Sobria Infection Research Articles

Dietary effects of Saccharomyces cerevisiae and Allium sativum on growth, antioxidant status, hepatic and intestinal histoarchitecture, expression of growth- and immune-related genes, and resistance of Oreochromis niloticus to Aeromonas sobria

This study investigated the benefits of yeast, Saccharomyces cerevisiae and/or garlic, Allium sativum supplementation in diets of Nile tilapia with regard to growth, antioxidant status, hepatic and intestinal histoarchitecture, expression of growth- and immune-related genes, and resistance to Aeromonas sobria infection. Fish (with an initial weight of 9.43 ± 0.08 g) were allocated to twelve hapas, organized into four triplicate treatment groups defined as control (no supplementation), yeast (4 g/kg diet), garlic (30 g/kg diet), and a mixture of both. This trial continued over a 60-day feeding period. Results revealed that combined treatment (yeast + garlic) demonstrated the most promising outcomes regarding growth, with significantly higher final body weights, weight gains, and specific growth rates compared to other groups. Moreover, this combination enhanced hepatic antioxidant status, as evidenced by elevated levels of reduced glutathione and activities of catalase and superoxide dismutase enzymes, reflecting improved defense against oxidative stress. Histological assessments of the livers and intestines demonstrated structural enhancements in yeast and garlic treatments, suggesting improvements in organ health. In comparison to the control, the gene expression analyses unveiled increased expression of growth-related (igf-1 and ghr1) and immune-related (il-10, lyz, and hep) genes in the test groups, indicating a possible reinforcement of the growth and immune responses. The combined treatment also showed the highest resistance to A. sobria infection, as evidenced by improved survival rates and lower mortality compared with the other groups. These findings highlight the benefits of a combination of both yeast and garlic as a dietary supplementation regimen. In conclusion, this study suggests that the combined treatment regimen could be considered an effective strategy to promote the health and productivity of Nile tilapia under production conditions.

Dietary effects of microalga Tetraselmis suecica on growth, antioxidant-immune activity, inflammation cytokines,and resistance of Nile tilapia fingerlings to Aeromonas sobria infection.

The dietary effects of the green microalga Tetraselmis suecica (TS) on the growth, digestive enzymes, immune and antioxidant responses, genes expression,and disease resistance of Nile tilapia (Oreochromis niloticus) fingerlings were investigated. This microalga was mixed with the diet'ingredients at doses of 0.0 (the control), 5, 10, 15,and 20 g/kg diet and then fed to fish daily for 84 days. After the feeding trial, fish were experimentally challenged with Aeromonas sobria, infection and fish mortalities were recorded for another 10days. Dietary TS significantly (p < 0.05) enhanced growth, digestive enzymes activities,and blood proteins, particularly at the level of 15 g/kg diet. Feeding the fish on 15 TS/kg feed exhibited highest mRNA expressions of GH and IGF-1 genes as well as SOD, CAT,and GPx genes compared to other TS groups. Moreover, highest levels of hepatic antioxidant and immune indices were found in the treatment of 15 g TS/kg feed. Significant downregulation of IL-1β and IL-8 genes expression and significant upregulation of IL-10 gene expression were observed in TS-fed fish, principally in fish groups fed on 15-20 g TS/kg feed. Conversely, hepatic malondialdehyde levels, blood glucose,and the activities of transaminases (ALT and AST) were significantly (p < 0.05) decreased in fish fed with 15-20 g TS/kg diet. Serum bactericidal activity against A. sobria was significantly higher in TS-fed fish groups, and its highest levels were found in treatments of 15-20 g/kg diet. Of interest, the survival rates of fish groups fed diets with 10-20 g TS/kg feed were higher after the challenge with A. sobria infection than the control group. Accordingly, we can conclude that supplementing fish diets with a 15 g TS/kg diet enhanced the growth, antioxidant and immune activities,and resistance of Nile tilapia fingerlings to possible A. sobria infection.

