Chronic toxicity of sediment-bound triclosan on freshwater walking catfish Clarias magur: Organ level accumulation and selected enzyme biomarker responses.

Triclosan (TCS) is a biocide widely used in personal care and medicinal products. TCS persists in sediments and has been detected worldwide, making sediments a vital route of TCS exposure to aquatic organisms. This experiment explored the bioaccumulation and toxicological effects of TCS-contaminated sediment. The study revealed that the half-life of TCS in the sediment-water system was 21.52 days. Exposure of Clarias magur juveniles to 0.4 and 0.8 mg kg-1 TCS-spiked sediment resulted in high Biota-Sediment Accumulation Factor (BSAF) with the highest bioaccumulation in the liver (29.62-73.61 mg kg-1), followed by gill (9.22-17.57 mg kg-1), kidney (5.04-9.76 mg kg-1), muscle (2.63-4.87 mg kg-1) and brain (1.53-3.20 mg kg-1). Furthermore, a concentration-dependent increase in oxidative stress biomarkers such as superoxide dismutase (SOD), catalase (CAT) and glutathione-S-transferase (GST) was documented during 45 days of exposure in gill, liver, kidney, muscle, and brain tissues of exposed fish. A similar increasing trend was also recorded for liver transaminase enzymes such as glutamic oxaloacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT) during the experimental period compared to control. Serum biochemical analysis revealed a significant time and concentration-dependent increase in serum glucose, serum GOT, and serum GPT, while serum total protein and albumin decreased significantly during exposure. These findings demonstrate high bioaccumulative and toxic nature of TCS in fish, promoting multiple physiological and biochemical dysfunctions through sediment exposure. The study underscores the urgent need for strengthened regulations and robust monitoring of triclosan across various environmental matrices, including sediment, to mitigate the detrimental impacts of TCS effectively.

Chitosan Gel Prepared with Citric Acid as the Food Acidulant: Effect of the Chitosan Concentration and Gel pH on Physicochemical and Functional Properties of Fish Protein Emulsion Sausages.

Citric acid is a popular food acidulant with versatile utility as a preservative and acidity regulator in the meat industry, owing to its unique three pK a values, which can be combined with the natural biopolymer chitosan to improve food quality. The scientific incorporation of a minimal range of chitosan and pH through organic acid additions for chitosan solubilization in the fish sausages can effectively improve their quality through their synergistic effect. Optimum conditions for emulsion stability, gel strength, and water holding capacity were found to be at a low concentration of chitosan, that is, 0.15 g at pH of 5.0, with their corresponding values of 42.55 ± 0.43 N mm, 94.91 ± 0.24, and 90.67 ± 0.50%. Lower pH ranges increased hardness and springiness values, and higher pH levels increased cohesiveness values at varying ranges of chitosan. Sensory analysis revealed tangy and sour flavors in the samples with lower pH.

Histopathological changes and tissue residue concentrations of monosex Nile tilapia (Oreochromis niloticus, L) fries exposed to oxytetracycline.

The current study evaluated the biosafety of oxytetracycline (OTC) exposure for 30 days in monosex Oreochromis niloticus fries. The fries were exposed to OTC for 3 h/day for 30 days at 350 (0.5X), 700 (1X), 2100 (3X), 3500 (5X), and 7000 (10X) mg/L and compared with control (0X). The OTC exposure at 5X and 10X concentrations caused 100% mortality within 4 days and 5 min, respectively. The mortalities recorded in 0.5X, 1X, and 3X groups were 3.33 ± 1.15%, 14.67 ± 1.15%, and 47.33 ± 11.37% on day 30, respectively. The feed intake was decreased up to 23.33% in the 3X group during the exposure period. The OTC residue levels on 30-day exposure were 216.53 ± 14.71, 450.56 ± 44.31, and 1141.26 ± 63.64 µg/kg, which reduced to 40.40 ± 3.25, 76.68 ± 2.77, and 95.61 ± 5.13 µg/kg after 15 days of termination of exposure in the 0.5X, 1X, and 3X groups, respectively. The histopathological changes observed in the 1X group were epithelial detachment, desquamation of secondary lamellar epithelium, lamellar fusion, and inflamed cartilaginous core in the gills, alteration in the integrity of gut mucosa, degeneration of muscularis mucosae and necrosis in the intestine, the disintegration of the nephritic tubule, necrosis, and glomerulopathy in the kidney, and dilated vascular duct, necrotized hepatic tissue, diffused hepatic parenchyma, vacuolation, and fatty changes in the liver. The OTC exposure induced marked tissue changes histologically in a dose- and time-dependent manner, which undoubtedly reduced the growth of tilapia. Supplementary Information: The online version contains supplementary material available at 10.1007/s10499-022-00892-w.

Biomarkers-based assessment of triclosan toxicity in aquatic environment: A mechanistic review.

