Infection In Tilapia Research Articles

Immunoprotective Effect of Coptis chinensis-Supplemented Diet on Streptococcus agalactiae Infection in Tilapia

This study aimed to investigate the immunoprotective effect of Coptis chinensis (CC) on Streptococcus agalactiae (SA) infection in tilapia. Experimental fish were randomly divided into two groups feeding on a normal diet (ND) and a CC-supplemented diet (CCD) for 2 weeks and then injected with SA. After the inoculation experiment, the ND and CCD groups were named PI_ND and PI_CCD, respectively. CCD increased superoxide dismutase (SOD) activity and decreased malondialdehyde (MDA) activity significantly before and after infection. Immunological assays revealed that the serum interleukin-1β (IL-1β), complement 3 (C3), immunoglobulin M (IgM), Interferon-gamma (IFN-γ), and tumor necrosis factor-α (TNF-α) levels in the CCD group were significantly higher than in the ND group both before and after infection. In addition, proteomics analysis of liver tissue identified 62 differentially expressed proteins (DEPs) in CCD vs. ND, and 36 DEPs in the PI_CCD vs. the PI_ND groups. Furthermore, 80 specific upregulated proteins and 49 specific downregulated proteins were screened in the CCD group. The specific upregulated proteins included important antimicrobial enzymes such as lysozymes and cathepsin D, and antimicrobial peptides such as septins, granulin, and grancalcin, involving multiple KEGG brite categories such as enzymes, exosomes, membrane transport, and proteolipid proteins. Furthermore, specific downregulated proteins were enriched in glycolysis/gluconeogenesis and TCA cycle pathways. In conclusion, CC supplementation effectively enhances the ability of tilapia to resist SA infection by modulating various antioxidant enzymes, immune factors, antimicrobial enzymes, and antimicrobial peptides, and by moderately inhibiting central carbon metabolism. These findings provide a basis for replacing antibiotics with environmentally-friendly functional aquatic feeds to control bacterial diseases.

Enolase-based nanovaccine immersion immunization induces robust immunity and protection against Streptococcus infection in tilapia

Streptococcal disease is one of the most serious diseases in tilapia, causing huge economic losses to the tilapia farming industry. Streptococcus agalactiae (S. agalactiae) and Streptococcus iniae (S. iniae) are the two main pathogens of tilapia streptococcosis. Vaccination has been proved to be an effective measure to control fish bacterial diseases. In this study, we selected the Enolase (Eno) as the candidate vaccine antigen, which is the common antigen of S. agalactiae and S. iniae with high similarity (97.2%), the rEno was obtained and the CNT-rEno nanocarrier vaccine system was constructed by connecting the rEno protein with functionalized carbon nanotubes (CNTs), the immersion immune effect against S. agalactiae and S. iniae infection was evaluated. The results showed that, compared with the control group, CNT-rEno significantly enhanced the serum antibody production, related enzyme activities and immune-related genes expression. It was worth noting that CNT-rEno demonstrated better immunoprotection against S. agalactiae and S. iniae infection, with relative percent survivals of 73.68% (S. agalactiae) and 68.96% (S. iniae), respectively, which were both much higher than those of rEno groups (36.84% and 31.03%, respectively). Our study indicated that the CNT-rEno nanovaccine had the ability to elicit robust immune responses in tilapia by immersion immunization, and had the potential to offer cross-protection against S. agalactiae and S. iniae infection.

In vivo antibacterial activity of medicinal plant Sophora flavescens against Streptococcus agalactiae infection.

