Intestinal Vibrio Research Articles

Effects of Dietary Mannan Oligosaccharides on Growth, Nonspecific Immunity and Tolerance to Salinity Stress and Streptococcus iniae Challenge in Golden Pompano, Trachinotus ovatus

The effects of dietary supplementation with mannan oligosaccharide (MOS) on growth performance, haematological parameters, abundance of intestinal Vibrio spp., immune response, and tolerance to low salinity stress and Streptococcus iniae challenge were evaluated in pompano (Trachinotus ovatus). Pompano (3.24 ± 0.45 g) were fed six diets including a basal diet as control, and the basal diets supplemented with 0.1%, 0.2%, 0.4%, 0.6%, or 0.8% MOSs for 8 weeks. The results showed that pompano fed 0.1%–0.4% MOS had significantly improved specific growth rates ( P ≤ 0.039 ). Dietary MOS did not affect the survival rate of pompano ( P = 0.192 ). WBC count was significantly higher in fish fed diets containing 0.1%–0.6% MOS. Dietary MOS increased lymphocytes count ( P ≤ 0.042 ) and reduced monocytes and basophils counts ( P ≤ 0.019 ); however, no effects were found on neutrophils and eosinophil numbers ( P ≥ 0.064 ). Intestinal Vibrio spp. counts reduced in fish fed diets containing 0.1%–0.4% MOS ( P ≤ 0.035 ). The phagocytic ratio significantly increased in pompano fed diets containing 0.1%–0.6% MOS ( P ≤ 0.015 ), while the phagocytic index and serum lysozyme activity in fish fed 0.1%–0.4% MOS were significantly higher than the control ( P ≤ 0.035 ). There were significant positive correlations between MOS levels and fish growth on days 14, 28, 42, and 56 ( P ≤ 0.049 ). In addition, dietary MOS levels were highly correlated with blood parameters, abundance of intestinal Vibrio spp., and immune responses. Optimal dietary MOS requirements for maximal growth were estimated to be 0.440% on day 21 (R2 = 0.861), 0.385% on day 28 (R2 = 0.877), 0.371% on day 42 (R2 = 0.891), and 0.365% on day 56 (R2 = 0.750), showing decreasing tendency in MOS requirement as fish size increased. Furthermore, the optimal MOS concentration for maximal immunity based on lysozyme activity was estimated to be 0.431% (R2 = 0.817) on day 56. In addition, fish fed 0.1%–0.4% MOS showed better resistance to low salinity stress and Streptococcus iniae challenges ( P ≤ 0.014 ). In conclusion, MOS supplementation effectively reduced the prevalence of intestinal Vibrio spp. and enhanced the growth, immune responses, and tolerance to low salinity stress and Streptococcus iniae in juvenile pompano.

Dietary mannan oligosaccharides elevated growth performance, gut morphology, microbiota, body composition, feed and nutrient utilisation of pompano, Trachinotus ovatus

