Pathogenic Bacteria In Fish Research Articles

Phyllosphere bacteria with antiquorum sensing and antibiofilm activities against fish pathogenic bacteria

ObjectiveThis research aims to quantify antiquorum sensing and antibiofilm activity of f phyllosphere bacteria against biofilm formed by pathogenic fish bacteria such as Aeromonas hydrophila, Streptococcus agalactiae, and Vibrio harveyi.ResultsAntiquorum sensing assay using Chromobacter violaceum as indicator bacteria and antibiofilm assay showed six phyllosphere bacteria have antiquorum sensing and antibiofilm activities against tested bacteria. The highest inhibition and destruction activity was showed by metabolite of JB 3B and EJB 5 F against A. hydrophila, respectively. Determination using light microscope and scanning electron microscope performed decreaing in biomass of biofilm observed after treated with metabolite from phyllosphere bacteria.

The activity of Pometia pinnata leaf extract against pathogenic bacteria in fish

The use of antibiotics to cure bacterial diseases has a negative impact on fish and the environment, so it is necessary to look for natural products that are safe for treating fish diseases. This study aims to determine the activity of P. pinnata extract as an antibacterial towards V. alginolyticus, P. aeruginosa, A. salmonicida, E. ictaluri, A. hydrophila, and E. tarda bacteria. P. pinnata extract was obtained by maceration using ethanol solvent. This extract was tested for its phytochemical content, characterized by FT-IR and tested for its antibacterial activity by the agar diffusion method. The results of the phytochemical test of P. pinnata extract produced terpenoids compounds flavonoids, saponins and phenolic. The results of the FT-IR characterization of P. pinnata extract contained O-H, C-H, C=O and C-O groups. The results of the inhibition test showed that P. pinnata extract was able to inhibit the growth of V. alginolyticus bacteria by 13.0 mm to 14.7 mm. P. aeruginosa 14.5 mm to 17.1 mm. A. salmonicida by 12.4 mm to 14.9 mm. E. ictaluri by 13.5 mm to 15.5 mm. A. hydrophila 13.9 mm to 17.1 mm. E. tarda 13.6 mm to 15.5 mm. In conclusion, P. pinnata extract can be used to inhibit the growth of pathogenic bacteria in fish.

Antibacterial efficacy of Clidemia hirta leaf extract against pathogenic fish bacteria

Bacterial diseases pose a serious threat to aquatic ecosystems, and the use of antibiotics to address these problems can have harmful effects on both fish and their environment. Therefore, there is an increasing demand for safe natural alternatives to treat fish diseases. This research investigates the antibacterial properties of an extract from Clidemia hirta against various bacterial strains, including A. salmonicida, P. aeruginosa, E. ictaluri, A. hydrophila, V. alginolyticus, and E. tarda. Phytochemical analysis of the extract identified the presence of phenolic compounds, terpenoids, saponins, and flavonoids. The antibacterial effectiveness of the C. hirta extract was assessed using the agar diffusion method at concentrations of 50, 100, 150, 200, and 250 mg/mL. The findings indicated that the extract significantly inhibited the growth of A. salmonicida (16.5 mm to 23.3 mm), P. aeruginosa (17.3 mm to 23.5 mm), E. ictaluri (15.3 mm to 23.5 mm), A. hydrophila (15.3 mm to 21.8 mm), V. alginolyticus (16.8 mm to 22.8 mm), and E. tarda (15.0 mm to 22.8 mm). In summary, the extract from C. hirta shows potential as a natural agent to control pathogenic bacteria affecting fish.

