Monitoring of different vibrio species affecting marine fishes in Lake Qarun and Gulf of Suez: Phenotypic and molecular characterization

Vibriosis is a globally threatening bacterial disease affecting mariculture with high mortalities and severe economic losses. Isolation and Identification of different vibrio species were performed to a total number of one hundred moribund and freshly dead Solea aegyptiaca, Epinephelus marginatus and Mugil cephalus collected from Lake Qarun and Gulf of Suez. Phenotypic picture and molecular identification based on use of 16SrRNA gene sequence confirmed 44 strains as vibrio species. Further molecular identification of retrieved vibrio spp. using species specific primers for collagenase, ToxR and Vvh genes categorized 10 isolates belong to V. alginolyticus, 8 isolates belong to V. parahaemolyticus and 6 isolates belong to V. vulnificus. The total prevalence of vibriosis was 44% where the highest prevalence was recorded in Lake Qarun examined fishes

Efficacy of dietary yeast cell wall supplementation on the nutrition and immune response of Nile tilapia

Prebiotics are non-digestible carbohydrates that improve the animal health via modulation of their intestinal beneficial organisms. Immunowall® is a commercial prebiotic consists of high concentration of yeast β-glucan (βG) and Mannan-oligosaccharides (MOS). The current study was designed to investigate the prebiotic potential of Immunowall® on nutrition and health performance of Nile tilapia Oreochromis niloticus. Three fish groups were nourished on control diet supplemented with 0%, 0.1% and 0.2% Immunowall® for two months. Both dietary levels of Immunowall® exhibited significant increase in growth parameters (P ≤ 0.05) as well as in white blood cell count, total protein, and globulin concentrations. While, the immune parameters such as antioxidant biomarkers (catalase and glutathione-reductase), non-specific immune response (e.g. phagocytic activity, phagocytic index and lysozyme activity) and immune-related genes expressions (e.g. TNF-α and IL-1β) were higher in 0.2% Immunowall® compared to 0.1% Immunowall® and control. Oral administration of β-glucan and MOS mixture reduced the mortalities after microbial infections with L. gravieae and A. hydrophila. Therefore, we can recommend the dietary inclusion of Immunowall® in aqua-feed as an efficient method to achieve feasible and sustainable fish production. Keywords: β-Glucan, MOS, Immunity, Growth, Challenge, Nile tilapi

Neem leaf powder (Azadirachta indica) mitigates oxidative stress and pathological alterations triggered by lead toxicity in Nile tilapia (Oreochromis niloticus)

Abstract This study investigated the clinical and pathological symptoms of waterborne lead toxicity in wild Nile tilapia collected from a lead-contaminated area (the Mariotteya Canal: Pb = 0.6 ± 0.21 mg L−1) and a farmed fish after 2 weeks of experimental exposure to lead acetate (5–10 mg L−1) in addition to evaluating the efficacy of neem leaf powder (NLP) treatment in mitigating symptoms of lead toxicity. A total of 150 fish (20 ± 2 g) were alienated into five groups (30 fish/group with three replicates). G1 was assigned as a negative control without any treatments. Groups (2–5) were exposed to lead acetate for 2 weeks at a concentration of 5 mg L−1 (G2 and G3) or 10 mg L−1 (G4 and G5). During the lead exposure period, all groups were reared under the same conditions, while G3 and G5 were treated with 1 g L−1 NLP. Lead toxicity induced DNA fragmentation and lipid peroxidation and decreased the level of glutathione and expression of heme synthesis enzyme delta aminolaevulinic acid dehydratase (ALA-D) in wild tilapia, G2, and G4. NLP could alleviate the oxidative stress stimulated by lead in G3 and showed an insignificant effect in G5. The pathological findings, including epithelial hyperplasia in the gills, edema in the gills and muscles, degeneration and necrosis in the liver and muscle, and leukocytic infiltration in all organs, were directly correlated with lead concentration. Thus, the aqueous application of NLP at 1 g L−1 reduced oxidative stress and lowered the pathological alterations induced by lead toxicity

A First Report of Molecular Typing, Virulence Traits, and Phenotypic and Genotypic Resistance Patterns of Newly Emerging XDR and MDR <i>Aeromonas veronii</i> in <i>Mugil seheli</i>