Pompano (Trachinotus ovatus) is a highly economical aquaculture species; however, intensive aquaculture of pompano is associated with pathogen infection, environmental stress, drug and chemical use, causing reductions in growth, survival and economic losses. Mannan oligosaccharide (MOS) is a prebiotic that has been reported to boost the growth and health of many species; however, no study has examined the effects of MOS on pompano. In the present study, the effects of dietary MOS levels on growth, body composition, intestinal microbiota, feed, and nutrient utilisation in juvenile pompano were investigated over an 8-week experiment. Five diets containing five levels of MOS (0.1%, 0.2%, 0.4%, 0.6%, and 0.8%) were fed to pompano (mean weight, 5.16 g±0.05). The results indicated that pompano fed 0.1–0.40% MOS in the diet had the highest growth performance (p ≤ 0.009), but fish fed 0.6–0.8% MOS had no impact on growth (p ≥ 0.056). MOS had no effect on the survival rate of pompano (p ≥ 0.327). The gut surface area increased in fish fed 0.1–0.4% MOS (p ≥ 0.011), but not in fish fed 0.6–0.8% MOS (p ≥ 0.102). Total aerobic bacteria (TAB) increased in fish fed 0.1–0.4% MOS (p ≤ 0.017), but TAB was not affected at 0.6–0.8% MOS (p = 0.315), whereas Vibrio count and ratio of Vibrio to TAB significantly reduced in fish fed any levels of MOS (p ≤ 0.024). Feed conversion ratio (FCR) significantly reduced (p ≤ 0.019), while feed conversion efficiency (FCE) significantly increased (p ≤ 0.014), when pompano were fed a diet containing 0.1–0.4% MOS. Protein in fish increased in fish fed a diet providing 0.1–0.4% MOS (p ≤ 0.011), but when adding higher levels of MOS (0.6% and 0.8%) to the diets, the protein content in fish did not change (p ≥ 0.072). Lipid content was significantly reduced in fish fed 0.1–0.4% MOS (p ≤ 0.035), but not at higher levels of MOS (p ≥ 0.085). The protein efficiency ratio (PER), lipid efficiency ratio (LER), and lipid productive value (LPV) boosted in fish fed diet containing 0.1–0.6% MOS (p ≤ 0.029). Protein productive value (PPV) increased in fish served diet containing 0.1–0.4% (p ≤ 0.008). Those values did not change with 0.8% MOS (p ≥ 0.137). MOS levels had positive correlations with growth performance, FCE, PER, PPV, LER, LPV and TAB (r ≥ +0.481, p ≤ 0.001), while MOS levels showed negative correlations with intestinal Vibrio and FCR of pompano (r ≥ −0.562, p ≤ 0.003). The optimal levels of MOS were 0.424% for pompano's lowest FCR, while the best MOS concentration was 0.375% for pompano’s maximal growth.

Effects of dietary yeast-derived nucleotide and RNA on growth performance, survival, immune responses, and resistance to Vibrio parahaemolyticus infection in Pacific white shrimp (Litopenaeus vannamei)

Nucleotides (NT) and RNA from yeast extracts are gaining interest as high-value feed additives. The present study intended to evaluate the influences of yeast derived-NT and RNA on the growth performance, survival, immune responses, and resistance to Vibrio parahaemolyticus infection in Pacific white shrimp. In Experiment 1, postlarvae were distributed into 7 groups, corresponding to 7 experimental diets: control, NT 0.25, NT 0.50, NT 0.75, RNA 0.25, RNA 0.50, and RNA 0.75 g/kg feed. They were fed the experimental diets for 45 days. Then, their body weights, survival rates, immune parameters, and Vibrio spp. counts in the hepatopancreas and intestines were determined. In Experiment 2, the shrimp from Experiment 1 were challenged by immersion with V. parahaemolyticus at 105 CFU/mL. Each group was fed the same diet for another 10 days to assess the disease resistance performance. The results revealed that the shrimp body weights of all groups were similar suggesting that neither NT nor RNA exerts the growth-promoting effect. However, the average survival rates of the NT and RNA groups were in the range of 89–93 %, significantly higher than that of the control (83 %). These increased survivals were in line with the reduction in the hepatopancreatic and intestinal Vibrio spp. counts and the elevated immune parameters in the NT and RNA-fed shrimp. At day 10 after the bacterial challenge, the highest survival rates were observed in the RNA 0.50 and 0.75 g/kg feed groups (81 % and 82 %, respectively), followed by the RNA 0.25 (70 %) and NT 0.75 g/kg feed (68 %), and significantly higher than the positive control (54 %). In short, both yeast-derived NT and RNA, especially the RNA at the dose of 0.50–0.75 g/kg feed groups, showed promising health benefits effects in the Pacific white shrimp, notably the improved immune function and disease resistance.

The effects of coriander (Coriandrum sativum) seeds on the growth performance, growth hormone, antibacterial capacity, and immune response of European sea bass (Dicentrarchus labrax)