Antimicrobial efficacy of magnetite nanoparticles against Aeromonas sobria challenge in African catfish: Biochemical, protein profile, and immuno-antioxidant indices

Recently, researchers in aquaculture become interested in green synthesized nanomaterials as a superior alternative to current conventional methodologies. The present work shows that Moringa oleifera synthesized magnetite nanoparticles (MS-Fe3O4NPs) might offer a possible substitute for common antibiotics to treat Aeromonas sobria infection in African catfish (Clarias gariepinus). MS-Fe3O4NPs demonstrated an in vitro antibacterial potential (21 mm inhibition zone) against A. sobria. The fish (n = 120; average body weight: 90 ± 3.5 g) were randomized into four groups (control, MS-Fe3O4NPs, A. sobria, and MS-Fe3O4NPs + A. sobria), where 1.2 mg/L of MS-Fe3O4NPs was used as bath treatment for seven-days. A. sobria infection caused substantial elevations in malondialdehyde, tumor necrosis factor-alpha, stress indices, and hepato-renal biomarkers as well as a lower survival rate. Moreover, an apparent depletion in the level of antioxidants, the protein profile, and immune indicators were the consequences of A. sobria infection. Surprisingly, treatment of A. sobria-infected fish with MS-Fe3O4NPs recovered these parameters. Hence, MS-Fe3O4NPs as a water additive show promise as an antibacterial treatment against A. sobria in fish.

The effect of dietary Crataegus Sinaica on the growth performance, immune responses, hemato-biochemical and oxidative stress indices, tissues architecture, and resistance to Aeromonas sobria infection of acrylamide-exposed Clarias gariepinus

This study investigated the effect of using a natural dietary supplement of Crataegus Sinaica (CS) to mitigate the negative impacts of waterborne acrylamide (ACR) on the health and performance of freshwater fish, African catfish (Clarias gariepinus). For this aim, 270 fish were divided into six groups (45 fish/group). Three groups were kept in non-contaminated water and fed a non-fortified basal diet, 1% CS, and 2% CS. The other three groups were exposed to ACR (26.6 mg/L water) and fed a basal diet, 1% CS, and 2% CS. After 60 days, the growth performance, liver and kidney function, stress indicators, oxidative stress indices, immunological response, vital tissue architecture, and resistance to Aeromonas sobria have been evaluated. Results indicated that CS dietary supplementation (1% and 2% CS) significantly counteracted ACR-induced reduced growth and survival. Furthermore, both CS dietary supplementation significantly balanced the ACR-induced leukopenia, anemia, hypoalbuminemia, hypoglobulinemia, and hypoproteinemia. Likewise, 1% and 2% CS addition to the ACR-exposed fish diets significantly reduced the ACR-induced increase in serum enzymes, bilirubin, renal damage products, hyperglycemia, and cortisol. Instead, the ACR-evoked depletion of antioxidant (glutathione peroxidase, superoxide dismutase, catalase, and reduced glutathione) and innate immune (lysozyme, complement3, and nitric oxide) components were significantly restored by both CS dietary supplementation. Besides, the ACR-induced pathological alterations in hepatic, renal, and splenic tissues were considerably lessened by CS. Besides, the reduced disease resistance of ACR-exposed fish was restored when challenged with A.sobria in a fish-fed 1% and 2% CS-fortified diet. Noteworthy, the inclusion of 2% CS produced better results than 1%. Overall, feeding C. gariepinus a diet supplemented with 2% CS significantly improved the fish's overall health, growth, and disease resistance, despite the ACR water pollution that consequently would sustain aquaculture.

Antioxidant, Immunostimulant, and Growth-Promoting Effects of Dietary Annona squamosa Leaf Extract on Nile Tilapia, Oreochromis niloticus, and Its Tolerance to Thermal Stress and Aeromonas sobria Infection.