Streptococcosis disease caused by Streptococcus agalactiae (Group B Streptococcus, GBS) results in a huge economic loss of tilapia culture. It is urgent to find new antimicrobial agents against streptococcosis. In this study, 20 medicinal plants were evaluated in vitro and in vivo to obtain medicinal plants and potential bioactive compounds against GBS infection. The results showed that the ethanol extracts of 20 medicinal plants had low or no antibacterial properties in vitro, with a minimal inhibitory concentration ≥256 mg/L. Interestingly, in vivo tests showed that 7 medicinal plants could significantly inhibit GBS infection in tilapia, and Sophora flavescens (SF) had the strongest anti-GBS activity in tilapia, reaching 92.68%. SF could significantly reduce the bacterial loads of GBS in different tissues (liver, spleen and brain) of tilapia after treated with different tested concentrations (12.5, 25.0, 50.0 and 100.0 mg/kg) for 24 h. Moreover, 50 mg/kg SF could significantly improve the survival rate of GBS-infected tilapia by inhibiting GBS replication. Furthermore, the expression of antioxidant gene cat, immune-related gene c-type lysozyme and anti-inflammatory cytokine il-10 in liver tissue of GBS-infected tilapia significantly increased after treated with SF for 24 h. Meanwhile, SF significantly reduced the expression of immune-related gene myd88 and pro-inflammatory cytokines il-8 and il-1β in liver tissue of GBS-infected tilapia. The negative and positive models of UPLC-QE-MS, respectively, identified 27 and 57 components of SF. The major components of SF extract in the negative model were α, α-trehalose, DL-malic acid, D- (-)-fructose and xanthohumol, while in the positive model were oxymatrine, formononetin, (-)-maackiain and xanthohumol. Interestingly, oxymatrine and xanthohumol could significantly inhibit GBS infection in tilapia. Taken together, these results suggest that SF can inhibit GBS infection in tilapia, and it has potential for the development of anti-GBS agents.

Study on isolation and some pathological characteristics of Flavobacterium columnare causing infection in tilapia (Oreochromis spp.) cultured in Northern Vietnam

The study aims to isolate, identify, and determine the pathological characteristics of Flavobacteria columnarecausing disease in tilapia cultured in Northern Vietnam. A total of 138 samples of tilapia suspected of being infected with F. columnare were collected from 34 disease outbreaks at 21 tilapia farms in Hoa Binh, Ha Nam, and Hai Duong provinces. The results showed that infected tilapia exhibited typical symptoms such as fibrous, silver gills, appearance of silvery white spots on the skin, fibrous fins. The outbreaks can occurr in tilapia farms anytime, but focusing and much damage in the winter-spring crop with accumulative mortality rates from 5-35%. A total of 87 isolates were retrieved from the fish samples; 34 representative isolates (1 isolate per outbreak) were successfully identified by phenotypic, biochemical tests, and PCR assays. Using TYES medium, the F. columnare isolates grew in yellow and rhizoid colonies after 36-48 h of culture. The bacteria were gram-negative, long filamentous, absorbed Congo red dye, produced flexirubin pigment, gliding motility, and were positive to catalase and oxidase tests. F. columnare grew well at a temperature of 25-28°C, pH 7-8 and NaCl concentration below 5‰. The present results provide critical information in developing strategies for the prevention and control of F. columnare infection in tilapia.

Comparative study of the effects of Montanide™ ISA 763A VG and ISA 763B VG adjuvants on the immune response against Streptococcus agalactiae in Nile tilapia (Oreochromis niloticus)

Streptococcus agalactiae is regarded as a major bacterial pathogen of farmed fish, with outbreaks in Nile tilapia causing significant losses. Vaccination is considered the most suitable method for disease control in aquaculture, with the potential to prevent such outbreaks if highly efficacious vaccines are available for use. Several vaccines have been produced to protect against S. agalactiae infection in tilapia, including inactivated vaccines, live attenuated vaccines, and subunit vaccines, with variable levels of protection seen. Two commercial adjuvants, Montanide™ ISA 763A VG and ISA 763B VG, have been developed recently and designed to improve the safety and efficacy of oil-based emulsions delivered by intraperitoneal injection. In particular, their mode of action may help identify and stimulate particular immunological pathways linked to the intended protective response, which is an important tool for future vaccine development. Therefore, this study aimed to characterize the potential of two adjuvanted-bacterial vaccines against S. agalactiae (SAIV) comparatively, to determine their usefulness for improving protection and to analyse the immune mechanisms involved. Nile tilapia were divided into four groups: 1) fish injected with PBS as a control, 2) fish injected with the SAIV alone, 3) fish injected with the SAIV + Montanide™ ISA 763A VG, and 4) fish injected with the SAIV + Montanide™ ISA 763B VG. Following immunization selected innate immune parameters were analysed, including serum lysozyme, myeloperoxidase, and bactericidal activity, with significantly increased levels seen after immunization. Cytokines associated with innate and adaptive immunity were also studied, with expression levels of several genes showing significant up-regulation, indicating good induction of cell-mediated immune responses. Additionally, the specific IgM antibody response against S. agalactiae was determined and found to be significantly induced post-vaccination, with higher levels seen in the presence of the adjuvants. In comparison to the protection seen with the unadjuvanted vaccine (61.29% RPS), both Montanide™ ISA 763A VG and Montanide™ ISA 763B VG improved the RPS, to 77.42% and 74.19% respectively. In conclusion, Montanide™ ISA 763A VG and Montanide™ ISA 763B VG have shown potential for use as adjuvants for fish vaccines against streptococcosis, as evidenced by the enhanced immunoprotection seen when given in combination with the SAIV vaccine employed in this study.

