Biological Responses of Nile tilapia Oreochromis niloticus as Influenced by Dietary Florfenicol

Ecotoxicological assessment of microplastics and florfenicol on Acanthopagrus latus: mucus, humoral immune responses and DNA damage

This study evaluated the adverse effects of florfenicol (FLO) (15 mg/kg diet) and microplastics (MPs) (100 and 500 mg/kg diet) on yellowfin seabream, Acanthopagrus latus, over a 10-day exposure period. Fish were exposed to these substances individually and in combination. Tissue, blood, and skin mucus samples were collected on days 1, 4, 7, and 14 post-exposure. Results indicated that both MPs alone and combined with FLO elevated cholesterol, triglyceride, urea, creatinine, and glucose levels. The activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase, alkaline phosphatase (ALP), and creatine kinase were also increased. Conversely, immunological markers such as complement 3, complement 4, immunoglobulin M, lysozyme activity, phagocytic activity, respiratory burst activity, and total protein concentrations decreased. Similar to blood results, the concentrations of alternative complement, total immunoglobulin, lysozyme, and total protein in the mucus were reduced, whereas ALP levels in the mucus increased. These biomarkers did not recover by day 14 in groups exposed to MPs alone or with the antibiotic. FLO concentration in muscle peaked on day 1 and declined by the end of the trial. The FLO alone affected creatinine, cholesterol, total protein, AST, ALT, ALP, and immunological markers, all of which returned to normal by the conclusion of the trial. FLO did not influence the total immunoglobulin in the mucus. MPs, individually and in combination, increased DNA damage in the liver, kidney, spleen, and intestinal tissues. The findings demonstrate that FLO and MPs detrimentally impact fish health, with a more pronounced effect when combined, indicating synergistic toxicity.

Impact of Bambusa vulgaris-supplemented diet on Nile tilapia challenged with Pseudomonas putida: Hematological, immune, and oxidative responses

This study investigated the effects of bamboo shoot extract (Bambusa vulgaris) as a feed additive on the health profiles and infection resistance of Nile tilapia (Oreochromis niloticus) against Pseudomonas putida. Bamboo shoot extract was added at levels of 0 g, 40 g, and 60 g per 1000 g of diet over a 60-day period. The fish were then challenged with a pathogenic P. putida strain. Chemical analysis of the bamboo shoot extract identified 3,5-dinitrophenol and hydroquinone as the two most abundant compounds. Results showed that fish fed bamboo-enriched diets exhibited significantly enhanced levels of red blood cells, hemoglobin, hematocrit, white blood cells, and platelets, and improved erythrocyte cellular and nuclear morphologies, indicating improved health profiles after the challenge. Liver function indicators, including AST, ALT, and ALP, were notably balanced in fish receiving bamboo shoot extract post-challenge (p < 0.05). Blood levels of K+ were lower in the bamboo-fed groups. Additionally, blood levels of Ca++ and Na+ were reduced in fish fed 40 g and 60 g of bamboo, respectively, compared to the control group (p < 0.01). The bamboo extract also enhanced immune and oxidative capacities, as demonstrated by increased catalase, superoxide dismutase, lysozyme activity, and phagocytic activity, along with reduced malondialdehyde levels and elevated serum immunoglobulin M (p < 0.01). Gene expression analysis revealed significant effects of Bambusa vulgaris extract, Pseudomonas infection, and their interaction on the expression of interleukin-1β, interleukin-10, and NK-lysin genes, with varying expression levels at 1, 3, and 7 days post-challenge (p < 0.05). The liver bacterial load in fish exposed to P. putida significantly decreased in the bamboo-fed groups, with the lowest count observed in the 60 g bamboo group. Additionally, survival rates were markedly higher in the bamboo-fed groups compared to the control, with no significant difference between the two bamboo-fed groups. In conclusion, dietary supplementation with bamboo shoot extract enhances hematological parameters, blood cell and nuclear morphology, and increases survival rates in Nile tilapia following infection.