Green and red macroalgae extracts show antibacterial effects and induce innate immune responses in Nile tilapia and rainbow trout in vitro

Green macroalgae (Ulva sp.) and red macroalgae (Solieria sp.) were processed to produce eight different crude extracts enriched for marine sulphated polysaccharides (MSP). While all extracts showed direct anti-bacterial effects to some degree, two red algal extracts, in particular, showed high activity against several pathogenic fish bacteria in vitro. Stimulation of head kidney leukocytes (HKLs) in vitro with MSP-rich extracts showed fish species specific differences. In Nile tilapia, HKLs showed a dose dependent production of reactive oxygen species (ROS) following stimulation with Ulva-derived extracts, while stimulation with Solieria-derived extracts did not induce ROS production. In rainbow trout, HKLs showed relatively high reactive ROS potential and Solieria-derived extracts could induce significant ROS production, albeit without a clear dose dependent response. Gene expression of in vitro stimulated HKLs showed a clear induction of most cytokines measured (il1b, il10, tnfa, ifny, il12p40), with differences between species. Although cytokine gene expressions were more prominently induced in HKLs of Nile tilapia than in HKLs of rainbow trout, immunomodulatory effects of both, Ulva- and Solieria-derived extracts, always appeared evident. It is likely that HKLs have the ability to sense presence of MSP, via so far uncharacterized pattern recognition receptors which have known downstream signalling pathways. Expression of some genes associated with Toll-like Receptor (TLR) signalling, such as irak1 and especially the expression of genes associated with C-type Lectin Receptor (CLR) signalling, such as card9 and bcl10 were evident following stimulation with MSP-rich extracts. Possibly, immunomodulatory effects of MSP could be regulated by at least a CLR-mediated signalling, at least in Nile tilapia, for which most if not all red algae and green algae extracts induced changes in gene expression of card9 and bcl10. Overall, induction of ROS production and gene expression read-outs suggest immunomodulatory effects of MSP-rich extracts derived from green algae (Ulva sp.) and red algae (Solieria sp.), at least in vitro. The observed effects suggest clear fish species specific differences between the effects of MSP-rich extracts.

Molecular cloning of the hepcidin gene from crescent sweetlips (Plectorhinchus cinctus) and characterization of its encoded antimicrobial peptide

Hepcidin has been identified as an important antimicrobial peptide exerting important innate immunomodulatory activities in many fish species. In the present study, reverse transcription PCR coupled with the rapid amplification of cDNA ends was used to obtain the full-length cDNA of the crescent sweetlips hepcidin gene, which is 829 bp in length and includes an 273 bp ORF encoding a peptide with 90 amino acid residues. Sequence alignment showed a typical RXKR motif and eight conserved cysteine residues in the deduced amino acid sequences. Four disulfide bonds were predicted to form between these eight cysteines, which may stabilize the hairpin structure in hepcidin molecule. Furthermore, phylogenetic analysis showed that the deduced amino acid sequences of crescent sweetlips hepcidin had high sequence homology to hepcidins from fish species of Eupercaria. In addition, the crescent sweetlips hepcidin peptide demonstrated a strong antimicrobial activity in vitro against several types of pathogenic bacteria in fish. In conclusion, the obtained results suggested that crescent sweetlips hepcidin possessed the typical structure similar to other fish hepcidins and had strong antibacterial activity, which showed great potential in the prevention of fish diseases in aquaculture.