Plant extracts are a phytochemically-rich alternative to antibiotic and synthetic feed additives, with high systemic bioactivity in animals. The present study aimed to evaluate the effect of a hydroalcoholic extract of custard apple (Annona squamosa) leaf (ASLE) on the growth, hematobiochemical parameters, digestive enzyme activities, redox status, nonspecific immune response, and cold and bacterial infection tolerance in Nile tilapia (Oreochromis niloticus). A total of 300 Nile tilapia fingerlings (11.87 ± 0.48 g) were fed ASLE-supplemented diets at increasing levels of 0, 5, 10, 15, and 20 g/kg for 60 days. At the end of the feeding period, the fish were experimentally challenged with cold water stress or Aeromonas sobria, and mortalities were recorded for 10 days. The results revealed that the growth performance and feed conversion ratio were significantly improved with an increasing level of ASLE supplementation. The hematologic profile and hepato-renal functions were retained within a healthy range in the various groups supplemented with an ASLE diet. Antioxidant status was significantly improved in the serum of fish fed ASLE-supplemented diets, in terms of superoxide dismutase (SOD), catalase (CAT) activities, reduced glutathione, and total antioxidant capacity. Meanwhile, the myeloperoxidase (MPO) and malondialdehyde (MDA) levels decreased significantly. Similarly, there was a noticeable improvement in the hepatic CAT and SOD activities and a reduction of hepatic MDA. Marked improvements in lysozyme activity, nitric oxide production, complement3 level, and phagocytic activity were recorded in groups fed ASLE-supplemented diets, which peaked with the 20 g ASLE/kg diet. Moreover, the serum glucose and cortisol levels significantly declined in groups fed ASLE at levels of 15-20 g/kg compared to the other groups. Supplementation with ASLE increased the activities of protease, lipase, and α-amylase. ASLE supplementation at a concentration of 10-20 g/kg diet enhanced the resistance of Nile tilapia to A. sobria infection. According to this study, ASLE supplementation enhanced the antioxidant balance, non-specific immune response, physiological status, resistance against infection, and growth performance of Nile tilapia at supplementation levels of 10-20 g/kg diet.

Imidacloprid toxicity in Clarias gariepinus: Protective role of dietary Hyphaene thebaica against biochemical and histopathological disruption, oxidative stress, immune genes expressions, and Aeromonas sobria infection

Recently, there has been a controversy about the hazards of toxic substances released to the aquatic biota. Therefore, the current context is the first attempt to assess the ability of a beneficial medicinal plant, Hyphaene thebaica fruit (HTF) to mitigate various toxic impacts in Clarias gariepinus induced by imidacloprid (IMI) including immune depression, protein impairment, oxidative stress, hepato-renal dysfunction, histopathological, and immune-histochemical alterations. The molecular responses of IMI-induced toxicity at the molecular level and to recognize critical genes altered in response to toxicity are documented. Additionally, we investigated the fish resistance post-challenging with a pathogenic zoonotic bacterium, Aeromonas sobria. Fish (N = 240) were randomly allotted into four random groups in triplicate. The first (control) and second (HTF) groups were fed on basal diets that were enriched with 0.0 and 15 g kg−1 of HTF without IMI exposure. The third and fourth groups were fed on the same diets and exposed to 1/5 of the 96-h of LC50 of IMI (2.03 μg L−1) for 60 days. The findings clarified that the IMI exposure significantly augmented (p < 0.05) serum alanine (ALT), aspartate amino-transferases (AST), urea, and creatinine besides malondialdehyde (MDA) levels. While the activities of the protein profile (total protein, albumin, and globulin), immune parameters (lysozyme and immunoglobulin M), and hepatic antioxidant enzymes (superoxide dismutase and glutathione peroxidase) revealed marked depressions in comparison to the control. Histological and immune-histochemical alterations in liver and kidney tissues including vacuolation, severe necrosis, and degeneration, besides weak B-cell lymphoma 2 (BCL-2), potent caspase-3, and down-regulation of genes (IL-1β, IL-8, TNF-α, TGF-β, TLR-5, LYSG, LYSC, NF-κβ, CC, and MYE) were noticed in the IMI-exposed group compared to the control. After 60 days of experimental trial, C. gariepinus challenged by A. sobria exhibited sluggish movement, fin rot accompanied with hemorrhages in different body parts, and severe skin ulcerations with the highest cumulative mortality (80%). Surprisingly, HTF-dietary inclusion enhanced these variables by almost renovating to control values by maintaining histological architecture of the hepatic and renal tissues. Additionally, it increased the fish resistance against A. sobria indicated by reduced mortalities (40%) and enhanced clinical picture. The outputs of the recent study recommend the HTF-dietary supplement to protect against the IMI toxicity in C. gariepinus. And provide insights into the future application of the HTF as an anti-toxic, immune-stimulant, antioxidant, and antibacterial, for improving fish health and sustaining aquaculture. To avoid the deleterious toxic impacts of IMI, this pesticide must be applied carefully, especially near water bodies.

Effect of Aeromonas sobria infection on gills and skin histopathology of the Nile tilapia reared under biofloc and clear water systems

Effect of Aeromonas sobria infection on gills and skin histopathology of the Nile tilapia reared under biofloc and clear water systems

Myo-Inositol Restores Tilapia's Ability Against Infection by Aeromonas sobria in Higher Water Temperature.

