A new potential therapeutic remedy against Aeromonas hydrophila infection in rainbow trout (Oncorhynchus mykiss) using tetra, Cotinus coggygria

Pharmacokinetic behaviour and pharmacokinetic-pharmacodynamic integration of doxycycline in rainbow trout (Oncorhynchus mykiss) after intravascular, intramuscular and oral administrations

OBJECTIVE

Doxycycline (DO) has been used in fish for a long time, but there are some factors that have not yet been clarified regarding its pharmacokinetic (PK) and pharmacodynamic (PD) properties. Therefore, the aim of this study was to investigate the PK and PK/PD targets of DO after 20 mg/kg intravascular (IV), intramuscular (IM) and oral (OR) gavage administration in rainbow trout (Oncorhynchus mykiss).

METHODS

Plasma samples were collected at specific time points and subsequently analysed by HPLC-ultraviolet. The PK/PD indices were calculated based on the MIC90 (Aeromonas hydrophila and Aeromonas sobria) values obtained for the respective bacteria and the PK parameters obtained for DO following both IM and OR administration.

RESULTS

After IV administration, the elimination half-life (t1/2 ʎz), area under the concentration vs. time curve (AUC), apparent volume of distribution at steady-state and total body clearance of DO were 34.81 h, 723.82 h µg/mL, 1.24 L/kg and 0.03 L/kg/h, respectively. The t1/2λz of the DO was found to be 37.39 and 39.78 h after IM, and OR administration, respectively. The bioavailability was calculated 57.02% and 32.29%, respectively, after IM and OR administration. The MIC90 of DO against A. hydrophila and A. sobria was 4 µg/mL. The PK/PD integration showed that DO (20 mg/kg dose) for A. hydrophila and A. sobria with MIC90 ≤4 µg/mL achieved target AUC/MIC value after IM administration.

CONCLUSIONS

These results suggest that when rainbow trout was treated with 20 mg/kg IV and IM administered DO, therapeutically effective concentrations were reached in the control of infections caused by A. hydrophila and A. sobria.

Antibacterial Mechanisms and Antivirulence Activities of Oridonin against Pathogenic Aeromonas hydrophila AS 1.1801

Aeromonas hydrophila, a Gram-negative bacterium widely found in freshwater environments, acts as a common conditional pathogen affecting humans, livestock, and aquatic animals. In this study, the impact of oridonin, an ent-kaurane diterpenoid compound derived from Rabdosia rubescens, on the virulence factors of A. hydrophila AS 1.1801 and its antibacterial mechanism was elucidated. The minimum inhibitory concentration (MIC) of oridonin against A. hydrophila AS 1.1801 was 100 μg/mL. Oridonin at inhibitory concentrations could significantly increase the electrical conductivity in the supernatant and escalate nucleic acid leakage (p < 0.01). This effect was concomitant with observed distortions in bacterial cells, the formation of cytoplasmic cavities, cellular damage, and pronounced inhibition of protein and nucleic acid synthesis. Additionally, oridonin at inhibitory levels exhibited a noteworthy suppressive impact on A. hydrophila AS 1.1801 across biofilm formation, motility, hemolytic activity, lipase activity, and protease activity (p < 0.05), demonstrating a dose-dependent enhancement. qRT-PCR analysis showed that the gene expression of luxR, qseB and omp were significantly downregulated after oridonin treatment in A. hydrophila AS 1.1801 (p < 0.05). Our results indicated that oridonin possessed significant antibacterial and anti-virulence effects on A. hydrophila AS 1.1801.

An update about beneficial effects of medicinal plants in aquaculture: A review

Aquaculture is an essential and growing component of agricultural and global ecosystems worldwide. Aquaculture provides more than 25% of the total aquatic food consumption by humans. The development of the aquaculture industry should be followed in successive industrial years, and therefore it is necessary to pay attention to the management and type of farming system that is compatible with the environment. The use of antibiotics for disease control has been criticised for their negative effects, including the emergence of antibiotic-resistant bacteria, the suppression of the immune system and the environment, and the accumulation of residue in aquatic tissues. The use of these products reduces the need for treatments, enhances the effect of vaccines, and, in turn, improves production indicators. Medicinal plants have increasingly been used in recent years as a disease control strategy in aquaculture, boosting the immune system of aquatic animals and helping to develop strong resistance to a wide range of pathogens. Therefore, this review aims to provide an overview of the recent evidence on the beneficial use of medicinal plants to promote growth and strengthen the immune system in farmed aquatic animals.

