival rate, specific growth rate, feed conversion ratio, skin redness, skin yellowness, skin lightness, skin carotenoid content and skin melanin content were measured. The results showed that the survival rate, specific growth rate and feed conversion ratio were not significantly affected by dietary treatments (P > 0.05). The ventral skin lightness was also not affected by dietary treatments (P > 0.05); however, the dorsal skin lightness of fish fed with the control diet was significantly lower than those fed with pigment‐supplemented diets (P < 0.05). The lowest values of yellowness and carotenoid content both in the ventral skin and dorsal skin were found in the control group. Yellowness and carotenoid content increased with an increasing proportion of dietary xanthophylls in both the ventral and dorsal skin. Higher redness values were found in the compound pigment groups, either in the dorsal skin or ventral skin. Fish fed with the control diet showed a higher melanin content in the dorsal skin than those fed with pigment‐supplemented diets, although differences were not significant (P > 0.05). Lightness and yellowness were linearly related to skin carotenoid content. Meanwhile, skin yellowness and carotenoid content were linearly related to the proportion of xanthophylls in dietary pigments.     

In vivo Testing of Functional Properties of Three Selected Probiotic Strains

Summary Lactobacillus acidophilus M92, Lactobacillus plantarum L4 and Enterococcus faecium L3 were previously selected as probiotic strains on the base of in vitro selection criteria. To investigate functional properties of these three probiotic strains in vivo, Swiss albino mice were used as animal model. Survival, competition, adhesion and colonization were monitored in the gastrointestinal tract, as well as the immunomodulating capability of L. acidophilus M92, L. plantarum L4 and E. faecium L3. During the feeding of mice with probiotic strains with daily dose of 2 × 10¹⁰ rifampicin-resistant cells, the number of lactic acid bacteria in the faeces increased and reduction of enterobacteria and sulphite-reducing clostridia was observed. Rifampicin-resistant colonies of probiotic strains could be reisolated from the faeces of mice fed with the rifampicin-resistant cells. The similar results were obtained in homogenates of small and large intestine of mice on the first and fourteenth days after feeding with L. acidophilus M92, L. plantarum L4 and E. faecium L3. The adherence of the probiotic strains obtained in vitro correlated with their capability to adhere to mouse ileal epithelial cells in vivo. After oral immunization of mice with viable cells of L. acidophilus M92, L. plantarum L4 and E. faecium L3 with a daily dose of 2 × 10¹⁰ cells, the concentrations of serum IgA, IgG and IgM antibodies from all groups of mice were significantly higher in comparison to the control.     

CONDITIONAL PRODUCTION OF A FUNCTIONAL FISH GROWTH HORMONE IN THE TRANSGENIC LINE OF NANNOCHLOROPSIS OCULATA (EUSTIGMATOPHYCEAE)1

Plasmid phr‐YPGHc, containing the fish growth hormone (GH) cDNA driven by a heat shock protein 70A promoter and a RUBISCO SSU 2 promoter, was transferred into the protoplast of marine microalga Nannochloropsis oculata (Droop) D. J. Hibberd by electroporation. Four transgenic clones were obtained in which the transferred phr‐YPGHc was integrated into the genome and existed stably at least until the 50th generation. When we treated these transgenic microalgae by heat shock, the heterologous fish GH was produced in the amount of 0.42 to 0.27 μg · mL^?1 from the 50 mL of medium. We incubated artemia with the wildtype and transgenic N. oculata for 6 h and then fed these microalgae‐treated artemia to red‐tilapia larvae. After feeding, the growth of larvae that were fed artemia incubated with transgenic microalgae was greater (i.e., statistically significant: P < 0.05) than that of larvae that were fed artemia incubated with nontransgenic microalgae: 316% versus 104% in weight gain, and 217% versus 146% in body length increase, respectively. Therefore, the N. oculata enables production of functional GH, and we propose that it might be an excellent bioreactor material.     

Hilyses®, fermented Saccharomyces cerevisiae, enhances the growth performance and skin non-specific immune parameters in rainbow trout (Oncorhynchus mykiss)

Effects of Hilyses^®, fermented Saccharomyces cerevisiae (S. cerevisiae), on growth, body composition and skin mucus immune components in rainbow trout were quantified. Ninety rainbow trout (105 ± 5 g) were randomly assigned to 2 groups in triplicates and fed dietary Hilyses^® (5 g kg^?1) or control diet without Hilyses^® for 50 days. Results of this study demonstrated that growth performance increased significantly by the dietary yeast supplement; however body composition was not affected in treatment group. At the 45th and 50th day of feeding trial, results of mucus samples demonstrated that yeast supplementation in treatment group significantly promoted enzyme activities, namely lysozyme, protease, alkaline phosphatase and esterase compared to control group. Significant increases were also observed in hemagglutination and antibacterial activity against Yersinia ruckeri in fish fed treatment diet. The present study suggests that fermented S. cerevisiae may effectively promote the growth performance and skin non-specific immune parameters in rainbow trout.     