Bacterial infection presents severe challenge to tilapia farming, which is largely influenced by water temperature. However, how water temperature determines tilapias’ survival to infection is not well understood. Here, we address this issue from the perspective of metabolic state. Tilapias were more susceptible to Aeromonas sobria infection at 33°C than at 18°C, which is associated with differential metabolism of the fish. Compared to the metabolome of tilapia at 18°C, the metabolome at 33°C was characterized with increased an tricarboxylic acid cycle and a reduced level of myo-inositol which represent the most impactful pathway and crucial biomarker, respectively. These alterations were accompanied with the elevated transcriptional level of 10 innate immune genes with infection time, where il-1b, il-6, il-8, and il-10 exhibited a higher expression at 33°C than at 18°C and was attenuated by exogenous myo-inositol in both groups. Interestingly, exogenous myo-inositol inactivated the elevated TCA cycle via inhibiting the enzymatic activity of succinate dehydrogenase and malate dehydrogenase. Thus, tilapias showed a higher survival ability at 33°C. Our study reveals a previously unknown relationship among water temperature, metabolic state, and innate immunity and establishes a novel approach to eliminate bacterial pathogens in tilapia at higher water temperature.

Aeromonas sobria regulates proinflammatory immune response in mouse macrophages via activating the MAPK, AKT, and NF-κB pathways.

Aeromonas sobria, a Gram-negative bacterium that can colonize both humans and animals, is found in a variety of environments, including water, seafood, meat, and vegetables (Cahill, 1990; Galindo et al., 2004; Song et al., 2019). Aeromonas spp. are conditionally pathogenic bacteria in aquaculture, which can rapidly proliferate, causing disease and even death in fish, especially when the environment is degraded (Neamat-Allah et al., 2020, 2021a, 2021b). In developing countries, Aeromonas spp. have been associated with a wide spectrum of infections in humans, including gastroenteritis, wound infections, septicemia, and lung infections (San Joaquin and Pickett, 1988; Wang et al., 2009; Su et al., 2013). Infections caused by Aeromonas spp. are usually more severe in immunocompromised individuals (Miyamoto et al., 2017). The presence of a plasmid encoding a β‍-lactamase in A. sobria that confers resistance to β-lactam antibiotics poses a huge challenge to the treatment of diseases caused by this microorganism (Lim and Hong, 2020). Consequently, an in-depth understanding of the interaction between A. sobria and its hosts is urgently required to enable the development of effective strategies for the treatment of A. sobria infections.

Aeromonas sobria Induces Proinflammatory Cytokines Production in Mouse Macrophages via Activating NLRP3 Inflammasome Signaling Pathways.

Aeromonas sobria, a common conditional pathogenic bacteria, is widely distributed in the environment and causes gastroenteritis in humans or septicemia in fish. Of all Aeromonas species, A. sobria is the most frequently isolated from human infections especially in immunocompromised subjects. Innate immunity is the first protection system of organism to resist non-specific pathogens invasion; however, the immune response process of hosts against A. sobria infection re\\mains unexplored. The present study established an A. sobria infection model using primary mouse peritoneal macrophages (PMφs). The adherence and cytotoxicity of A. sobria on PMφs were determined by May-Grünwald Giemsa staining and LDH release measurement. Pro-inflammatory cytokine expression levels were measured using qPCR, western blotting, and ELISA methods. We also investigated the levels of ASC oligomerization and determined the roles of active caspase-1 in IL-1β secretion through inhibition assays and explored the activated pattern recognition receptors through immunofluorescence. We further elucidated the roles of activated inflammasome in regulating the host’s inflammatory response through inhibition combined with ELISA assays. Our results showed that A. sobria induced lytic cell death and LDH release, whereas it had no adhesive properties on PMφs. A. sobria triggered various proinflammatory cytokine transcription level upregulation, and IL-1β occupied the highest levels. The pro-IL-1β protein expression levels increased in a dose-dependent manner with MOI ranging from 1 to 100. This process was regulated by ASC-dependent inflammasome, which cleavage pro-IL-1β into active IL-1β p17 with activated caspase-1 p20. Meanwhile, the expression levels of NLRP3 receptor significantly increased, location analysis revealed puncta-like surrounding nuclear, and inhibition of NLRP3 inflammasome downregulated caspase-1 activation and IL-1β secretion. Blocking of NLRP3 inflammasome activation through K+ efflux and cathepsin B or caspase approaches downregulated A. sobria–induced proinflammatory cytokine production. Overall, these data indicated that A. sobria induced proinflammatory cytokine production in PMφs through activating NLRP3 inflammasome signaling pathways.