Recovery of intestinal microbial community in Penaeus vannamei after florfenicol perturbation

The concept and application of probiotic intervention for restoring intestinal microbial dysbiosis induced by antibiotics in aquaculture are still in early stages. This study aimed to investigate potential responses of various recovery strategies, including natural recovery and probiotic intervention, in restoring the growth and intestinal microbial community of Penaeus vannamei following florfenicol perturbation. The basal diet (control, CN) was supplemented with florfenicol (FC) or Lactobacillus plantarum W2 (LM) throughout the entire feeding trial. Meanwhile, the basal diet was supplemented with florfenicol for 7 days, followed by a period without florfenicol (natural recovery, FB), or with live strain W2 (probiotic recovery, FM), for a duration of 35 days. Results indicated that dietary supplementation of strain W2, whether continuous or following florfenicol perturbation, along with continuous florfenicol supplementation, significantly enhanced the growth performance of shrimp. Early natural recovery and probiotic intervention did not induce significant alterations in microbial diversity and community structure. Florfenicol perturbation resulted in a decrease in the abundance of potentially beneficial bacteria in intestinal microbial community of shrimp. However, both probiotic intervention and natural recovery strategies gradually reduced the abundance of potentially pathogenic bacteria while increasing the abundance of potentially beneficial ones. The robustness of microbial network decreased during florfenicol perturbation, showed gradual improvement during probiotic recovery, and remained relatively low during natural recovery and continuous florfenicol supplementation. Moreover, the microbial community composition in intestinal habitat significantly differed under various recovery strategies compared to the control. Notably, the microbial community composition of intestinal habitat following probiotic recovery exhibited greater similarity to that of continuous strain W2 supplementation without florfenicol perturbation. In summary, dietary supplementation of florfenicol perturbed intestinal microbial community stability of shrimp, whereas probiotic intervention and natural recovery facilitated the attainment of new stable states by altering keystone taxa. Considering intestinal microbial community stability of shrimp, the recovery of microbial community through probiotic intervention appears to be more effective than natural recovery.

Intestinal Histopathological Aberrations in Oreochromis niloticus Juveniles upon Dietary Florfenicol Administration

The aquaculture use of antibiotics can cause detrimental effects on fish organs and gut microbial dysbiosis. The impact of florfenicol (FFC) on fish intestinal histology, an approved antibiotic, remains unclear. This study aimed to investigate the effects of FFC on Oreochromis niloticus juveniles by administering FFC at 10 mg and 30 mg/kg biomass/day for 30 consecutive days to mimic long-term use. A dose-dependent reduction in feed intake, survival and biomass, with an upsurge in mortalities was observed. Even the therapeutic dose instigated mortalities on day 30 of FFC dosing (FD). Histopathological analysis revealed mild to moderate alterations, including loss of absorptive regions, epithelial degeneration, necrotized areas, intercellular enterocytic space and swollen laminar propria. Post-dosing, the observation of the detachment of lamina propria from the epithelium indicated imminent irritability. Goblet cells reduced drastically on day 30 FD, accompanied by an increase in intraepithelial lymphocytes. However, cessation of dosing for 13 days resulted in the reclamation of goblet cells and absorptive regions, indicating that the intestinal tissues underwent considerable repair after lifting antibiotic pressure. These findings suggested that O. niloticus can tolerate dietary FFC but emphasize the need for responsible use of antibiotics in aquaculture.

Effects of short-term florfenicol exposure on the gene expression pattern, midgut microbiota, and metabolome in the lepidopteran model silkworm (Bombyx mori)

Florfenicol (FF), an alternative veterinary antibiotic for chloramphenicol, has been widely utilized in livestock breeding to prevent and treat bacterial diseases. However, the toxicological effects of FF have yet to be fully disclosed. The domesticated silkworm (Bombyx mori), a lepidopteran model, was selected to assess the toxicological effects of FF dietary exposure with multi-omics. The findings showed that high-dose (250 μg/L) FF exposure increased the whole cocoon weight. High-dose FF exposure affected the species richness and community diversity of the microbiota in the silkworm midgut. Biochemical processes and innate immunity were impacted by FF exposure. The KEGG pathways impacted by the midgut microbiota and their metabolites were compared, and several pathways were found to be related to the two ecosystems. In addition, the innate immunity and lipid metabolism pathways were impacted, and some of the differentially expressed genes were enriched in these pathways. These related pathways may involve crosstalk between the midgut microbiota shift, midgut biological functions, and global gene expression. Therefore, our study also advances the application of the silkworm larval model in assessing antibiotic metabolic toxicity and provides novel insights into the potential risks of FF.