Characterization and virulence of Streptococcus agalactiae deficient in SaeRS of the two-component system.

There are a variety of regulatory systems in bacteria, among which the two-component system (TCS) can sense external environmental changes and make a series of physiological and biochemical reactions, which is crucial for the life activities of bacteria. As a member of TCS, SaeRS is considered to be an important virulence factor in Staphylococcus aureus, but its function in tilapia (Oreochromis niloticus)-derived Streptococcus agalactiae remains unknown. To explore the role of SaeRS in regulating virulence in the two-component system (TCS) of S. agalactiae from tilapia, ΔSaeRS mutant strain and CΔSaeRS complementary strain were constructed by homologous recombination. The results showed that the abilities of growth and biofilm formation of ΔSaeRS strain were significantly decreased when cultured in a brain heart infusion (BHI) medium (P < 0.01). Also, the survival rate of the ΔSaeRS strain in blood was decreased when compared with the wild strain S. agalactiae THN0901. Under the higher infection dose, the accumulative mortality of tilapia caused by the ΔSaeRS strain was significantly decreased (23.3%), of which THN0901 and CΔSaeRS strains were 73.3%. The results of competition experiments in tilapia showed that the invasion and colonization abilities of the ΔSaeRS strain were also dramatically lower than those of the wild strain (P < 0.01). Compared with the THN0901, the mRNA expression levels of virulence factors (fbsB, sip, cylE, bca, etc.) in the ΔSaeRS strain were significantly down-regulated (P < 0.01). SaeRS is one of the virulence factors of S. agalactiae. It plays a role in promoting host colonization and achieving immune evasion during the infection of tilapia, which provides a basis for exploring the pathogenic mechanism of S. agalactiae infected with tilapia.

Significant alterations of intestinal symbiotic microbiota induced by intraperitoneal vaccination mediate changes in intestinal metabolism of NEW Genetically Improved Farmed Tilapia (NEW GIFT, Oreochromis niloticus)

BackgroundAfter millions of years of coevolution, symbiotic microbiota has become an integral part of the host and plays an important role in host immunity, metabolism, and health. Vaccination, as an effective means of preventing infectious diseases, has been playing a vital role in the prevention and control of human and animal diseases for decades. However, so far, minimal is known about the effect of vaccination on fish symbiotic microbiota, especially mucosal microbiota, and its correlation with intestinal metabolism remains unclear.MethodsHere we reported the effect of an inactivated bivalent Aeromonas hydrophila/Aeromonas veronii vaccine on the symbiotic microbiota and its correlation with the intestinal metabolism of farmed adult Nile tilapia (Oreochromis niloticus) by 16S rRNA gene high-throughput sequencing and gas chromatography-mass spectrometry metabolomics.ResultsResults showed that vaccination significantly changed the structure, composition, and predictive function of intestinal mucosal microbiota but did not significantly affect the symbiotic microbiota of other sites including gill mucosae, stomach contents, and stomach mucosae. Moreover, vaccination significantly reduced the relative abundance values of potential opportunistic pathogens such as Aeromonas, Escherichia–Shigella, and Acinetobacter in intestinal mucosae. Combined with the enhancement of immune function after vaccination, inactivated bivalent Aeromonas vaccination had a protective effect against the intestinal pathogen infection of tilapia. In addition, the metabolite differential analysis showed that vaccination significantly increased the concentrations of carbohydrate-related metabolites such as lactic acid, succinic acid, and gluconic acid but significantly decreased the concentrations of multiple lipid-related metabolites in tilapia intestines. Vaccination affected the intestinal metabolism of tilapia, which was further verified by the predictive function of intestinal microbiota. Furthermore, the correlation analyses showed that most of the intestinal differential microorganisms were significantly correlated with intestinal differential metabolites after vaccination, confirming that the effect of vaccination on intestinal metabolism was closely related to the intestinal microbiota.ConclusionsIn conclusion, this paper revealed the microbial and metabolic responses induced by inactivated vaccination, suggesting that intestinal microbiota might mediate the effect of vaccination on the intestinal metabolism of tilapia. It expanded the novel understanding of vaccine protective mechanisms from microbial and metabolic perspectives, providing important implications for the potential influence of vaccination on human intestinal microbiota and metabolism.-tufGxbkxhm-UiFTxxYHNiVideo