Effect of dietary celery (Apium graveolens) on the growth performance, immune responses, and bacterial resistance against Vibrio anguillarum of European seabass (Dicentrarchus labrax)

In this study, we evaluated to reveal the effects of aqueous methanolic extract of celery (Apium graveolens) on the growth performance, immune responses, and resistance against Vibrio anguillarum in European seabass (Dicentrarchus labrax). For this purpose, twenty fish (initial mean weight of 4.80 ± 0.06 g) were placed into twelve tanks (400 L) in triplicate and fish were fed with control (C) and three different levels (0.01, 0.05, and 0.1 g/kg) of A. graveolens (AG) extract-containing diets (AG0.01, AG0.05, and AG0.1) for 30 days. Blood and tissue (kidney, spleen, and intestine) samples were taken from the fish every 10 days during the study to determine the immune responses of the fish. Respiratory burst activity (RBA) was significantly decreased in the AG0.1 group compared to all other groups on the 10th day of the study (P < 0.05). Significance was noticed in the RBA of fish in all AG groups compared to the C group (P < 0.05) on the 30th day of the experiment Lysozyme activity (LYS) was raised on the 10th day of the study in all celery groups compared to the C group (P < 0.05). No differences in the myeloperoxidase activity (MPO) were observed among the experimental groups (P > 0.05). The final mean weight (FMW) was not affected in any experimental groups (P > 0.05). However, in the AG0.05 group, the specific growth rate (SGR) increased, and the feed conversion ratio (FCR) decreased compared to other groups (P < 0.05). IL-1β in the kidney was highly elevated in the AG0.01 group on the 20th day of the study (P < 0.05). Similar results were observed on IL-6, IL-8, and TNF-α expression in the kidney (P < 0.05). Anti-inflammatory responses (IL-10 and TGF-β) also increased in all experimental groups and tissues compared to the C group (P < 0.05). COX-2 was upregulated on the 20th day of the study in all tissues (P < 0.05). At the end of the feeding trial, the survival rate of the AG0.1 group in fish infected with Vibrio anguillarum infection was higher than the C group. Dietary celery extract did not affect growth performance directly but increased innate immune responses and a high survival rate. Overall, compared to the control group, the growth, immunity, and resistance of European seabass fed with a diet containing 0.05 g/kg celery aqueous methanolic extract has been improved, and this could be used as an immunostimulant feed additive.

Effects of dietary marine sulphated polysaccharides (Algimun®) on growth performance, immune responses and disease resistance of juvenile gilthead seabream (Sparus aurata) to Photobacterium damselae subsp. piscicida

The present study evaluated the effects of a dietary mix of marine sulphated polysaccharides, named Algimun® (AL), supplementation to gilthead seabream (Sparus aurata) juveniles in terms of growth performance, immune responses, and resistance against Photobacterium damselae subsp. piscicida. A total of 240 fish (initial mean weight of 6.00 ± 0.03 g) was randomly separated into 12 tanks (400 L, 20 fish per tank) distributed in four replicates. Fish were fed three experimental diets: a basal diet (Control), and a basal diet with two inclusion rates of Algimun® as 3 g/kg (AL0.3) and 5 g/kg (AL0.5) for 30 days before bacterial infection with P. damselae subsp. piscicida. After a 30-day feeding-period, growth performance was significantly improved in AL0.3 and AL0.5 groups compared to the control group (P < 0.05). AL0.3 and AL0.5 groups showed significantly higher lysozyme activity and myeloperoxidase activity when compared to the control group (P < 0.05). The gene expression of immune mediators (IL-1β, IL-6, IL-10, IL-18, TNF-α and COX-2) was significantly upregulated in the intestine, spleen and head kidney in AL0.3 and AL0.5 groups when compared to the control group (P < 0.05). Eight days post-challenge, the survival rate against P. damselae subsp. piscicida was numerically higher in fish within AL0.3 and AL0.5 groups compared to control (+20%). The study findings suggest that marine sulphated polysaccharides (Algimun®) could be used as an immunomodulator in gilthead seabream to support animal's health and boost resistance in case of disease outbreak.