Effect of Galangal (Alpinia galanga L.) Rhizome for the Health of Cultured Fish

For fish farmers, the disease are the biggest cause of loss. In an effort to control the disease is often done by using synthetic antibiotics. The continuous use of synthetic antibiotics with uncontrolled doses can lead to resistance of pathogenic microbes to these antibiotics, accumulation of antibiotics in the aquatic environment and fish bodies which is certainly dangerous for human health and other aquatic biota. The use of herbal ingredients is the right strategy for disease control in fish, because it is relatively safer and cheaper. Medicinal ingredients derived from plants have been used for thousands of years as traditional medicine by people in various parts of the world. This traditional medicine is widely used by the community not only for treatment (curative), but also as an alternative to prevent disease, to rehabilitation and also to increase immunity and health. Galangal rhizome contains several chemical compounds, namely phenols/tannins, quinones, steroids/triterpenoids, flavonoids. Based on the phytochemical content, galangal rhizome has several pharmacological property that are useful for human health, namely as antibacterial, anti-fungal, anti-inflammatory, anti-hepatotoxic, antioxidant, immunostimulant, anti-ulcerative, anti-tumor, and anti-allergenic activities. In addition, galangal (Alpinia galanga L.) rhizomes can improve growth and feed efficiency. The purpose of this article is to describe the extent to which galangal rhizomes can be used to maintain the health of cultured fish. Based on the previou studies, galangal rhizome is potential and effective for maintaining fish health, because the antibacterial properties of legkuas rhizome can treat several species of cultured fish Cyprinus carpio, Oreochromis niloticusand Clarias gariepinus which are infected with the pathogenic bacteria Aeromonas hydrophilla. In vitro test results of galangal rhizome are bacteriostatic against pathogenic bacteria in fish, namely Edwardsiella tarda. The antifungal properties of galangal rhizomes can treat Oreochromis niloticus, Kryptoterus bicirrhis, Osphronemus gouramy and Borbonymus gonionotus infested with fungus Saprolegnia sp. As an immunostimulant, galangal rhizome is able to prevent eggs and fry of C. gariepinus from being attacked by Saprolegniasp, Pseudomnas sp. and A. hydrophilla.

Effect of The Combination of Kefa Forest Honey and Euphorbia hirta as a Curative agent of Vibrio alginolyticus in the Hybrid Grouper Epinephelus fuscoguttatus

Kefa forest honey and Euphorbia hirta have an antibacterial effect against pathogenic bacteria in fish. This work investigated the combination of honey and E. hirta against Vibrio alginolitycus in the hybrid grouper Epinephelus fuscoguttatus. The active ingredients and antibacterial activity of Kefa forest honey and E. hirta were tested in vitro at different concentrations using the disk method. The experimental animals were injected with V. alginolitycus suspension at a concentration of 106 cells ml−1/fish. After the fish showed symptoms of infection, the treatment was carried out for 5 consecutive days by immersion in the mixture of 25% Kefa honey and E. hirta at different concentrations of honey and E. hirta combinations. After treatment, the fish were monitored for 7 days. During the study, observations on hematology and clinical symptoms were made. The results showed that the combination of Kefa honey and E. hirta had antibacterial activity against V. alginolitycus in vitro and in vivo can increase the hematological profile of grouper and alleviate clinical symptoms due to V. alginolitycus infection. The results showed that administration of a combination Kefa forest honey and E. hirta was effective as a cure for V. alginolyticus infection in grouper.

Lactiplantibacillus argentoratensis and Candida tropicalis Isolated from the Gastrointestinal Tract of Fish Exhibited Inhibitory Effects against Pathogenic Bacteria of Nile Tilapia

Nile tilapia is one of the most consumed farmed fish in the world. The outbreak of pathogenic bacterial diseases causes high mortality rates and economic losses in Nile tilapia farming. Antibiotic administrations are commonly utilized to inhibit and prevent bacterial infections. However, antibiotics are expensive and cause serious concerns for antibiotic resistance in fish that can be potentially transferred to humans. As an alternative solution, probiotics can be used to prevent infection of pathogenic bacteria in fish. In this work, both bacteria and yeast were isolated from fish gastrointestinal tracts and their inhibitory activity against Nile tilapia pathogenic bacteria was evaluated, as well as other probiotic properties. In this study, 66 bacteria and 176 acid tolerant yeasts were isolated from fish gastrointestinal tracts. Of all isolated microorganisms, 39 bacterial and 15 yeast isolates with inhibitory effect against pathogens were then examined for their probiotic properties (acidic and bile salt resistance, adhesion potential, and biofilm formation), formation of antibacterial factor survival rate under simulated gastrointestinal fluid, and safety evaluation. AT8/5 bacterial isolate demonstrated probiotic properties and the highest inhibition against all 54 tested pathogens while YON3/2 yeast isolate outperformed the inhibitory effect among all yeast isolates. These two probiotic isolates were further identified by 16S rDNA and the D1/D2 domain of 26S rDNA sequence analysis for bacterial and yeast identification, respectively. AT8/5 and YON3/2 showed the highest similarity to Lactiplantibacillus argentoratensis and Candida tropicalis, respectively. This is the first report on isolated L. argentoratensis and C. tropicalis with antipathogenic bacteria of Nile tilapia properties. Collectively, AT8/5 and YON3/2 could be potentially used as promising alternatives to existing antibiotic methods to prevent pathogenic bacteria infection in Nile tilapia farming.