Transcriptome Analysis of Immune Response against Streptococcus agalactiae Infection in the Nile Tilapia GIFT Strain

Streptococcus agalactiae (group B streptococcus, GBS), a broad-spectrum pathogen, causes great economic losses in fish aquaculture, especially the industry of tilapia. Until now, the knowledge of the immune response mechanism against S. agalactiae infection in tilapia has been limited. In the present study, the gill transcriptome of the tilapia from the GBS and the phosphate buffered saline (PBS) groups were sequenced. The transcriptomic analysis results presented the differentially expressed genes (DEGs) at different time points (DEGs number, 6 h: 2122, 9 h: 1851, 15 h: 1791, and 18 h: 2395) after GBS injection, and significantly enriched immune-related gene ontology (GO) terms such as the innate immune response. The significantly enriched immune pathways included the Toll-like receptor signaling pathway, the nucleotide oligomerization domain (NOD)-like receptor signaling pathway, the cytosolic-DNA sensing pathway, and the intestinal immune network for Immunoglobulin A (IgA) production. Most of the DEGs in Toll-like receptor signaling, NOD-like receptor signaling, and cytosolic-DNA sensing pathways presented upregulations at 18 h, which indicated that the innate immune pathways were activated. Two immune-related pathways (phagosome and cell adhesion molecules) were significantly enriched at all time points, suggesting that these two pathways might also play important roles in the immune response against the GBS infection. The results of HE staining showed that the gills of tilapia were damaged seriously at 9 h post-infection, which might be due to the possibility of pyroptosis resulting from the changes of DEGs in the NOD-like receptor signaling pathway. This study provided new insight into the mechanisms of gill damage in fish infected with S. agalactiae.

Pengaruh Pemberian Ekstrak Anggur laut (Caulerpa racemosa) Dalam Menghambat Infeksi Bakteri Aeromonas hydrophila Pada Ikan Nila (Oreochromis niloticus)

This study aims to determine the effect of giving sea grape extract (Caulerpa racemosa) in inhibiting Aeromonas hydrophila bacterial infection in tilapia (Oreochromis niloticus) and to determine the concentration of use of sea grape (Caulerpa racemosa) which is effective to inhibit Aeromonas hydrophila bacterial infection in tilapia (Oreochromis niloticus) and this study was an experimental study using a completely randomized design (CRD).The variables observed in this study were changes in fish behavior, fish morphology, fish anatomy, survival, water quality parameters (temperature, DO, pH). The data was processed using the SPSS Version 24 program with Analysis (ANOVA) if there were differences, then continued with Duncan.The results showed that the administration of sea grape extract (Caulerpa racemosa) could inhibit Aeromonas hydrophila bacterial infection in tilapia. The average level of inhibitory power of the extract was the best in treatment C with 25 mg/l of sea grape extract (Caulerpa racemosa) the condition of the fish improved on day 1 postoperatively. immersion and the lowest level of inhibition in the control treatment the condition of the fish was getting worse every day, having a significant effect (P&lt;0.05), the highest survival was in treatment C where survival on day 14 was 73%. Water quality average temperature 27% C, average dissolved oxygen 5-6 ppm and average pH 7.4-7.8

Pengaruh Asap Cair Tempurung Kelapa (Cocos nucifera) terhadap Hematologi Ikan Nila (Oreochromis niloticus) yang Diuji Tantang Bakteri Aeromonas hydrophila