Fermented medicinal herbs improve hematological and physiological profile of Striped catfish (Pangasianodon hypophthalmus)

This study sought to determine the effect of fermented medicinal herbs (FMH), i.e. cutchery ( Kaempferia galanga), turmeric ( Curcuma longa) and curcuma ( Curcuma xanthorrhiza) in combination with molasses and probiotic drink (Yakult), administered orally on the hematological and physiological profile of striped catfish ( Pangasianodon hypophthalmus). A complete randomized design (CRD) experiment was used with four levels of treatments, namely P0 (control), P1 (FMH 100 mL/kg), P2 (FMH 200 mL/kg) and P3 (FMH 300 mL/kg) of feed. The fish were kept in a farm in cages at 75 fish/m ³ and fed with the experimental diets for 60 days. The results revealed that FMH (P2) dietary administration improved hematological and physiological profile of catfish, i.e total erythrocytes of 2.81 x 10 ⁶ cells/mm ³, hematocrit values of 39.00%, hemoglobin levels of 10.73 g/dL, total leukocytes of 11.41 x 10 ⁴ cells/mm ³, blood glucose 97.33 mg/dL, and total serum protein 4.10 mg/dL compared to controls with 1.89 x 10 ⁶ cells/mm ³, 32.33 %, g/dL, 9.67 x 10 ⁴ cells/mm ³, 67.33 mg/dL, and total serum protein of 3.10 mg/dL, respectively. Moreover, the diet improved special growth rate, feed conversion ratio, feed efficiency and the survival rate of catfish. The hematological and physiological profile of catfish improvement are considered to be due to the content of secondary metabolites of FMH, namely curcuminoids, vitamin C, essential oils, tannins, and flavonoids, which trigger immunostimulation. The presence of curcuminoids provide an antioxidant effect on cell membranes reducing erythrocyte cell membrane damage due to oxidation. Similarly, flavonoids are natural antioxidants, which are credited with the ability of reducing free radicals and anti-free radicals.

Antibacterial Potential of Caesalpinia coriaria (Jacq) Willd Fruit against Aeromonas spp. of Aquaculture Importance

Simple Summary

Aquaculture remains an important source of food, however, aquaculture systems are affected by different factors including the appearance of resistant or multiresistant bacteria to antimicrobials. An alternative in the search for new treatments for these bacteria is plant extracts. The aim of the present study was to determine the antibacterial activity of Caesalpinia coriaria fruit hydroalcoholic extract and gallic acid over Aeromonas hydrophila, Aeromonas veronii, and Aeromonas dhakensis to identify new molecules for the treatment of diseases caused by Aeromona spp. The hydroalcoholic extract of Caesalpinia coriaria and its fractions have antibacterial activity against Aeromonas hydrophila, Aeromonas veronii, and Aeromonas dhakensis and could be alternatives for the treatment of diseases caused by the genus Aeromonas.