Antibacterial activity of ethanol extract of banana, cassava, and pineapple peels against a fish pathogen Aeromonas hydrophila

Abstract. Mulia DS, Raicha R, Lunggani CP, Erina SN, Wuliandari JR, Purbomartono C, Isnansetyo A. 2023. Antibacterial activity of ethanol extract of banana, cassava, and pineapple peels against a fish pathogen Aeromonas hydrophila. Biodiversitas 24: 481-485. Aeromonas hydrophila is the most virulent bacteria for almost all freshwater fish species. One method to control pathogenic bacteria in fish should be safe and environmentally friendly, including utilizing natural wastes such as banana peels (Musa paradisiaca), cassava peels (Manihot esculenta), and pineapple peels (Ananas comosus). These natural wastes contain bioactive compounds. Their utilization increases the waste value. This study aims to determine the potential of banana peel, cassava peel, and pineapple peel waste as an antibacterial against A. hydrophila, a causing agent of Motile Aeromonas Septicemia (MAS) in freshwater fish. Parameters observed included phytochemical compounds, MIC, and MBC values of banana, cassava, and pineapple peels. Phytochemical screening was performed using thin-layer chromatography (TLC) and foam test. The microdilution method carried out the antibacterial activity of banana peel, cassava peel, and pineapple peel against A. hydrophila. It determines the minimum inhibitory concentration (MIC); and the minimum bactericidal concentration (MBC) values. Phytochemical screening results showed that banana, cassava, and pineapple peel extracts contained flavonoids, alkaloids, terpenoids, tannins, and saponins. The MIC values of banana peel, cassava peel, and pineapple peel extract were 600, 400, and 200 µg/mL, respectively. The MBC values of banana peel, cassava peel, and pineapple peels were 4 × MIC, 2 × MIC, and 1 × MIC, respectively. Extract of pineapple peel exhibited better antibacterial activity than banana and cassava peels. However, the three waste extracts indicated the antibacterial potential to be developed as natural bactericides to control A. hydrophila bacterial disease.

The activity of Muntingia calabura leaf extract against pathogenic bacteria in fish

Bacterial diseases have emerged as a significant issue within the fish ecosystem, and the use of antibiotics to treat these diseases has detrimental effects on both fish and the environment. Therefore, it is imperative to seek out natural products that are safe for combating fish diseases. This research aims to assess the antibacterial properties of an extract derived from Muntingia calabura against various bacteria, including A. hydrophila, A. salmonicida, E. ictaluri, P. aeruginosa, E. tarda, and V. alginolyticus. M. calabura extract was obtained by soaking with ethanol solvent. This extract has been tested for phytochemical content and characterized by FT-IR. The antibacterial activity of the M. calabura extract was evaluated using the agar diffusion method, employing concentrations of 100, 200, 300, 400, and 500 mg mL-1. The phytochemical analysis of the M. calabura extract revealed the presence of flavonoids, phenolic compounds, saponins, and terpenoids. The results of the FT-IR characterization of M. calabura extract contained O-H, C=O, C=C aliphatic, C=C aromatic and C-O groups. The inhibition tests demonstrated that the M. calabura extract effectively hindered the growth of A. hydrophila bacteria by a range of 8.1 mm to 14.2 mm, A. salmonicida by 9.2 mm to 10.9 mm, E. ictaluri by 8.8 mm to 11.5 mm, P. aeruginosa by 8.1 mm to 12.1 mm, E. tarda by 9.6 mm to 11.4 mm, and V. alginolyticus by 8.2 mm to 12.2 mm. In summary, the extract from M. calabura has the potential to effectively on paper plates and incubated at 30°C for 24 hours.