Abstract Coriander seeds are among the functional herbal supplements, but their effects on aquatic animals are still lacking. Herein we evaluated the effects of coriander seeds on the growth performance, growth hormone, antibacterial capacity, and immune response of European sea bass (Dicentrarchus labrax). Fish with initial mean weights of 5.08 ± 0.12 g/fish were allocated in four groups (in triplicate) and fed dietary coriander at 0, 5, 10, and 20 g/kg for 150 days. The growth performance, feed utilization, and survival rate of fish-fed dietary coriander meaningfully increased (P<0.05). The protein efficiency ratio gradually increased (P<0.05) in fish-fed coriander seeds compared with the control. On the other hand, the feed conversion ratio was gradually decreased (P<0.05) in fish-fed coriander seeds comparing with the control. The survival rate was markedly increased (P<0.05) in European sea bass fed dietary coriander regardless of the inclusion level. Further, no differences were seen among fish fed varying levels of coriander (P<0.05). The level of blood growth hormone was markedly higher (P<0.05) in European sea bass fed dietary coriander at 20 g/kg than fish-fed 0 and 5 g/kg. The abundance of intestinal Vibrio spp. and fecal coliform were obviously lower (P<0.05) in fish fed 10 and 20 g/kg than fish fed the coriander-free diet. Further, fish fed 20 g/kg had lower (P<0.05) Vibrio spp. and Faecal Coliform counts than fish fed 10 g/kg. Fish fed dietary coriander had significantly higher (P<0.05) hematocrit, hemoglobin, red blood cells (RBCs), and white blood cells (WBCs) than fish fed the control. The lysozyme and phagocytic activities were meaningfully increased (P<0.05) in fish fed 10 and 20 g/kg compared with fish fed 0 and 5 g/kg of dietary coriander. In conclusion, dietary coriander could be included in the diets at 10–20 g/kg to improve the growth performance, growth hormone, feed utilization, and immune response of European sea bass.

Supplementing the diet of pompano Trachinotus ovatus with MacroGard® to increase innate immunity, intestinal microbes, growth and ammonia tolerance

The present experiment aimed to analyse the advantages of diets containing 0.05%, 0.10% and 0.20% β-glucan on improving the non-specific immunity response, intestinal Vibrio, total aerobic bacteria, growth and ammonia resistance of pompano, Trachinotus ovatus (28.68 ± 0.23 g). After four weeks of diet feeding, the phagocytic index (PI), phagocytic ratio (PR), and serum lysozyme (SL) of pompano increased when adding β-glucan to their diet. The greatest immune response was observed in the pompano fed the feeds containing 0.05% and 0.10% of β-glucan (P≤0.041). Further, on day 28, the total intestinal bacteria were remarkably rose (P≤0.017) in the pompano those were fed 0.05%–0.10% of β-glucan. However, the Vibrio density and the proportion of Vibrio to the aerobic bacteria were considerably higher in pompano fed the basal (P≤0.045). Also, the pompano that offered dietary β-glucan grew faster than the pompano in control. On days 14 and 28, the β-glucan concentration and fish immune response (PR, PI, SL) correlated positively (r≥ 0.379, P≤0.012). Moreover, on day 28, the total intestinal bacteria showed a profound correlation with the β-glucan level (r=0.312, P=0.012). However, the Vibrio to total bacteria ratio increased as the Vibrio count was corresponded negatively to the β-glucan quantity (r= −0.528, P≤ 0.001). On day 28, the β-glucan addition was highly correlated to the phagocytic index (PI) and intestinal Vibrio. The predicted optimum levels of β-glucan to maximise responses of pompano were 0.121% and 0.122% of β-glucan for PI and intestinal Vibrio, respectively. Moreover, under stress ammonia, the pompano that was given β-glucan diets gained better survival rates and lower relative risks than pompano fed the base diet. In conclusion, the 0.05% to 0.10% β-glucan diet could boost the immune activity, improve intestinal microbes, enhance the tolerance capacity to the ammonia of the cultured pompano, T.ovatus.

Evaluation of different dietary n ‐3 lc‐pufa on the growth, intestinal health and microbiota profile of golden pompano ( Trachinotus ovatus )

The omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA), such as docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), are essential fatty acids for marine fish. This study aimed to evaluate different dietary n-3 LC-PUFA on the growth, intestinal health and microbiome in carnivorous marine fish Trachinotus ovatus. Three diets, respectively, supplemented with fish oil, EPA-enriched oil and DHA-enriched oil were fed juvenile T. ovatus for 10 weeks. The results showed that the three groups showed no difference in the growth, histology and digestive enzyme activities of anterior intestine. Moreover, the intestinal ACP and ALP activities and tnfɑ mRNA level were increased in the EPA-enriched group, whereas the serum diamine oxidase activity and intestinal lysozyme activity and malondialdehyde content were decreased in both EPA- and DHA-enriched groups. Meanwhile, these two diets also down-regulated the mRNA expression of Mucin 2, Mucin 13, hes1-b, Krueppel-like factor 4 and Occludin, and up-regulated the zonula occludens-1 mRNA levels in intestine. Moreover, the two groups significantly decreased the intestinal Vibrio abundance and increased the probiotic proportions, especially in the EPA-enriched group. These results indicate dietary n-3 LC-PUFA would facilitate normal intestinal function and probiotics profiles of T. ovatus, and the EPA-enriched group appears to be more positive.