Aeromonas hydrophila adalah penyakit bakteri pathogen yang berperan penting dalam menyebabkan kematian pada komoditas ikan nila. Pada penelitian ini, pakan yang mengandung asap cair tempurung kelapa yang dapat diaplikasikan sebagai imunostimulan untuk mengobati penyakit Motile Aeromonad Sepricemia (MAS) pada ikan Nila. Penelitian ini bertujuan untuk mengetahui pengaruh asap cair tempurung kelapa pada uji aktivitas antibakteri secara In vitro dan uji tantang A. hydrophyla secara uji In vivo. Tahapan uji invitro meliputi uji MIC, uji sensitivitas asap cair, dan antibiotik ampicillin sebagai kontrol. Selanjutnya pada uji invivo dengan mencampurkan setiap 100gr pakan yang mengandung asap cair dengan dosis 1%, 3%, 5%, 7% dan 9% (v/w). Selanjutnya uji tantang tantang dilakukan dengan menyuntikan suspensi bakteri A. hydrophila dengan dosis 106 sel/cfu sebanyak 0,1 ml secara oral pada pakan dan variabel pengamatan meliputi total eritrosit, hemoglobin, kadar hematokrit dan gejala klinis ikan nila. Analisis data menggunakan Anova dan diuji DMRT dengan selang kepercayaan 95%. Hasil penelitian menunjukan bahwa konsentrasi asap cair terbaik secara invitro dengan MIC 1% dan sensitivitas asap cair 9% dengan diameter 5.63 cm, sedangkan uji tantang yang paling efektif pada perlakuan 3% dapat menurunkan infeksi A. hydrophyla pada ikan nila dengan jumlah total eritrosit (106/L): 2,27±0,15, total hemoglobin (g/dL): 8,03±0,21, dan kadar hematokrit (%): 21,35±1.34 (p &lt; 0.05). Ikan nila yang diuji tantang dengan A. hydrophila pada perlakuan kontrol menunjukkan gejala sirip geripis, sisik mengelupas, hemoragic, dan exopthalmia. Sedangkan perlakuan yang diberikan asap cair melalui pakan menunjukan kondisi ikan nila lebih baik pada gejala klinis dan analisis hematologi daripada ikan yang tidak diberikan perlakuan.

Examination of virulence and the effects of environmental conditions on the growth of Aeromonas hydrophila in farmed tilapia and histopathological changes in infected fish

The study aims to examine the pathogenicity, the effects of environmental conditions on the growth of Aeromonas hydrophila in tilapia, and histopathological changes in infected fish. A. hydrophila isolates, which were recovered from diseased tilapia samples collected at farming cages/ponds in several northern Vietnam provinces, were identified by biochemical tests, PCR confirmation, and sequencing of 16S rRNA and housekeeping genes (gyrB). Three representative strains after identification were subjected to evaluate the pathogenicity via challenge experiments using the intraperitoneal injection method and to determine the impacts of environmental factors on their growth. The present study showed an average LD50 value (lethal dose 50%) of A. hydrophila to tilapia at 4.6×105 CFU/fish, the infected fish in the challenge tests presented the clinical and gross lesions similar to the natural diseased fish, including haemorrhaging at the base of fins, skin, anal opening and in visceral organs, especially in liver and intestine. Histopathological examination of the diseased fish showed the hyperplasia of epithelial cells and haemorrhage of the gill filaments. The tissues of the liver, kidney, and spleen exhibited the lesion of haemorrhage, congestion, and degeneration, while the brain tissue appeared the colonisation by the bacteria. The A. hydrophila strains from tilapia showed a high tolerance to environmental conditions with the capacity to survive and multiply at a temperature of 15-45°C, a salinity of 0-60‰ and a pH of 5-10. The present results provide useful information to establish the strategies in prevention of A. hydrophila infection in tilapia and other freshwater fish.

Pharmacokinetics and pharmacokinetic/pharmacodynamic-based dosing regimens of long-acting oxytetracycline in Nile tilapia (Oreochromis niloticus) broodstock to minimize selection of drug resistance