Isolation and identification of major bacteria from three Ethiopian rift valley lakes live and processed fish, and water samples: implications in sanitary system of fish products

Bacterial pathogens are a great threat to fish production. Gram-negative bacteria are among the major bacterial fish pathogens and are zoonotic with the potential to infect humans. This cross-sectional study was conducted to isolate and identify major gram-negative bacteria from live and processed fish, and water samples from Lakes Hawassa, Langanoo and Ziway. A total of 674 different types of samples: 630 tissue samples (210 samples for each intestine, Kkidney and liver collected from 210 live fish (Oreochromis niloticus, Cyprinus carpio and Clarias gariepinus), 20 processed fish samples from lake Ziway fish processing center and 24 lake water samples were included in the study from each lake. The mean values of pH, temperature, dissolved oxygen and nitrate in all water samples were within the normal range at which most freshwater fish species become non-stressed. Of a total of 674 samples included in the study, bacteria were isolated from 154(22.8%) samples with significant difference (P < 0.05) observed in some isolates with respect to sample origin. Of these 154 isolates, 103(66.8%) isolates were gram-negative bacteria consisting of 15 species based on morphology and a range of biochemical tests. From live fish samples, Escherichia coli was the dominant species with 15 isolates followed by Edwardsiella tarda (12), Salmonella Paratyphi (10), Salmonella Typhi (9), Shigella dysenteriae (7), Shigella flexneri (7), Klebsiella pneumonia (7), Enterobacter aerogenes (6), Enterobacter cloacae (5), Pseudomonas aeruginosa (5), Vibrio parahemolyticus (5), Aeromonas sobria (4), Citrobacter freundii (4), Citrobacter koseri (4) and Plesiomonas shigelloides (3). The detection of the common fecal coliforms (E. coli, K. pneumoniae and E. aerogenes) and Salmonella spp. in processed fish indicates the potential danger of passage of pathogenic bacteria and/or their poisons to humans via infected and/or contaminated fish products. Human infection by pathogenic fish bacteria and food poisoning is possible through contamination of fish product in fish production chain due to inadequate handling, poor hygiene and contact with contaminated water. Therefore, producers, consumers and all other stakeholders need to be cautious during handling, processing and consumption of fish harvested from the study lakes.

Antibacterial Activity of Ethanolic Extracts from Jeringau (Acorus calamus)

Increased resistance of pathogenic bacteria due to the use of antibiotics has become a major concern in the aquaculture industry. Environmentally friendly products are urgently needed to replace antibiotics for the treatments of fish diseases. This study aims to determine the activity of extract of Jeringau (Acorus calamus) as an antibacterial towards Aeromonas hydrophila, Pseudomonas aeruginosa and Vibrio alginolyticus. The A. calamus extract was obtained by maceration using ethanol as a solvent. This extract was tested for its phytochemical content and its antibacterial activity was tested using the agar diffusion method. The treatments used were concentrations of A. calamus extract 200, 300, 400, 500 and 600 mg mL-1. Phytochemical test results of A. calamus extract produced alkaloids, phenolic compounds, saponins, terpenoids and flavonoids. The results of the inhibition test showed that A. calamus extract with a concentration of 200 was able to inhibit the growth of Aeromonas hydrophila bacteria by 13.9 mm, 300 (14.4 mm), 400 (14.8 mm), 500 (16.2 mm), 600 (16.5 mm). On Pseudomonas aeruginosa, the concentrations were 200 (13.9 mm), 300 (14.5 mm), 400 (15.2 mm), 500 (15.5 mm), 600 (16.2 mm). On Vibrio alginolyticus, the concentrations were 200 (15.5 mm), 300 (15.7 mm), 400 (16.4 mm), 500 (18.7 mm), 600 (19 mm). In conclusion, A. calamus extract can be used to inhibit the growth of pathogenic bacteria in fish.