Triclosan (TCS), an emergent pollutant, is raising a global concern due to its toxic effects on organisms and aquatic ecosystems. The non-availability of proven treatment technologies for TCS remediation is the central issue stressing thorough research on understanding the underlying mechanisms of toxicity and assessing vital biomarkers in the aquatic organism for practical monitoring purposes. Given the unprecedented circumstances during COVID 19 pandemic, a several-fold higher discharge of TCS in the aquatic ecosystems cannot be considered a remote possibility. Therefore, identifying potential biomarkers for assessing chronic effects of TCS are prerequisites for addressing the issues related to its ecological impact and its monitoring in the future. It is the first holistic review on highlighting the biomarkers of TCS toxicity based on a comprehensive review of available literature about the biomarkers related to cytotoxicity, genotoxicity, hematological, alterations of gene expression, and metabolic profiling. This review establishes that biomarkers at the subcellular level such as oxidative stress, lipid peroxidation, neurotoxicity, and metabolic enzymes can be used to evaluate the cytotoxic effect of TCS in future investigations. Micronuclei frequency and % DNA damage proved to be reliable biomarkers for genotoxic effects of TCS in fishes and other aquatic organisms. Alteration of gene expression and metabolic profiling in different organs provides a better insight into mechanisms underlying the biocide's toxicity. In the concluding part of the review, the present status of knowledge about mechanisms of antimicrobial resistance of TCS and its relevance in understanding the toxicity is also discussed referring to the relevant reports on microorganisms.

Dose-dependent co-infection of Argulus sp. and Aeromonas hydrophila in goldfish (Carassius auratus) modulates innate immune response and antioxidative stress enzymes.

Co-infection with parasites and bacteria is of frequent occurrence in aquaculture, leads to growth impedance otherwise mortality in fish depending on the varying degree of a load of primary pathogen either parasite or bacteria. The mechanistic regulation of immune response during co-infection in fish has merely documented. The aim of this study was to determine the impact of co-infection with Aeromonas hydrophila at three exposure doses of Argulus sp. on the innate immune responses and antioxidative stress enzymes of goldfish (Carassius auratus). The experimental fish were randomly distributed into eight treatment groups viz. T1 (control group without Argulus and A. hydrophila infection), T2 (fish exposed to a sub-lethal dose of A. hydrophila), T3 (low Argulus-infested fish), T4 (T3 + sub-lethal dose of A. hydrophila), T5 (moderate Argulus-infested fish), T6 (T5 + sub-lethal dose of A. hydrophila), T7 (high Argulus-infested fish) and T8 (T7+ sub-lethal dose of A. hydrophila) in duplicates. After distributing experimental fish into their respective treatment group, A. hydrophila was injected to T2, T4, T6 and T8. After the bacterial challenge, four fish from each experimental group were randomly sampled on 24, 72, and 168 h and subjected to the hematological, innate immune parameters and enzymatic analysis. In the co-infection group T8, a high degree of enhanced pathogenicity of A. hydrophila was noticed with increased mortalities (84.2%) in comparison to other groups. The current study shows a declining pattern in RBC, PCV and Hb values with the degree of parasite infestation without co-infection groups. Moreover, in the T8 group, exposure of a sub-lethal dose of bacteria resulted in a drastic reduction of the recorded parameters. Furthermore, a decreased value for WBC, monocyte and neutrophil was found in higher parasite group co-infected with a sub-lethal dose of bacteria relative to other co-infected groups during the experimental period. Also, a decrease in innate immune parameters and antioxidative stress enzymes were observed in the T8 group compared to T7 and T2 groups throughout the trial period. These findings indicate that a rise in the dose of Argulus infection improves A. hydrophila colonization in goldfish and contributes to suppression of the innate immune system and increased mortality.

Nonylphenol exposure in Labeo rohita (Ham.): Evaluation of behavioural response, histological, haematological and enzymatic alterations.

The impact of acute and chronic exposure of nonylphenol (NP) on behaviour, histopathology, haematology and biochemical parameters of Labeo rohita (Hamilton, 1822) was investigated in the current study. The 96 h LC50 of NP for L. rohita was estimated to be 0.548 mg L-1. Acute toxicity of NP induced several behavioural alternations. Further, sub-lethal NP exposure for a period of sixty days to 1/10th (0.0548 mg L-1), 1/15th (0.0365 mg L-1) and 1/20th (0.0274 mg L-1) of 96 h LC50 resulted a reduction in total erythrocyte count and haemoglobin content whereas the total leukocyte count was observed to increase significantly. Among the biochemical parameters, blood glucose level increased, but there was significant decrease in total serum protein, albumin and globulin level. Significant alterations occurred in the histological architecture of gill tissue in NP exposed groups. The catalase and superoxide dismutase activity in gill tissues were elevated significantly while the concentration dependent inhibition of acetylcholinesterase activity was observed on 20th, 40th and 60th day of NP exposure. An increased glutathione-S-transferase activity in gill tissue was also observed in NP exposed groups. The present ecotoxicological study provides a reliable indication for the obligation to control the use and safe disposal of NP.

Histopathology of head kidney tissues in challenged rohu, Labeo rohita Hamilton after vaccinating with Aeromonas hydrophila antigens.