Partial Evaluation of Autochthonous Probiotic Potential of the Gut Microbiota of Seriola lalandi

Seriola lalandi is an economically important species that is globally distributed in temperate and subtropical marine waters. Aquaculture production of this species has had problems associated with intensive fish farming, such as disease outbreaks or nutritional deficiencies causing high mortality. Intestinal microbiota are involved in many processes that benefit a host, such as disease control, stimulation of the immune response, and the promotion of nutrient metabolism. The aim of this study is to evaluate the in vitro probiotic properties of bacteria isolated from the intestinal content of wild Seriola lalandi. The probiotic potential was evaluated in terms of (i) the antimicrobial activity against vibrios causing outbreaks in farmed fish; (ii) the ability to stimulate genes related to an innate immune response in fish; and (iii) antibiotic resistance. Nineteen isolates identified as Pseudomonas, Shewanella, Psychrobacter, and Acinetobacter showed antimicrobial activity and significant relative expression of cytokines, serum amyloid A protein (SAA), hepcidin, and lysozyme. A positive correlation was observed between the levels of expression and the bacterial load after 24 h of exposure. Pseudomonas isolates showed a level of antibiotic resistance. In conclusion, isolates of the genera Shewanella, Psychrobacter, and Acinetobacter could serve as potential probiotics in S. lalandi culture.

     

Investigation of the impact of feeding Lactobacillus plantarum CRL 1815 encapsulated in microbially derived polymers on the rat faecal microbiota

Aims

The aim of this study was to evaluate the impact of the administration of microencapsulated Lactobacillus plantarum CRL 1815 with two combinations of microbially derived polysaccharides, xanthan : gellan gum (1%:0·75%) and jamilan : gellan gum (1%:1%), on the rat faecal microbiota.

Methods and Results

A 10‐day feeding study was performed for each polymer combination in groups of 16 rats fed either with placebo capsules, free or encapsulated Lact. plantarum or water. The composition of the faecal microbiota was analysed by fluorescence in situ hybridization and temporal temperature gradient gel electrophoresis. Degradation of placebo capsules was detected, with increased levels of polysaccharide‐degrading bacteria. Xanthan : gellan gum capsules were shown to reduce the Bifidobacterium population and increase the Clostridium histolyticum group levels, but not jamilan : gellan gum capsules. Only after administration of jamilan : gellan gum‐probiotic capsules was detected a significant increase in Lactobacillus‐Enterococcus group levels compared to controls (capsules and probiotic) as well as two bands were identified as Lact. plantarum in two profiles of ileum samples.

Conclusions

Exopolysaccharides constitute an interesting approach for colon‐targeted delivery of probiotics, where jamilan : gellan gum capsules present better biocompatibility and promising results as a probiotic carrier.

Significance and Impact of Study

This study introduces and highlights the importance of biological compatibility in the encapsulating material election, as they can modulate the gut microbiota by themselves, and the use of bacterial exopolysaccharides as a powerful source of new targeted‐delivery coating material.     

Characterization of the Properties of Human- and Dairy-Derived Probiotics for Prevention of Infectious Diseases in Fish

The present study aimed to investigate the potential probiotic properties of six lactic acid bacteria (LAB) intended for human use, Lactobacillus rhamnosus ATCC 53103, Lactobacillus casei Shirota, Lactobacillus bulgaricus, L. rhamnosus LC 705, Bifidobacterium lactis Bb12, and Lactobacillus johnsonii La1, and one for animal use, Enterococcus faecium Tehobak, for use as a fish probiotic. The strains for human use were specifically chosen since they are known to be safe for human use, which is of major importance because the fish are meant for human consumption. The selection was carried out by five different methods: mucosal adhesion, mucosal penetration, inhibition of pathogen growth and adhesion, and resistance to fish bile. The adhesion abilities of the seven LAB and three fish pathogens, Vibrio anguillarum, Aeromonas salmonicida, and Flavobacterium psychrophilum, were determined to mucus from five different sites on the surface or in the gut of rainbow trout. Five of the tested LAB strains showed considerable adhesion to different fish mucus types (14 to 26% of the added bacteria). Despite their adhesive character, the LAB strains were not able to inhibit the mucus binding of A. salmonicida. Coculture experiments showed significant inhibition of growth of A. salmonicida, which was mediated by competition for nutrients rather than secretion of inhibitory substances by the probiotic bacteria as measured in spent culture liquid. All LAB except L. casei Shirota showed tolerance against fish bile. L. rhamnosus ATCC 53103 and L. bulgaricus were found to penetrate fish mucus better than other probiotic bacteria. Based on bile resistance, mucus adhesion, mucus penetration, and suppression of fish pathogen growth, L. rhamnosus ATCC 53103 and L. bulgaricus can be considered for future in vivo challenge studies in fish as a novel and safe treatment in aquaculture.