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.

Dietary chitosan promotes the growth, biochemical composition, gut microbiota, hematological parameters and internal organ morphology of juvenile Barbonymus gonionotus.

In this study, we determined the effects of dietary chitosan on the growth, biochemical composition, gut microbiota, and hematological and histological parameters of juvenile Barbonymus gonionotus. Three test diets containing three different concentrations (1, 2, and 3 g kg-1 feed) of dietary chitosan were formulated. A basal diet without dietary chitosan was considered a control, and the fish were reared for 60 days. Comparing the effects of the dietary chitosan-containing diets with those of the control diet, we found that dietary chitosan significantly improved the muscle growth, nutrient and mineral contents, hematological parameters, lactic acid bacterium abundance, and digestive enzyme activities of B. gonionotus. Moreover, dietary chitosan significantly inhibited the growth of pathogenic bacteria in fish. Interestingly, an increase in the dietary chitosan level significantly enhanced the protein contents of the muscles and inversely significantly decreased the lipid contents compared to those with the basal diet. Quantitative study revealed that dietary chitosan significantly enhanced the length of intestinal villi, and qualitative study showed that dietary chitosan considerably reduced the fat content in the liver and improved the morphology of the kidney compared to those with the basal diet. Taken together, our results suggest that the application of dietary chitosan at a dose of 1 g kg-1 feed produced the highest benefit to treated B. gonionotus, indicating its potential for safe use in aquaculture.

Fatty Acids-Enriched Fractions of Hermetia illucens (Black Soldier Fly) Larvae Fat Can Combat MDR Pathogenic Fish Bacteria Aeromonas spp.

Aeromonas spp. cause many diseases in aquaculture habitats. Hermetia illucens (Hi) larvae were used as feed-in aquacultures and in eradicating pathogenic fish bacteria. In the present study, we applied consecutive extractions of the same biomass of BSFL fat using the acidic water–methanol solution. The major constituents of the sequential extracts (SEs) were free fatty acids (FFAs), and fatty acids derivatives as identified by gas chromatography spectrometry (GC-MS). Our improved procedure enabled gradual enrichment in the unsaturated fatty acids (USFAs) content in our SEs. The present study aimed to compare the composition and antimicrobial properties of SEs. Among actual fish pathogens, A. hydrophila and A. salmonicida demonstrated multiple drug resistance (MDR) against different recommended standard antibiotics: A. salmonicida was resistant to six, while A. hydrophila was resistant to four antibiotics from ten used in the present study. For the first time, we demonstrated the high dose-dependent antibacterial activity of each SE against Aeromonas spp., especially MDR A. salmonicida. The bacteriostatic and bactericidal (MIC/MBC) activity of SEs was significantly enhanced through the sequential extractions. The third sequential extract (AWME3) possessed the highest activity against Aeromonas spp.: inhibition zone diameters were in the range (21.47 ± 0.14–20.83 ± 0.22 mm) at a concentration of 40 mg/mL, MIC values ranged between 0.09 and 0.38 mg/mL for A. hydrophila and A. salmonicida, respectively. AWME3 MBC values recorded 0.19 and 0.38 mg/mL, while MIC50 values were 0.065 ± 0.004 and 0.22 ± 0.005 mg/mL against A. hydrophila and A. salmonicida, respectively. Thus, the larvae fat from Hermitia illucens may serve as an excellent reservoir of bioactive molecules with good capacity to eradicate the multidrug-resistant bacteria, having promising potential for practical application in the aquaculture field.