Lactobacillus spp. as probiotics for prevention and treatment of enteritis in the lined seahorse (Hippocampus erectus) juveniles

With the aim of using probiotics to control the enteritis in the lined seahorse Hippocampus erectus, three experiments were carried out. In the first experiment, difference in intestinal microbiota between the healthy and enteritis diseased juveniles was investigated to screen the targeted probiotics to enteritis. The results showed that diseased juveniles were heavily deficient in intestinal Lactobacillus spp. compared with healthy ones. Therefore, three Lactobacillus species of L. acidophilus, L. plantarum and L. rhamnosus were employed in the second experiment to test the preventative effect of Lactobacillus spp. on enteritis. The Lactobacillus spp. was daily administrated to the rearing water containing juveniles and live food (copepods) for 45 days. The survival, growth and intestinal parameters, including Vibrio and lactic acid bacteria, immunocytokines (tumour necrosis factor (TNF)-α, interleukin (IL)-1β, interferon (IFN)-γ and lysozyme (LZM)), and epithelial ultrastructure were analysed on days 15, 30 and 45. The results showed that in the administrated groups, particularly administrated with L. plantarum, the survival and growth, together with the abundance of intestinal lactic acid bacteria, were greatly improved, although no decrease in intestinal Vibrio was noted. IFN-γ and LZM, two cytokines that served as indicators for immune capacity, were at high levels during the whole experimental period. While in the control group, enteritis occurred. During the enteritis occurred period (e.g., day 30), TNF-α and IL-1β, two indicators usually for infection or inflammation, sharply increased, and the abundance of goblet cells reduced. These results confirmed that Lactobacillus spp. has a preventive effect on enteritis, and L. plantarum has a better effect than the other two species. Therefore, different doses (0, 5, 10 and 20 × 108 cfu/L) of L. plantarum were used to treat the enteritis diseased juveniles from an epidemic area in the third experiment. The results showed that in the high doses (10 and 20 × 108 cfu/L) groups, the survival rate (from 20% to >45%) and the abundance of intestinal Lactobacillus (from 0.15% to 2.91%) were greatly elevated, respectively. These results confirmed that high dose of L. plantarum has a treatment effect on enteritis.

Organic acids blend as dietary antibiotic replacer in marine fish olive flounder,Paralichthys olivaceus

The present study was conducted to evaluate the efficacy of organic acid blends as dietary antibiotic replacer in marine fish olive flounder, Paralichthys olivaceus. Fish averaging 3.5 ± 0.05 g (mean ± SD) were fed one of the four experimental diets: (1) without antibiotic or organic acid (Control/CON); (2) with antibiotic—50 mg oxytetracycline per kg body weight per day (OTC); (3) with organic acid blend A—4 g/kg diet (OAA); and (4) with organic acid blend B—4 g/kg diet (OAB), for 10 weeks. At the end of the experiment, total intestinal bacterial counts in fish-fed OAA, OAB and OTC were significantly lower than that of fish-fed CON diet (p < 0.05). Further, the group of fish-fed organic acid blends (OAA, OAB) or antibiotic (OTC)-supplemented diets exhibited lower intestinal Vibrio sp. counts compared with fish-fed CON diet. Disease challenge test with bacteria Edwardsiella tarda showed significantly lower cumulative mortality rates for the group of fish-fed OAA, OAB or OTC than that of fish-fed CON diet (p < 0.05). There were no negative effects on the growth, serological characteristics and proximate composition among the group of fish-fed different experimental diets. Therefore, the present experiment demonstrates that blends of organic acid could be a promising alternative to dietary antibiotics for the preventive and/or curative health management in marine fish olive flounder aquaculture.