The study was conducted to evaluate the vaccination effects on rohu, Labeo rohita head kidney tissues while assessing the vaccine efficacy of Aeromonas hydrophila antigens. Six acclimatized rohu groups were immunized with three antigenic formulations (outer membrane proteins, somatic and whole-cell antigen) @ 200 µg/fish and also with equal volume of Freund's incomplete adjuvant (FIA), separately. Simultaneously, two non-vaccinated groups, i.e., injected with FIA (100µl), normal saline solutions (0.85%) and one control without injection were maintained for 28 days. All rohu were challenged with median lethal dose of A. hydrophila (2.85 × 106 cells/rohu) intraperitoneally. After 7 days, highest cumulative mortality (%) of ˃88% was found for all non-vaccinated groups. During histopathological observations in head kidney tissues of all treatment and control groups, numerous histopathological changes in the nephritic cells like mild loss of typical tubular epithelial lining, necrosis, thickening of renal epithelial lining, haemorrhages, inflammation, distorted and widening of the lumen with vacuolated surrounding and the constricted lumen of nephritic tubules were noticed for vaccinated rohu in contrast to non vaccinated groups before A. hydrophila challenge. In case of all non-vaccinated fish, including control, extensive degenerated and necrotized head kidney tissues were observed, whereas it was least observed in vaccinated rohu after 7 days A. hydrophila challenge. Results suggest that OMPs antigen along with FIA was the premier vaccine approach for improving resistance to Aeromonas disease and reduce mortality in rohu. Similarly, vaccination with all three antigenic formulations, preferably when applied along with FIA, can effectively protect the head kidney against A. hydrophila infection.

Triclosan exposure induces varying extent of reversible antimicrobial resistance in Aeromonas hydrophila and Edwardsiella tarda.

Triclosan (TCS) is a biocide commonly used in household and personal care items to prevent the microbial growth and is currently considered as an emerging pollutant. It has a ubiquitous distribution which can substantially contribute towards antimicrobial resistance. The present study was designed to evaluate the effect of different concentrations of TCS exposure on the antibiotic sensitivity of aquatic bacteria. Aeromonas hydrophila ATCC® 49140™ and Edwardsiella tarda ATCC® 15947™ exposed to TCS for short (30 min) and long duration (serial passages). The agar-disc diffusion assay during the serial passages of TCS exposure and subsequent exposure withdrawal showed clinically insignificant changes in the zone of inhibition for six selected antibiotics in both bacterial strains at all exposure concentrations. Four folds concentration-dependent increase in the minimum inhibitory concentrations (MICs) of TCS was observed in both the strains following TCS exposure. Similarly, a concentration-dependent increase in the MICs of oxytetracycline (OTC) up to 4 folds in A. hydrophila, and up to 8 folds in E. tarda, was also documented during the TCS exposure. In all the cases, withdrawal of TCS exposure effectively reduced the MICs of TCS and OTC in blank passages suggesting a decline in acquired resistance. The frequencies of mutation during 30 min TCS exposure for E. tarda and A. hydrophila ranged between >10-6 and 10-7 levels. Nevertheless, the TCS exposure did not cause any detectable mutation on the fabV gene of A. hydrophila indicating that the TCS may elicit phenotypic adaptation or other resistance mechanism. Although the reduction in MICs due to exposure withdrawal did not restore the bacterial susceptibility up to the initial level, the study proved that the reduced TCS use could significantly help reduce the antimicrobial-resistance and cross-resistance in pathogenic bacteria.

Triclosan toxicity alters behavioral and hematological parameters and vital antioxidant and neurological enzymes in Pangasianodon hypophthalmus (Sauvage, 1878).

Triclosan and its metabolites are detected in a diverse aquatic environment and are major concerns for various aquatic organisms. The present study investigated the impact of acute and sub-lethal exposure of triclosan on behaviour, activities of acetylcholinesterase and selected antioxidant enzymes, haematological and serum gas-electrolyte parameters of Pangasianodon hypophthalmus. The 96 h LC50 of triclosan for P. hypophthalmus was estimated as 1458 µg L-1. Further, sub-lethal triclosan exposure to 1/15th (97 µg L-1), 1/10th (145 µg L-1) and 1/5th (291 µg L-1) of 96 h LC50 concentration for a period of 45 days lead to decrease in total erythrocyte count, haemoglobin content and packed cell volume of blood while total leukocyte count increased significantly (p < 0.05) as compared to control. A concentration-dependent increase in the serum chloride and decrease in partial pressure of oxygen in blood serum was noted on 45th day. An increased activity of catalase and superoxide dismutase in gill and liver tissues and inhibition of acetylcholinesterase activity in brain was observed on 15th, 30th and 45th day of exposure which was dependent on both - concentration of triclosan and duration of exposure. A significant high activity of glutathione-S-transferase in gill and liver tissue was observed in triclosan exposed groups in comparison to control during the experimental period. The study shows that long-term sub-lethal exposure of triclosan to fish can lead to several physiological alterations such as enzymatic scavenging of oxygen radicals and the normal neurological functions mediated by the enzyme acetylcholinesterase. With increasing anthropogenic activity, the study provides a convincing evidence for the necessity of a regulated use and safer disposal of triclosan to the environment.