Citrullus colocynthis extract and synthesized Selenium nanoparticles enhance non‐specific response and resistance against Aeromonas sobria in Nile tilapia ( Oreochromis niloticus )

The effects of Citrullus colocynthis extract (CCE) and synthesized Se nanoparticles (Nano-Se) on non-specific immune response and resistance to Aeromonas sobria in Nile tilapia (Oreochromis niloticus) were investigated. Treatments included three levels of Nano-Se (0.5, 1 and 2 mg/kg of feed), three levels of CCE (0.1%, 0.3% and 0.5%) and control group (no additives). The diets were fed for 4 weeks, and biochemical indices, serum lysozyme, respiratory burst activities and antioxidant enzymes were measured on weeks 1, 2 and 4. After 4 weeks of feeding, fish were infected with A. sobria and mortalities were recorded for 14 days. Results of this study showed that feeding tilapia with CCE and Nano-Se supplements significantly enhanced biochemical indices, serum lysozymes and respiratory burst. CCE treatments had a moderate effect on superoxide dismutase and no effect on the other antioxidant enzymes. Nano-Se treatments had significantly positive effects on antioxidant enzymes. Both CCE and Nano-Se supplements reduced mortality following A. sobria infection. The lowest mortality (13%) was observed in the group fed with 2 mg/kg Nano-Se, and the highest mortality of 90% was observed in the control group. It can be concluded that C. colocynthis extract and synthesized Nano-Se supplementation added to fish feed can act as immunostimulants and enhance the immune functionality, antioxidant status and disease resistance in cultured Nile tilapia (O. niloticus).

Chitosan vitamin E nanocomposite ameliorates the growth, redox, and immune status of Nile tilapia (Oreochromis niloticus) reared under different stocking densities

A 70-days feeding investigation was undertaken to highlight the influence of dietary incorporation with the conventional form of vitamin E (VE) and chitosan vitamin E nanocomposite (CVEN) on different health aspects of Oreochromis niloticus (O. niloticus) reared under different stocking densities. Growth performance, antioxidant status, and immune response were assessed. Fish (n = 405, average weight: 14.74 ± 0.06 g) were randomly assigned into six groups in triplicates. Three experimental diets were used; 1) basal diet with no additives, 2) basal diet +300 mg/kg VE, 3) basal diet +300 mg/kg CVEN, with two stocking densities for each; standard stocking density (SSD) (15 fish/ aquaria) and high stocking density (HSD) (30 fish/ aquaria). Furthermore, a subsequent challenge with pathogenic Aeromonas sobria (A. sobria) was performed at the end of the feeding period. A significant improvement in the final body weight, total weight gain, feed intake, specific growth rate, and average daily weight gain was found in the CVEN group raised under SSD. Vitamin E supplementation, especially the nano form (CVEN), ameliorates the bad effect of high stocking density on fish growth. Marked elevation in the serum level of vitamin E and growth hormone and decreased AST and ALT levels were observed in the CVEN group reared under SSD compared with other groups. An improvement in the serum and hepatic antioxidant activities and the immunological indicators (lysozyme activity, nitric oxide, phagocytic index, and IL-10) was observed in Vitamin E supplemented groups reared under SSD. Supplementation of vitamin E, especially the nano form, improved the serum and hepatic antioxidant enzymes and decreased lipid peroxidation of fish reared under HSD. Increased survivability of fish reared under HSD by CVEN supplementation. Vitamin E supplementation counteracts the negative impact of HSD on the histoarchitecture of the liver. This study suggested that; supplementation of the fish diet with CVEN (300 mg/kg) could promote the growth performance, antioxidant status, immune response, and increase fish tolerance to rearing under HSD. Moreover, dietary supplementation with CVEN enhanced fish resistance to A. sobria infection.