This study aimed to determine the pharmacokinetics of long-acting oxytetracycline (OTC-LA) after intraperitoneal (IP) administration in Nile tilapia broodstock. Pharmacokinetic/pharmacodynamic (PK/PD) relationships were evaluated to determine the optimal dosing regimens of OTC-LA against Streptococcus agalactiae. A total of 120 healthy male tilapia (450 ± 37.47 g) were arbitrarily divided into two groups (60 fish/group) that individually received OTC-LA single IP injection at dosages of 50 or 100 mg/kg body weight. Blood samples were collected at various times posttreatment, and plasma oxytetracycline (OTC) was analyzed using high-performance liquid chromatography. For pharmacodynamic study, 56 S. agalactiae isolates were subjected to agar dilution to determine the minimum inhibitory concentration (MIC) and mutant prevention concentration (MPC). Results showed that the Cmax and Tmax of OTC-LA were both 110.70 ± 5.61 μg/mL at 2 h for the dosage of 50 mg/kg and 287.85 ± 8.03 μg/mL at 4 h for the dosage of 100 mg/kg. Plasma OTC levels remained at 3.99 ± 0.48 and 23.00 ± 2.51 μg/mL at 168 h (7 day) after OTC-LA administration at 50 and 100 mg/kg, respectively. The MIC50 and MIC90 of S. agalactiae were 0.5 and 1 μg/mL, respectively, and its MPC50 and MPC90 were 32 and 128 μg/mL, respectively. The mutant selection window of MIC50 and MPC50 was 0.5–32 μg/mL, and that of MIC90 and MPC90 was 1–128 μg/mL. OTC-LA at 50 and 100 mg/kg provided plasma OTC levels above MIC for at least 7 days. However, only OTC-LA at 100 mg/kg can provide plasma OTC to prevent the growth of resistant mutant subpopulation. Our study suggested that a single IP administration of OTC-LA at 100 mg/kg body weight is the optimal dosing regimen to attain therapeutic efficacy against S. agalactiae infection in tilapia and prevent the emergence of resistant mutant subpopulation.

Identification of Ectoparasite Infection in Tilapia (Oreochromis niloticus) Based on Water Quality in Rawa Pening

Testing of ectoparasites on water quality in infections that occured in tilapia in aquaculture activities in Rawa Pening. The purpose of this study was to determine the exposure to the abundance of ectoparasite bacteria that infected the growth of tilapia in Rawa Pening. This study used experimental method and purposive sampling with data processing in a descriptive survey. The data analysis used was analysis of variance (ANOVA) with the aim of knowing the effect of sampling and the parameters tested, this test was carried out 4 (four) times for water quality and ectoparasite observations 3 (three) times for testing to obtain the accuracy of data sampling. The results of this study showed that there was an infection with levels of ectoparasites identified from the types of Streptococcus sp, Lernaea sp, Aeromonas sp, and Trichodina sp. These bacteria attack fish with the highest number or total exposure in the Tuntang area. The reason was, currently water hyacinth was being cut down as one of the local government programs to reduce the blooming of water hyacinth (Eichhornia crassipes) of 7.92 mg/L, pH levels 7.59, ammonia levels 10-20 mg/L and nitrate levels 0.5 mg/L were still in optimal conditions from the results carried out.

VIRULENCE GENE PROFILING AND PATHOGENICITY OF Streptococcus agalactiae ISOLATED FROM TILAPIA, Oreochromis niloticus FARMS IN INDONESIA

Streptococcosis caused by Streptococcus agalactiae has become a major disease problem in tilapia culture in Indonesia. This study aimed to detect virulence genes of S. agalactiae during streptococcosis disease outbreaks in several tilapia farms in Indonesia and evaluate the correlation between biotype and virulence genes to bacterial virulence. The presence of virulence genes was determined in 10 strains of S. agalactiae isolated from farm-raised tilapia. Polymerase chain reaction (PCR) protocol was used to determine genes for cylE, hylB, lmb, bib A, PI-2b, fbs A, fbs B, gap, PI-1, and cfb in the template DNA. Pathogenicity test was carried out by intraperitoneal injection of 24 hour-cultured S. agalactiae to tilapia with 108 CFU/fish. Four isolates have seven of virulence genes (cylE, hylB, bibA, PI-2b, fbs A, fbs B, and gap genes), three isolates have six virulence genes (hylB, bib A, fbs A, fbs B, gap, cfb genes), one isolate has four virulence gene (hyl B, bib A, fbs, and cfb genes), and one isolate has one virulence gene (PI-2b gene). None of the isolates has lmb or PI-1 genes. Bacteria with more virulence genes showed higher pathogenicity post injection. Mortality of tilapia injected with b-hemolytic bacteria was 100% within the period of 14-19 hours, while non-hemolytic bacteria was 53.3%-86.6% on 14 days post-injection. Pathological changes associated with the infection by either isolate included melanosis, slow response, anorexia, ocular opacity, gasping, erratic, C-shape, and whirling. It can be concluded that S. agalactiae with more virulence genes show a higher level of pathogenicity. The presence of a virulent gene has the potential to be used as a basis for selecting candidate isolates and designing vaccine compositions as an effort to prevent streptococcosis infection in tilapia in Indonesia.