Abstract

Aquaculture is an important source of food and livelihood for hundreds of millions of people around the world, however, aquaculture systems are affected by different factors, among them the appearance of resistant or multiresistant bacteria to antimicrobials. The secondary metabolites of plants have been proposed as alternatives for the treatment of these bacteria. The aim of the present study was to determine the antibacterial activity of Caesalpinia coriaria fruit hydroalcoholic extract and gallic acid over Aeromonas hydrophila, Aeromonas veronii,  and Aeromonas dhakensis to identify new molecules for the treatment of diseases caused by Aeromonas spp. The C. coriaria fruit hydroalcoholic extract (HECc) was obtained by hydroalcoholic maceration and subjected to bipartition with ethyl acetate and water to obtain an aqueous fraction (Ac-FrCc) and an organic fraction (Ac-FrEtCc); gallic acid was purchased commercially. The Minimum Inhibitory Concentration (MIC), Minimum Bactericidal Concentration (MBC), MBC/MIC ratio, and cytotoxicity of HECc, its fractions, and gallic acid were determined. The results indicate that HECc fractions (Ac-FrCc and Ac-FrEtCc) and gallic acid have bactericidal activity against A. hydrophila and A. dhakensis, but only gallic acid showed bactericidal activity against A. veronii. The HECc and Ac-FrCc showed no toxicity, Ac-FrEtCc showed low toxicity, and gallic acid showed medium toxicity. The HECc, Ac-FrCc, and Ac-FrEtCc may be alternatives for the treatment of diseases caused by the genus Aeromonas, however, in vivo assays are necessary to corroborate these results.

Preparation and characterization of glucose-conjugated super-paramagnetic iron oxide nanoparticles (G-SPIONs) for removal of Edwardsiella tarda and Aeromonas hydrophila from water

The present research was conducted to prepare efficient G-SPIONs by co-precipitation to remove Edwardsiella tarda and Aeromonas hydrophila from the aqueous solution. The synthesized G-SPIONs were characterized by UV-Vis spectrophotometer, DLS, FEG-TEM, FT-IR, XRD, and VSM analysis. The results showed that the synthesized G-SPIONs had super-paramagnetic properties (58.31 emu/g) and spherical shape (16 ± 3 nm). The antibacterial activity was assessed in sterilized distilled water at different G-SPIONs concentrations viz. 0, 1.5, 3, 6, 12, 24, 48, 120, and 240 mg/L against E. tarda and A. hydrophila with various bacterial loads viz. 1 × 10³ , 1 × 10⁴ , 1 × 10⁵ , 1 × 10⁶ , and 1 × 10⁷  CFU/ml at different time intervals 15, 30, 45, and 60 min. At a lower bacterial load of E. tarda and A. hydrophila 1 × 10³ -1 × 10⁴  CFU/ml, 100% bacterial load was removed by 15 min exposure with NPs concentration 6-48 mg/L and 1.5-6 mg/L, respectively. Cent percent bacterial removal was observed in both the bacterial species even at higher bacterial load (1 × 10⁵ -1 × 10⁷  CFU/ml) by increasing exposure time (15-60 min) and nanoparticle concentration as well (24-240 mg/L). At an initial bacterial load of E. tarda and A. hydrophila (1 × 10³ -1 × 10⁷  CFU/ml), the EC₅₀ ranged between 0.01-6.51 mg/L and 0.02-3.84 mg/L, respectively, after 15-60 min exposure. Thus, it is concluded that the antibacterial effect of G-SPIONs depends on concentration and exposure time. Hence, G-SPIONs can be used as an antibacterial/biocidal agent to treat Edwardsiellosis and Aeromonosis disease in aquaculture.

Oral administration of Sargassum polycystum extracts stimulates immune response and increases survival against Aeromonas hydrophila infection in Oncorhynchus mykiss

This study investigated the immunomodulatory effects of Sargassum polycystum extract administration in rainbow trout (Oncorhynchus mykiss). S. polycystum methanolic extract was administered orally using feeding needles to individual rainbow trout at the dose of 0 (control), 1 (S1), 3 (S3) and 5 (S5) mg/100 μl/per fish twice a day for 7 days. On 1st, 5th, 3rd and 7th day, blood and tissues were collected from the fish and changes in humoral immune responses and immune-related gene expressions were determined. The result of oxidative radical production showed no difference during early stage of the experiment and was lately decreased (P < 0.05). Lysozyme activity increased on 3rd and 7th day of the study in S5 fish group and on 5th day in S3 group compared to control (P < 0.05). Myeloperoxidase activity had an increased level on the 1st and 3rd day in S1, S5 and S5 fish groups, respectively. IL-1β gene was significantly up-regulated in kidney and intestine in all experimental groups (except on the 1st day, in the intestine of S5 fish group) compared to control (P < 0.05). IL-8 gene expression was elevated on 1st and 3rd day in kidney of all experimental fish groups. IL-6 transcript enhanced in a dose-dependent manner on 3rd and 7th day. IL-10 and IL-12 genes were also up-regulated. Survival in all treated fish groups challenged with Aeromonas hydrophila was significantly increased compared to that of control. The highest survival rate was recorded in S5 fish group (83.65%) followed by S3 fish group (82.62%). Our results suggest that S. polycystum aqueous methanolic extract is an effective immunostimulant and provide protection against A. hydrophila infection in rainbow trout at a dose of 3-10 mg/20 g body weight/day.