Acute Lymphoblastic Leukemia in Children with Aeromonas veronii biovar sobria Infection: a Case Report and Review of the Literature

Acute Lymphoblastic Leukemia in Children with Aeromonas veronii biovar sobria Infection: a Case Report and Review of the Literature

Influence of Feeding Quinoa (Chenopodium quinoa) Seeds and Prickly Pear Fruit (Opuntia ficus indica) Peel on the Immune Response and Resistance to Aeromonas sobria Infection in Nile Tilapia (Oreochromis niloticus).

Simple SummaryThe inclusion of dietary supplements as feed additives in fish feed promotes the growth, immunity, and health of the fish, thereby accomplishing extraordinary outcomes in the net gain of the farm. Therefore, the present study was conducted to evaluate the influence of using quinoa seeds (QU) and prickly pear fruit peel (PP) as dietary supplements for fish, at the dose levels of 10% and 20% of the diet, on the immune response and disease resistance against pathogens, providing a novel perspective in aquaculture. Our findings indicated that the inclusion of PP and QU into the diets of Nile tilapia (Oreochromis niloticus) as feed supplements improved the survival rate, as well as the hematological, digestive, antioxidant, and immunological parameters. Moreover, an improvement in the strength of Nile tilapia immune response against Aeromonas sobria (A. sobria) infection was observed, evidenced by the improvement in the survival rate of infected fish. This was accomplished through the protection of the hepatic tissue and modulation of the expression of immune-encoding genes, including the downregulation of the gene encoding TGF-β and upregulation of the IFN-γ-encoding gene. Moreover, histological restoration of the morphological structures of intestine, liver, and spleen tissues was observed, particularly at the supplementation level of 20%.In recent times, nutraceuticals have been used extensively to identify promising feed additives for the improvement of the aquaculture industry through the enhancement of growth and survival rates, potentiation of the immune responses, and fortification of the resistance against infectious bacterial diseases. In this study, Nile tilapia (Oreochromis niloticus) were fed with diets supplemented with quinoa seeds (QU) or prickly pear fruit peel (PP) at the dose levels of 10% or 20% of the diet. After 45 days of the feeding trial, the fish were exposed to Aeromonas sobria (A. sobria) challenge. The pre-challenge indices indicated that both supplements mediated a significant improvement in most of the estimated parameters, including survival rate, antioxidant status, hematological and immunological indices, and hepatoprotective potential. These effects were recorded in the groups fed with high doses of the supplements (20%). The least changes were observed in the QU10-supplemented fish. In the spleen tissue, the TGF-β gene was upregulated in the PP10-, PP20- and QU20-supplemented groups, while the expression of the IFN-γ gene remained unaffected in all the supplemented groups, except for the PP20-supplemented group, which showed an upregulation. After the challenge with A. sobria, the relative survival percentage was improved by the supplementation of PP and QU, particularly in the PP20-supplemented group, possibly via the promotion of immunological responses, hepatoprotective potency, and modulation of the studied genes. Moreover, the morphological structure of the tissues showed marked recovery. The findings suggest that Nile tilapia fed with different levels of PP peel and QU seeds, particularly at the level of 20%, enhanced the immune response in fish and improved their resistance against A. sobria infection.

Effect of Rosemary (Rosmarinus officinalis) and Sage (Salvia officinalis) Essential Oils on Disease Resistance against Aeromonas sobria in Goldfish (Carassius auratus)

In this study, the chemical composition and the antibacterial properties against Aeromonas sobria of the essential oils of rosemary and sage in gold fish were evaluated in vitro and in vivo for the first time. The major constituents were eucalyptol (26.36 %) and camphor (29.17 %) for rosemary essential oil and eucalyptol (27.08 %), thujone (20.52 %) and camphor (16.99 %) for sage oil. In vitro antibacterial effects of essential oils against A. sobria were detected by agar diffusion assay. The in vitro antibacterial effect of rosemary (20±2.82 mm) and sage (18.5±2.12 mm) essential oils (1000 µl ml-1) were determined to be strong against A. sobria (p˂0.05). The effects of the essential oils on the disease resistance of goldfish were also investigated. Fish (5±0.15 g) were fed with different concentrations (0, 1.0 and 3.0 ml kg-1) of each essential oil for 45 days. After feeding, the fish were challenged with A. sobria. Dietary administration of sage essential oil (1.0 and 3.0 ml kg-1) and rosemary oil (3 ml kg-1 ) resulted in a significant reduction in mortality due to A. sobria compared to control fish. Our results suggest that these plant oils could provide an alternative for A. sobria infection control in aquaculture.