A mini-review: Effect of probiotics on the growth and health of fish

The aquaculture sector industry is growing in order to meet the needs of animal protein at a price that is relatively affordable by various groups of people compared to other animal proteins. The development of the fisheries is influenced by the availability of quality fish free from disease attacks and good growth. Probiotics are good microbes that can suppress the growth of pathogenic microbes and can help accelerate fish growth. Various types of probiotics have been shown to increase the growth of various types of fish. In addition, various types of probiotics can also help prevent attacks of various types of pathogenic bacteria in fish. This article aims to explain various probiotics and the effect of probiotics on the growth and health of fish. Based on the above studies, various probiotics has the potential to be used as an alternative supplement for the Growth and Health of various types of fish.

Impact of mycogenic zinc nanoparticles on performance, behavior, immune response, and microbial load in Oreochromis niloticus.

This work aims to evaluate the antibacterial activity of biological zinc nanoparticles (BIO-ZnONPs) against pathogenic fish bacteria and assess the effect of BIO-ZnONPs on the performance, behavior, and immune response in Nile tilapia (Oreochromis niloticus) as compared to chemical zinc nanoparticles (CH- ZnONPs). Aspergillus niger TS16 fabricated the BIO-ZnONPs were spherical shape with the average size of 45nm and net charge of -27.23mV. Generally, the results indicate that BIO-ZnONPs were more effective than CH- ZnONPs in enhancing the performance properties of Nile tilapia. Five experimental groups of Nile tilapia (initial body weight of 20.2g) were treated with two concentrations of 0.5 and 1mg L-1 from biological and chemical ZnONPs, while the fifth group was served as a control. After ten weeks of treated water with ZnONPs, the performance, feed efficiency parameters, feeding, and swimming behaviors significantly improved in BIO-ZnONPs treated groups (P<0.05). The liver function, LYZ activity, and NBT values were significantly enhanced in the 0.5mg L-1 BIO-ZnONPS group compared to CH- ZnONPs group and control (P<0.05). Furthermore, the lowest cortisol and the highest testosterone and growth hormone levels were recorded in 1mg L-1 BIO-ZnONPs group. Regarding the antibacterial effects, BIO-ZnONPs displayed the lower total bacterial loads in water and fish tissues (intestine, gills, skin, and muscle) and the maximum antibacterial properties against pathogenic bacteria (Listeria monocytogenes, Bacillus cereus, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Aeromonas hydrophila). Our study exemplifies novel findings of BIO-ZnONPs in the promotion of fish health and production and its antibacterial properties in Nile tilapia.

Ozone nanobubble treatment in freshwater effectively reduced pathogenic fish bacteria and is safe for Nile tilapia (Oreochromis niloticus)

High concentrations of certain pathogenic bacteria in water usually results in outbreaks of bacterial diseases in farmed fish. Here, we explore the potential application of an emerging nanobubble technology in freshwater aquaculture, specifically aimed to reduce the concentrations of pathogenic fish bacteria in freshwater, and assess whether nanobubbles are safe for Nile tilapia (Oreochromis niloticus). An ozone nanobubble (NB-O3) treatment protocol was established, based on examination of nanobubble size, concentration, disinfection property, and impact on fish health. A 10-min treatment with NB-O3 in 50 L water generated approximately 2–3 × 107 bubbles/mL, with the majority of bubbles being less than 130 nm in diameter and an ozone level of 834 ± 22 mV oxidation-reduction potential (ORP). A single treatment with water spiked with either Streptococcus agalactiae or Aeromonas veronii effectively reduced the bacterial load by 26–48 fold or 96.11–97.92%. This same protocol was repeated three times. The result was a 22,058 to 109,978 fold reduction in bacteria or 99.93–99.99% decrease. In comparison, bacterial concentrations in the control tanks remained unchanged during the experiments. In Nile tilapia-cultured water with the presence of organic matter (e.g. mucus, feces, bacterial flora, feed, etc.), the disinfection property of NB-O3 was reduced; however, we still observe a reduction of 59.63%, 87.25%, and 99.29% after the first, second, and third consecutive treatments, respectively. To evaluate the safety of NB-O3 on fish, juvenile Nile tilapia were exposed to NB-O3 treatment for 10 min. No mortality was observed during the treatment or 48 h post treatment. Gill histology examination revealed that a single NB-O3 treatment caused no alteration in cell morphology. However, damage in the gill filaments, such as blood congestion, aggregates of basal cells at the secondary lamellae or loss of the secondary lamella was noticed in the fish receiving two or three consecutive exposures within the same day. Results of the experiments conducted in this study suggest that NB-O3 technology is promising for reducing pathogenic bacteria in aquaculture systems and may be useful at reducing the risk of bacterial disease outbreaks in farmed fish.