Seaweed polysaccharide mediated synthesis of silver nanoparticles and its enhanced disease resistance in Oreochromis mossambicus

ObjectivePreliminary aim of this research work focuses on testing the efficacy of silver nanoparticles synthesised using water soluble polysaccharides extracted from seaweeds against pathogenic fish bacteria. The emergence of various virulence pathogens during the culturing period leads to mass mortality and influence the loss of aquaculture production. MethodsThe intervention of nanotechnology in the field of aquaculture improves the growth and immunity of aquatic animals when the part of nanomaterials mixed with fish feed. Sometimes the green synthesis of silver nanoparticles prepared from the seaweed polysaccharide play a vital role in the disease controlling strategies in aquaculture farming. The nanoparticle formation and confirmation was charecterized by Ultra Visible Spectroscopy (UV–Vis), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscope (SEM), Dynamic Light Scattering (DLS). Results and ConclusionBiologically synthesized silver nanoparticles have been used as an alternative method for commercial antibiotics to control such pathogenic infection with 70–80% of survival rate. Polysaccharides of Caulerpa racemosa was used as a reducing agent in this present study. Particularly the phytochemicals are involved in the silver salt reduction process. Total polyphenol, total flavonoids, total antioxidant, hydroxyl radical scavenging assay and DPPH was found to be 12.32 mg/g, 18.44 mg/g, 38.12 mg/g equivalence, 82.2% and 49.05% respectively. Biologically synthesised AgNps capable of preventing the Pseudomonas aeruginosa infection in tilapia, it was proved by in vitro and in vivo antibacterial activities. Present study provided the ample achievement and these findings found to be effective in controlling the Pseudomonas infection in tilapia fishes.

Assessment the efficacy of some various treatment methods, in vitro and in vivo, against Aeromonas hydrophila infection in fish with regard to side effects and residues

Aeromonas hydrophila is an opportunistic bacteria with an overwhelming impact on fish farming industry especially with upraising of drug resistant mutants. This study aimed to evaluate and compare the therapeutic and side effects of levofloxacin (LEV), chitosan-nanoparticles (CNPs), and fructooligosaccharides (FOS) in control of this infection in tilapia. A total of 160 Nile-tilapia divided into 8-groups; G1: negative-control, G2: infected-control, G3: non-infected-(levofloxacin (LEV) 10 mg/kg bwt), G4: non-infected-(chitosan-nanoparticles (CNPs) 1 g/kg ration), G5: non-infected-(fructooligosaccharides (FOS) 20 g/kg ration), G6: infected-LEV, G7: infected-CNPs and G8: infected-FOS for 7 days. MICs were (0.125 μg/ml and 1.25 mg/ml) for LEV and CNPs respectively. No mortalities or significant adverse effects were recorded in non-infected treated-groups while infected were (20%) LEV, (30%) CNPs, (40%) FOS and (70%) G2. Aspartate aminotransferase (AST), alanine aminotransferase (ALT) and alkaline phosphatase (ALP) decreased by LEV and CNPs than FOS while all increased total protein (TP) and albumin than G2. Malondialdehyde (MDA) significantly decreased and superoxide dismutase (SOD) and reduced glutathione (GSH) increased in all infected-treated groups than G2 in various degrees. Urea and creatinine descending order were FOS, LEV then CNPs decreased significantly than G2. LEV musculature residues, using HPLC, decreased gradually till the 5th day; 621.00 ± 0.66, 270.00 ± 0.48 then 64.00 ± 0.40, and 471.00 ± 0.79, 175.00 ± 0.52 ppb then not detected at 1st, 3rd, and 5th days of withdrawal in non-infected and infected groups respectively. Finally, LEV and CNPs were superior as bactericidal, decreasing mortalities and enzyme activities while CNPs and FOS increased performance, non-specific immunity, and antioxidant biomarkers.