Aeromonas veronii is associated with substantial economic losses in the fish industry and with food-borne illness in humans. This study aimed to determine the prevalence, antibiogram profiles, sequence analysis, virulence and antimicrobial resistance genes, and pathogenicity of A. veronii recovered from Mugil seheli. A total of 80 fish were randomly gathered from various private farms in Suez Province, Egypt. Subsequently, samples were subjected to clinical, post-mortem, and bacteriological examinations. The retrieved isolates were tested for sequence analysis, antibiogram profile, pathogenicity, and PCR detection of virulence and resistance genes. The prevalence of A. veronii in the examined M. seheli was 22.5 % (18/80). The phylogenetic analyses revealed that the tested A. veronii strains shared high genetic similarity with other A. veronii strains from India, UK, and China. Using PCR it was revealed that the retrieved A. veronii isolates harbored the aerA, alt, ser, ompAII, act, ahp, and nuc virulence genes with prevalence of 100%, 82.9%, 61.7%, 55.3%, 44.7%, 36.17%, and 29.8%, respectively. Our findings revealed that 29.8% (14/47) of the retrieved A. veronii strains were XDR to nine antimicrobial classes and carried blaTEM, blaCTX-M, blaSHV,tetA, aadA1, and sul1 resistance genes. Likewise, 19.1% (9/47) of the obtained A. veronii strains were MDR to eight classes and possessed blaTEM, blaCTX-M, blaSHV,tetA, aadA1, and sul1 genes. The pathogenicity testing indicated that the mortality rates positively correlated with the prevalence of virulence-determinant genes. To our knowledge, this is the first report to reveal the occurrence of XDR and MDR A. veronii in M. seheli, an emergence that represents a risk to public health. Emerging XDR and MDR A. veronii in M. seheli frequently harbored aerA, alt, ser, ompAII, and act virulence genes, and blaTEM, sul1, tetA, blaCTX-M, blaSHV, and aadA1 resistance genes

Analysis of the Productivity, Immunity, and Health Performance of Nile Tilapia (Oreochromis niloticus) Broodstock-fed Dietary Fermented Extracts Sourced from Saccharomyces cerevisiae (Hilyses): A Field Trial

The present study aimed to evaluate the effect of dietary fermented extracts sourced from Saccharomyces cerevisiae (nucleotides, β-glucans and MOS) (Hilyses®) on the production and health of Nile tilapia (Oreochromis niloticus) broodstock, as well as on seed survival and performance. The trial was performed in a hatchery along the spawning season and continued in the laboratory to monitor the performance in fry and fingerlings. The broodstock were divided into two groups, (C) fed a basal diet and (H) fed 0.4% Hilyses. Blood and histological parameters, antioxidant power, cortisol level and the expression of some immune-related (TLR-2, IL-1β and TNF-α) and growth-related genes (MUC-2 and IGF-1) were measured. The obtained seeds were subdivided into four treatments: (C-C) fed a basal diet, (C-H) fed 0.4% Hilyses, (H-C) fed a basal diet and (H-H) fed 0.4% Hilyses. Results revealed that the dietary inclusion of Hilyses in the broodstock increased seed production, survival, hematological parameters, and antioxidant power. Moreover, it improved the intestinal microstructure and upregulated the immune- and growth-related genes. The growth indices of fry and fingerlings were significantly increased in all Hilyses-treated groups (p &lt; 0.05). The performance in the (H-H) group significantly surpassed those of all groups. Therefore, dietary fermented yeast could be used as a strategic solution to sustain tilapia production

Antiparasitic and Antibacterial Functionality of Essential Oils : An Alternative Approach for Sustainable Aquaculture

Using synthetic antibiotics/chemicals for infectious bacterial pathogens and parasitic disease control causes beneficial microbial killing, produces multi-drug resistant pathogens, and residual antibiotic impacts in humans are the major threats to aquaculture sustainability. Applications of herbal products to combat microbial and parasitic diseases are considered as alternative approaches for sustainable aquaculture. Essential oils (EOs) are the secondary metabolites of medicinal plants that possess bioactive compounds like terpens, terpenoids, phenylpropenes, and isothiocyanates with synergistic relationship among these compounds. The hydrophobic compounds of EOs can penetrate the bacterial and parasitic cells and cause cell deformities and organelles dysfunctions. Dietary supplementation of EOs also modulate growth, immunity, and infectious disease resistance in aquatic organisms. Published research reports also demonstrated EOs effectiveness against Ichthyophthirius multifiliis, Gyrodactylus sp., Euclinostomum heterostomum, and other parasites both in vivo and in vitro. Moreover, different infectious fish pathogenic bacteria like Aeromonas salmonicida, Vibrio harveyi, and Streptococcus agalactiae destruction was confirmed by plant originated EOs. However, no research was conducted to confirm the mechanism of action or pathway identification of EOs to combat aquatic parasites and disease-causing microbes. This review aims to explore the effectiveness of EOs against fish parasites and pathogenic bacteria as an environment-friendly phytotherapeutic in the aquaculture industry. Moreover, research gaps and future approaches to use EOs for sustainable aquaculture practice are also postulated