Chemical composition and antibacterial activity of honey collected from East Nusa Tenggara, Indonesia on pathogenic bacteria in aquaculture

The objectives of this research were to investigate the chemical composition and the antibacterial activity of honey from East Nusa Tenggara, produced by Trigona spp., on pathogenic bacteria in fish. The honey used in this research was collected specifically from Semau and Timor Islands while Aeromonas hydrophila and Vibrio alginoliticus were used as the testing bacteria. The chemical composition tests included moisture content (gravimetric), pH, total sugar (spectrophotometric). The honey was tested for the presence of the following active compounds: alkaloids, flavonoids, tanin, saponins, steroids and terpenoids. Antibacterial activity tests were conducted using “paper disk” method with undiluted honey samples. The moisture content of the Semau honey (33 %) was higher than that of the Timor honey (24.65 %), but the total sugar of the Semau honey ( 6.62 %) was lower than that of the Timor honey (74.22%). All honey from both sources (Semau and Timor) in East Nusa Tenggara contained alkaloids, steroids and terpenoids but did not contain flavonoids, tannins and saponins. Antibacterial tests showed that the honey from both sources, Semau and Timor, showed antibacterial activity against V. Alginoliticus and A. hydrophila; the V. alginolitycus inhibition zone diameters were 8.5 mm and 10.5 mm, respectively, while and the A. hydrophila inhibition zone diameter was 8 mm for both honeys.

Antimicrobial agents derived from heterotrophic bacteria againts pathogenic bacteria

Pathogenic bacteria often cause problems in fish farming. Prevention efforts using synthetic antibiotics may engender negative impacts on the environment. Accordingly, the use of natural antimicrobial compounds is required to minimize the risk. There are several types of heterotrophic bacterias which can produce antimicrobial agents. This study aims to determine the ability of the secondary metabolites extract isolated from heterotrophic bacteria in inhibiting the growth of pathogenic bacteria. The method used in this study was an experimental method. Four isolates of bacterial heterotrophic originating from waters of Sungai Pakning were cultured on nutrient broth for 10 days which would later be extracted by using ethyl acetate. The secondary metabolites extract of the heterotrophic bacteria was tested on 3 pathogenic bacteria that usually attack fish. The antimicrobial test results indicated that the secondary metabolites extract of the heterotrophic bacteria was able to inhibit the growth of Aeromonas salmonicida bacteria from 11.77 to 12.53 mm, Edwarsiella tarda bacteria from 10.70 to 12.40 mm and Edwarsiella ictaluri bacteria from 10.97 to 12.38 mm. Overall, the inhibition of the strongest pathogenic bacteria was JS11 isolates (Bacillus sp. strain SMMA8 code access LN869534.1). Heterotrophic bacteria produced secondary metabolites which can inhibit the growth of pathogenic bacteria in fish. Antimicrobial agents of heterotrophic bacteria are potentially to be developed.