The Effects of Dietary Administration with High Level Red Pepper (Capsicum annuum) on Growth Performance, Coloration, Histology and Protection Against Aeromonas sobria in Yellow Tail Cichlid, Pseudotropheus acei

The present study was conducted to determine the effects of high level red pepper supplementation to diet on the growth performance, coloration, histology, intestinal microflora and protection against Aeromonas sobria in Pseudotropheus acei. Two isonitrogenous (37% crude protein) and isocaloric (3831kcall/kg energy) experimental diets were prepared by adding of 15 % pepper meal to control diet. The feeding trial was conducted in triplicate for 90 day in aquariums (100-L). At the beginning of the experiment, twenty fish (initial weight 0.06 g) were stocked into each aquarium. The end of the experiment, fish fed red pepper supplemented to diets did not have any marked effect on the weight gain, feed conversion ratio, specific growth rate and survival. However, tail of female fish fed diet containing red pepper was showed increase significantly in pigmentation. High level red pepper addition to diet caused no pathological findings in any organs. Red pepper didn’t observed significant differences for protection to A. sobria infection. However, Aeromas and Pseudomonas counts in red pepper group were significantly lower than control groups.

Effects of dietary probioticLactobacillus plantarumand whey protein concentrate on the productive parameters, immunity response and susceptibility of Nile tilapia,Oreochromis niloticus(L.), toAeromonas sobriainfection

Immunostimulatory feed supplements have an increasingly interest in aquaculture management. Generally, an individual supplement was used in fish diets but it is expected that the use of multi‐supplements may show synergistic enhancements in fish performance, health, and immunity. Therefore, the present investigation was carried out to evaluate the use of dietary probiotic Lactobacillus plantarum and whey protein concentrate (WPC) in practical diets for Nile tilapia, Oreochromis niloticus. Hence, probiotic L. plantarum, WPC and their mixture were incorporated into a basal fish diet (300 g/kg crude protein) as follows: T1 = a basal control diet, T2 = a basal diet containing L. plantarum, T3 = a basal diet containing 1.0 g WCP/kg diet and T4, T5 or T6 = basal diets containing probiotic L. plantarum + 1.0, 2.0 or 3.0 g WCP/kg diet, respectively. Fish (15.2 ± 0.6 g) were fed on one of the tested diets up to apparent satiation twice a day for 60 days. After that, fish were intraperitoneally injected with pathogenic bacteria Aeromonas sobria and fish mortality was observed for 10 days postchallenge. Fish growth and feed intake were significantly improved by dietary probiotic L. plantarum (T2) and/or WPC (T3) over the control group (T1), and highest fish performance was observed in T5–T6 fish groups. Similarly, highest values of haematocrit, glucose, total proteins, albumin, and globulin were significantly observed in T5–T6 fish groups. Likewise, fish fed dietary probiotic L. plantarum (T2), WPC (T3), and their mixture (T4–T6) showed antioxidants and immune‐stimulating activities better than the control group. Fish fed the control diet were more susceptible to A. sobria infection showing highest fish mortality (75.0%). Meanwhile, dietary probiotic L. plantarum (T2), WPC (T3), and their mixture (T4–T6) enhanced significantly the fish resistance to A. sobria infection resulting in maximum values of relative percent of fish survival (73.3%–80.0%) in T5–T6 groups. The present investigation recommended the use of probiotic L. plantarum with 2.0 g WPC/kg diet to improve the growth, antioxidant, immunity responses and tolerance of Nile tilapia to A. sobria infection.