Impacts of florfenicol on immunity, antioxidant activity, and histopathology of Oreochromis niloticus: a potential protective effect of dietary spirulina platensis

The misuse of antibiotics enhances the development of resistant microorganisms and decreases the efficacy of treatments. Florfenicol (FF) is one of the antibiotics approved for use in aquaculture in Egypt. Because of its extensive usage, potential negative impacts on aquatic creatures are a major concern. This motivates us to search for an appropriate neoadjuvant to work synergistically with FF and reduce adverse effects. Results from this study will contribute towards improving the understanding of the impacts of FF on Oreochromis niloticus and the possible amelioratory effects of Spirulina platensis algae (SP). O. niloticus (n = 240; 40 ± 2.5 g) were fed on two diets supplemented with or without SP for 4 weeks, then divided into four treatments each in three replicates (n = 60/treatment). G1; was fed a control diet, and the other groups were fed diets supplemented with FF (10 mg /kg of BW, G2), SP (2 g/kg of diet, G3), or FF + SP (G4) for 10 days. Among the four groups, the SP group (G3) had the best immunostimulatory effects as observed by a significant (p < 0.05) elevation in phagocytic activity, phagocytic index, IL6, and TNF-α. The treatment with FF had significantly impacted hepatic and renal tissues, as the values of liver enzymes and creatinine demonstrated tissue deterioration and also resulted in oxidative stress, which was expressed by an increase of GPx, CAT, and SOD in (G2). Additionally, the combined FF + SP improved the hematological parameters and decreased the oxidative damage induced by FF (G4). Thus, it was clear that FF has harmful effects on O. niloticus and that SP can modulate such impacts. These data recommend the use of SP as an effective immunostimulant and a probable adjuvant to FF in O. niloticus diets to attain maximum disease resistance.

Effects of Resource Availability and Antibiotic Residues on Intestinal Antibiotic Resistance in Bellamya aeruginosa

Widespread and inappropriate use of antibiotics has been shown to increase the spread of antibiotics and antimicrobial resistance genes (ARGs) in aquatic environments and organisms. Antibiotic use for the treatment of human and animal diseases is increasing continuously globally. However, the effects of legal antibiotic concentrations on benthic consumers in freshwater environments remain unclear. In the present study, we tested the growth response of Bellamya aeruginosa to florfenicol (FF) for 84 days under high and low concentrations of sediment organic matter (carbon [C] and nitrogen [N]). We characterized FF and sediment organic matter impact on the bacterial community, ARGs, and metabolic pathways in the intestine using metagenomic sequencing and analysis. The high concentrations of organic matter in the sediment impacted the growth, intestinal bacterial community, intestinal ARGs, and microbiome metabolic pathways of B. aeruginosa. B. aeruginosa growth increased significantly following exposure to high organic matter content sediment. Proteobacteria, at the phylum level, and Aeromonas at the genus level, were enriched in the intestines. In particular, fragments of four opportunistic pathogens enriched in the intestine of high organic matter content sediment groups, Aeromonas hydrophila, Aeromonas caviae, Aeromonas veronii, and Aeromonas salmonicida, carried 14 ARGs. The metabolic pathways of the B. aeruginosa intestine microbiome were activated and showed a significant positive correlation with sediment organic matter concentrations. In addition, genetic information processing and metabolic functions may be inhibited by the combined exposure to sediment C, N, and FF. The findings of the present study suggest that antibiotic resistance dissemination from benthic animals to the upper trophic levels in freshwater lakes should be studied further.

Impacts of Oral Florfenicol Medication and Residues on the Kidney and Liver of Nile Tilapia Oreochromis niloticus (L.)

Florfenicol (FFC), an approved aquaculture antibiotic, is administered in feed at doses of 10-15 mg kg biomass^-1 day^-1 for 10 successive days. In this study, healthy Oreochromis niloticus were fed with 0-10 times the therapeutic dose of 15 mg kg biomass^-1 day^-1 for 10 days and tracked for 43 days post dosing. Assessments of residue accrual and depletion, oxidative stress, serum biochemistry, histopathology and extent of kidney and liver damages were made. FFC dosing reduced the feed intake significantly. The therapeutic dose produced no mortalities on day 10. Dose-dependent alterations in serum biochemistry were noted upon dosing. Several histopathological alterations were observed in the kidney and liver, which vindicated the toxic potentials of FFC. The residual FFC and florfenicol amine (FFA) accrual, depletion and oxidative stress responses, such as increased malondialdehyde, total nitric oxide, ferric reducing antioxidant power and reduced glutathione S-transferase activity, were documented. The dietary FFC persuaded the physiological state of O. niloticus, the effects of which normalized sparsely with time upon cessation of dosing at the higher doses. The study provided a brief outlook on the physiological responses upon oral FFC administration, which should be kept in mind during its application for fish health safety purposes.