Modulatory effects of laurel-leaf cistus (Cistus laurifolius) ethanolic extract on innate immune responses and disease resistance in common carp (Cyprinus carpio)

Medicinal herbs are used for growth promotion, disease control and other health benefits in aquaculture industry. Here, we examined the effect of dietary laurel-leaf cistus (Cistus laurifolius) ethanolic extract on growth performance, digestive enzyme activity, haematological profile and nonspecific immune responses in common carp (Cyprinus carpio). In addition, resistance against Aeromonas hydrophila infection was examined. Common carp was fed diets containing 0 (Control), 0.1 (CL0.1), 0.5 (CL0.5) and 1 (CL1) g kg^-1 laurel-leaf cistus extract for 45 days. After 30 days, superoxide anion production (SAP) increased in CL0.1 and CL0.5 fish groups and at the end of the study all experimental fish groups had higher SAP compared to that of the control (P ˂ 0.05). Lysozyme activity (LA) was elevated in CL0.5 and CL1 treated groups on 30th day (P < 0.05), and this increase was only observed in C0.1 fish group at the end of study compared to control (P ˂ 0.05). Myeloperoxidase activity was significantly increased in CL0.5 and CL1 fish groups at the end of study. IL-1βgene expression was significantly increased in treated fish in a dose-depended manner. Similar results were observed for transcription of IL-6 and IL-8 (P < 0.05). Anti-inflammatory cytokines, IL-10 and TGF-β were highly up-regulated in the intestine and head kidney of CL treated fish groups compared to control (P < 0.05). At the end of experiment, significantly higher final body weight, weight gain, and specific growth rate were obtained in CL0.1 treated fish group compared to control. However, growth was negatively affected in CL1 fish group (P < 0.05). CL1 fish group had also a significantly higher FCR. Amylase activity was significantly increased in all experimental fish groups compared to control (P ˂ 0.05). Trypsin activity was decreased in CL0.1 and CL1 fish groups (P ˂ 0.05). WBC and RBC were significantly increased (P ˂ 0.05) in CL0.5 and CL1 fish groups, whereas haemoglobin, haematocrit, mean cell, mean cell haemoglobin contents were no significantly changed among control and treatment groups. Result of challenge test with A. hydrophila exhibited that survival rate in all treatment groups was significantly higher than that of control. These findings demonstrated that laurel-leaf cistus at 0.1 g kg^-1 can be a suitable candidate for growth promotion, immune system induction and infection control in fish.

Antioxidant enzyme activities and immune responses in rainbow trout (Onchorhynchus mykiss) juveniles fed diets supplemented with dandelion (Taraxacum officinalis) and lichen (Usnea barbata) extracts