Antimicrobial activities of chitosan nanoparticles against pathogenic microorganisms in Nile tilapia, Oreochromis niloticus

Nanotechnology is a recent unique technique generally used for nutrition and therapy purposes among others. In this respect, the present study was carried out to evaluate the antimicrobial activity of chitosan nanoparticles (CNP) against various microorganisms (fungi and bacteria) isolated from diseased or health Nile tilapia, Oreochromis niloticus. The CNP was prepared based on the ionic gelation of chitosan with tripolyphosphate anion and its mean size was 35 nm with a narrow size distribution and zeta potential of 61.2 mV. The lethal dose of pathogenic bacterial isolates for Nile tilapia was successfully standardized. Clinical signs including weakness, slower movement, swimming closer to the surface, fin hemorrhages, and red patches at the gut regions were observed. Enlargement of spleen followed by tissue necrosis along with signs of hemorrhagic septicemia was also seen in infected fish. Fungal and bacterial isolates were exposed to different CNP doses and it is noticed that CNP inhibited all examined fungal and bacterial isolates in a dose-dependent manner. However, high CNP doses (80 μg/ml) gave highest inhibition zones where Aspergillus flavus, Mucor sp., and Candida sp. were more susceptible, whereas Aspergillus niger, A. fumigatus, and Fusarium sp. were more resistant. Similarly, largest inhibition zones of tested bacteria were obtained at high CNP dose (20 μg/ml). And Aeromonas sobria, A. hydrophila, and Pseudomonas aeruginosa were the most susceptible bacterial strain; meanwhile, Staphylococcus aureus and Pseudomonas fluorescens were the most resistant ones. The minimal inhibitory concentration of CNP against the examined bacteria ranged from 0.156 to 2.5 μg/ml causing their minimal counts. The transmission electron microscope images revealed that CNP showed antagonistic action against A. hydrophila causing disruption of cell membranes and the leakage of cytoplasm. In a practical experiment, Nile tilapia fed dietary CNP at levels of 0.0 and 1.0 g/kg diet for 3 weeks and post-challenged with different pathogenic bacteria via intraperitoneal injection. It is noticed that fish fed a CNP-enriched diet showed less mortality with all bacterial strains (6.7–20%), while, fish fed a CNP-free diet showed highest mortality (66.7–100%). The dietary CNP protected Nile tilapia efficiently against A. hydrophila, A. sobria, and Streptococcus agalactiae infections with relative level of protection (RLP) value of 93.3%, while the RLP against Staphylococcus aureus was 70.0%.

Characterization and Pathology of Aeromonas veronii Biovar Sobria from Diseased Sheatfish Silurus glanis in China

Aeromonas spp., is an important opportunistic pathogen responsible for great economic losses in aquaculture. In this paper, we report our study of an Aeromonas infection that occurred in cultured sheatfish Silurus glanis in May 2016 in a farm in Tianjin city. Typical external symptoms included petechial skin hemorrhages, ascitic distension of the abdomen, redness and swelling of the anus. The isolate SAV-165 from the diseased fish was identified as A. veronii biovar sobria by biochemical properties and molecular techniques. Experimental challenge showed that a 50% lethal dose (LD50) of SAV-165 was 1.59 × 106 CFU/ml in zebrafish Danio rerio. The antimicrobial susceptibility test indicated that the isolate was susceptible to aminoglycosides and chloramphenicol, but resistant to penicillins and sulphonamides. Histopathological examination showed fatty changes and swelling of hepatocytes in the liver, congestion in the submucosa of intestine and the renal veins of the kidney. This is the first report of A. veronii biovar sobria infection in S. glanis in China.

Evaluation of intraepithelial lymphocytes, goblet cells and immunoglobulin genes in the intestinal mucosal tissue of Pelodiscus sinensis after challenge with Aeromonas veronii bv. sobria and lipopolysaccharide

Pelodiscus sinensis, which is a high-value commercial freshwater species, frequently suffers from infectious diseases induced by various pathogens. The mucosa has been confirmed to contribute to host protection, which is the first line of defence against invading pathogens, including bacteria. This study was conducted to evaluate the intestinal mucosal immunity of P. sinensis against Aeromonas veronii bv. sobria and lipopolysaccharide (LPS) infection. A significant increase in the number of intraepithelial lymphocytes (IEL) and goblet cells was observed from 12 h after challenge with A. veronii bv. sobria and LPS (P < 0.01), and the peak was observed at 48 h. The expression of immunoglobulin M (IgM) mRNA also increased between 12 h and 24 h and then decreased until 96 h. Across the experiment, the expression of IgM mRNA in the challenge groups was significantly higher than that in the control group, except at 48 h (P < 0.01), and then declined until 96 h. In contrast, the expression of IgD mRNA had no significant differences compared with the control group. This result showed that the IEL, goblet cells and IgM in P. sinensis were involved in the intestinal mucosal immunity against A. veronii bv. sobria and LPS infection.