Standardization of Dose and Delivery of Oxytetracycline against Streptococcus agalactiae Infection in Genetically Improved Farmed Tilapia (GIFT)

Background: Tilapia (Oreochromis niloticus) is one of the most important aquaculture species in India. Streptococcus agalactiae is a highly debilitating pathogen of farmed tilapia. In this study, oxytetracycline (OTC) dose and delivery were standardized against S. agalactiae infection in genetically improved farmed tilapia (GIFT) and pharmacokinetics after oral administration was evaluated. Methods: LD50 value of S. agalactiae was found to be 6.2×106 CFU/fish. Two methods of drug delivery were investigated at three different doses of 50, 70 and 90 mg/kg against the S. agalactiae infection. Pharmacokinetics of OTC was studied after per os administration of 100 mg/kg body weight per day and analysing the residues in kidney, liver and muscle at different time intervals. Result: Per os delivery of OTC 90 mg/kg controlled S. agalactiae infection and the withdrawal time of OTC to fall below MRL of 0.05 µg/g at 30°C was 21 days in kidney and liver and 14 days in muscle. The study indicated that the S. agalactiae infection in tilapia could be controlled by OTC and fish can be marketed after providing a withdrawal period of 14 days.

Anthelmintic‐like Activity of Leucaena leucocephala Aqueous Extract Against Gyrodactylus spp. in Naturally Infected Tilapia Fingerlings

AbstractAquaculture represents the fastest growing food‐producing sector worldwide. However, the intensification of fish farms has led to environmental, health, and welfare challenges. The monogenean ectoparasite Gyrodactylus spp. has been considered one of the most pathogenic ectoparasites affecting fish, and no specific control strategies besides formalin baths have been established. The use of bioactive plants has been recently proposed as an alternative method to control gyrodactylid infections. Leucaena leucocephala is a tropical legume that has been found with anthelmintic activity against both internal and external parasites of cattle. Therefore, the objective of this study was to assess the anthelmintic‐like activity of L. leucocephala aqueous extract against Gyrodactylus spp. in hybrid tilapia Oreochromis spp. fingerlings and its effect on host health through histopathological analysis. Five concentrations of L. leucocephala aqueous extract were employed (2.00, 1.00, 0.50, 0.25, and 0.125 mg/mL) to estimate the mean effective concentration (EC50). Distilled water and formalin (1:4,000) were used as negative and positive controls, respectively. The aqueous extract of L. leucocephala showed a dose‐dependent behavior, with an EC50 of 0.228 mg/mL. Quercetin was identified as the main phytochemical present in the extract. Postmortem analysis of fingerlings exposed to the plant extract had no treatment‐associated pathological findings, thus indicating that the use of L. leucocephala baths had no negative impact that could jeopardize the lives of treated animals. After the in vivo assessment, the aqueous extract of L. leucocephala appears to be a promising alternative to control gyrodactylid infection in tilapia.

Implementation of ghost vaccine against the Streptococcus agalactiae infection in Tilapia

Streptococcus agalactiae(S. agalactiae), a gram-positive bacteria, can cause infections in an extensive range in fish, humans, and some other animals. This study realized the non-living, empty cell enveloped Bacterial ghosts (BGs) were incredibly

Transcriptome analysis of immune- and iron-related genes after Francisella noatunensis subsp. orientalis infection in Nile tilapia (Oreochromis niloticus)

Francisella noatunensis subsp. orientalis (Fno) is a gram-negative intracellular bacterium identified in many fish species worldwide, including cultured Nile tilapia (Oreochromis niloticus) in Taiwan. To investigate the gene expression responses to Fno infection, we performed transcriptome analysis of the head kidney and spleen in Nile tilapia using RNA-seq. Total RNA was extracted from the head kidney and spleen of infected (Fno-injected) and uninfected (control) tilapia at 1-day and 2-days post-infection, and RNA-seq was performed using the Illumina HiSeq™ 4000 platform. After de novo assembly, a total of 106,534 transcripts were detected. These transcripts were annotated and categorized into a total of 7171 genes based on the KEGG pathway database. Differentially expressed genes (DEGs) were significantly (2-fold difference comparing Fno and PBS groups at each time point) enriched in the immune-related pathways, including the following: complement and coagulation cascades, cytokine-cytokine receptor interaction, hematopoietic cell lineage, lysosome, phagosome. We identified the upregulation of inflammatory cytokine-, apoptosis-, and neutrophil-related genes, and downregulation of complement- and lymphocyte-related genes. Additionally, we found the induction of natural resistance-associated macrophage protein 1 (NRAMP1) and heme responsive gene-1 (HRG1). Anemia of inflammation, caused by intracellular iron storage in spleen after Fno infection, was also observed. This study provides natural disease control strategies against Fno infection in tilapia. It is suggested that intercellular iron storage is a host protection strategy.