In the present study, antioxidant activity, immune responses, and growth performance of rainbow trout (Onchorhynchus mykiss) juveniles fed with diets supplemented with dandelion (Taraxacum officinalis) and lichen (Usnea barbata) extracts were assessed. Four different concentrations of aqueous methanolic extract of the plants (0% (control), 0.1%, 0.5%, and 1% (D, dandelion; L, lichen) were added to the diets, and fish were fed for 75 days. On the 15^th, 45^th, and 75^th day of the study, liver antioxidant enzyme activities were determined, and immune responses were determined every 15^th day. The results showed that SOD activity increased in the fish group of 0.1% D on the 15^th and 45^th day compared to control; however, it was lower in all the lichen extract-treated groups than in control at almost all sampling times, except on the 15^th day in the 0.1% L group. CAT activity showed an increased value (P < 0.05) in 0.5% L and 1% L treated fish groups on the 15^th day, in fish of 1% D and 1% L groups on 45^th and on 75^th day in 0.1% D group. GPX activity increased on the 15^th day of the study in fish of 0.1% D group, on the 45^th day in 1% D and 1% L groups and on the 75^th day in fish of 0.5% D, 0.1% D, and 0.5% L groups (P < 0.05). G6PDH enhanced in all treatment groups compared to control on the 15^th day, except in 0.1% L and 0.5% L groups. An elevated G6PDH activity was also observed on the 75^th day of the study in 0.5% D, 1% D, and 0.5% L fish groups. An increase on lipid peroxidation (LP) was observed in all L groups on the 45^th day of the study. Lysozyme activity was determined to be the highest in 0.5% and 1% L on the 45^th day, in 0.1% L on the 60^th day and in the 0.5% L fish group on the 75^th day compared to control (P < 0.05). Myeloperoxidase was found to be the highest at the end of the study in 1% L fish group compared to the control (P < 0.05). In conclusion, we suggest the use of dandelion to combat oxidative stress and to lower FCR and the use of lichen to modulate the immune response in rainbow trout. The use of such products will be economical for aquaculture and harmless for the environment.

Effects of Greek juniper (Juniperus excelsa) extract on immune responses and disease resistance against Yersinia ruckeri in rainbow trout (Oncorhynchus mykiss)

This study investigated the effects of Greek juniper extract on immune responses of rainbow trout. In this experiment, 4 doses [0 (Control), 1 (J1), 4 (J4) and 8 (J8) mg/kg] of the extract were administered orally using an oral gavage twice a day for 14 days. Immune responses were measured on 7th and 14th days. On 14th day, Yersinia ruckeri was injected intraperitoneally to all fish of all groups. On 14th day, ORP in fish of J1 group increased significantly. Lysozyme activity (LA) was increased in J8 group on 7th day (p < .05). On 14th day, a significant decrease was determined in J1 and J4 treatments in LA. Myeloperoxidase activity was significantly decreased in all groups irrespective of sampling times (p < .05). Interleukin (IL)-1β was significantly elevated in fish of J8 group on 7th day. IL-8 increased in fish of J8 and J4 groups on 7th day of the study. IL-12 gene expression was significantly up-regulated in J8 fish group on 7th day, and in J4 fish group on 14th day. Survival rate was higher in J8 treatment compared to the control and other treatments (p < .05). The results suggest that Juniperus excelsa provides protection against Y. ruckeri in rainbow trout.

A novel herbal immunostimulant for rainbow trout (Oncorhynchus mykiss) against Yersinia ruckeri

In this 21-day study, we examined the effects of the aqueous methanolic extract of thin-skinned plum (Prunus domestica) on growth, immune response and resistance to a pathogenic bacterium, Yersinia ruckeri in rainbow trout (Oncorhynchus mykiss). Fish were fed with diets containing thin-skinned plum extract doses as 0 (Control) 0.1 (PD01), 0.5 (PD05) and 1% (PD1) ad libitum twice in a day. At the end of the study, growth was affected positively but not significantly. Feed conversion ratio (FCR) was decreased in the PD01 group (P < 0.05). There were elevated respiratory burst and potential bacterial killing activities on the 7th day in the PD1 fish group. No differences were observed in lysozyme activity (P > 0.05). An increased myeloperoxidase activity was recorded on the 14th day of study. Expression of interleukin and COX-2 genes was elevated on the 7th day of study in the kidney and intestine of treated fish. Histological results indicated no marked changes in organs (gill, kidney, liver and spleen) of PD treated fish groups. Challenge results of fish in all plum extract-treated groups showed an increased survival rate against Y. ruckeri (P < 0.05). This study indicated that the thin-skinned plum aqueous methanolic extract could improve innate immunity, survival against Y. ruckeri and decrease the FCR level.