Dietary β-glucan improved growth performance, Vibrio counts, haematological parameters and stress resistance of pompano fish, Trachinotus ovatus Linnaeus, 1758.

This study evaluated effects of graded levels of dietary β-glucan (0, 0.5, 1, 2 and 4gkg(-1)) on growth performance, haematological parameters, intestinal Vibrio counts, dose requirement and salinity stress resistance in pompano fish Trachinotus ovatus (6.45g±0.06 (SEM)). After 8-weeks of diet feeding, growth was significantly higher in fish fed diets with 0.10% β-glucan compared to fish fed control diet (no β-glucan). Survival increased significantly in fish fed 0.05 and 0.10% β-glucan compared to control diet. There were significant increases in red blood cells (in 0.20% β-glucan diet), in total leukocytes (in 0.05-0.20% β-glucan diet), in both lymphocyte and monocyte count in fish fed 0.10%-0.40% β-glucan diet. However, dietary β-glucan did not affect neutrophil, eosinophil and basophil counts. Intestinal Vibrio counts were reduced in fish fed any level of β-glucan compared to control. In addition, dietary β-glucan levels highly correlated with growth, survival, intestinal Vibrio counts and haematological index. Optimal β-glucan levels for maximal growth of fish were predicted to be 0.122% at day 21 (R(2)=98.53%), 0.120% at day 28 (R(2)=78.55%), 0.115% at day 42 (R(2)=62.21%) and 0.090% at day 56 (R(2)=75.18%), showing a decreasing β-glucan requirement with increasing fish size. Furthermore, optimal β-glucan levels for maximal haematological parameters based on lymphocyte count, was estimated to be 0.120% (R(2)=98.53%) at day 56. Also, fish fed 0.05%-0.20% β-glucan showed better resistance against salinity stress. In conclusion, β-glucan supplementation is effective for improving growth, intestinal Vibrio counts and boosted stress resistance of the pompano fish, T.ovatus.

Comparison ofVibriospp. populations found in seawater, in exhibition aquaria, in fish intestine and in fish feed

Vibrio populations in the seawater supply and the water of seven exhibition aquaria that simulate various Mediterranean and tropical ecosystems were compared. The similarity of Vibrio populations in the intestine of various fish species, feed and water was examined. Resistance to the antibiotics used in fish health management was analysed for the dominant Vibrio isolates. Samples were collected for 1 year from seven exhibition tanks reproducing different ecosystems. The diversity and population similarity among vibrios were determined using a miniaturized biochemical phenotyping method. Similar Vibrio populations were found in the water supply and in the water of the Mediterranean ecosystems. However, different Vibrio populations were found in the water of tanks with tropical ecosystems. Vibrio populations in the water seemed to have a greater effect on the composition of intestinal Vibrio populations than those in feed. No resistance to antibiotics was observed, indicating their appropriate use for health management. Water characteristics have a greater impact on the composition of Vibrio populations in aquaria and fish intestinal microbiota than bacteria in feed. The microbiological monitoring water could provide valuable information for managing the health of exhibition aquaria.

Protection Against Enteric Bacterial Infection by Secretory IgA Antibodies

Abstract This paper elaborates and extends earlier reports from this laboratory on the mechanisms by which coproantibodies protect against enteric bacterial infection. Purified antibody preparations obtained from the lumen of the intestine of orally vaccinated germfree mice, containing very small amounts of S-IgA but no other serologically active immunoglobulins, were found to protect mice against experimental enteric cholera infection. This protection was associated with a reduction in that fraction of the total vibrio population which was adsorbed to the mucosa. Total counts of intestinal vibrio populations were not affected. The mechanism of this process was investigated by using metabolic inhibitors in experimental infections of intestinal loops of rabbits. Iodoacetate reversed the antibody-mediated shift of the vibrio population away from association with the mucosa. This suggests that the mucosal cell may furnish some accessory factor which, in conjunction with antibody, results in an antibacterial mechanism on the mucosal surface. Iodoacetate had no effect on total vibrio population and adsorption of vibrios in nonimmunized intestinal loops. Consequently, a direct effect of iodoacetate on the vibrios, rather than on the mucosal cells, is a less likely explanation for the observed effects.