Malachite green in food

Inhibitors of LAMP used to detect Tenacibaculum sp. strain Pbs-1 associated with black-spot shell disease in Akoya pearl oysters, and additives to reduce the effect of the inhibitors

Black-spot shell disease is an unresolved disease that decreases pearl quality and threatens pearl oyster survival. In previous studies, the bacterium Tenacibaculum sp. strain Pbs-1 was isolated from diseased Akoya pearl oysters Pinctada fucata, and a rapid, specific, and sensitive loop-mediated isothermal amplification (LAMP) assay for detecting this pathogen was established. This technology has considerable potential for routine diagnosis of strain Pbs-1 in oyster hatcheries and/or pearl farms; therefore, it is vital to identify substances in environmental samples that might inhibit LAMP and to find additives that can reduce the inhibition. In this study, we investigated the effects of six chemicals or proteins, otherwise known as conventional PCR inhibitors, on LAMP, using the DNA of strain Pbs-1 as template: humic acid, urea, iron (III) chloride hexahydrate, melanin, myoglobin, and Ethylenediamine-N,N,N',N'-tetraacetic acid, disodium salt, dihydrate (EDTA; pH 6.5). Next, to reduce the effects of identified inhibitors, we tested the addition of bovine serum albumin (BSA) or T4 gene 32 protein (gp32) to the LAMP assay. When 50 ng of DNA template was used, 4 ng/μL of humic acid, 0.05% melanin, and 10 mM of EDTA (pH 6.5) inhibited the LAMP reaction, whereas myoglobin, urea, and FeCl3 had no effect. When 50 pg of DNA template was used, 4 ng/μL of humic acid, 0.05% melanin, 4 μg/μL of myoglobin, 10 μg/μL of urea, and 10 mM of EDTA inhibited the LAMP reaction. Thus, it was shown that the gene-amplification inhibitory effect of melanin, humic acid, and urea could be reduced by adding BSA or gp32 to the LAMP reaction mixture. This technique could be applied as part of a protocol to prevent mass mortalities of pearl oysters; moreover, the results enhance our knowledge about substances that inhibit LAMP and methods to reduce the inhibition, which have rarely been reported.

Distribution and Probabilistic Risk Assessment of Antibiotics, Illegal Drugs, and Toxic Elements in Gastropods from Southeast China

We investigated fourteen antibiotics, three illegal drugs, and two toxic elements in commercially available gastropods from southeast China. The data revealed high detection frequencies (DFs) for florfenicol (61.32%), florfenicol amine (47.33%), and thiamphenicol (39.88%), with maximum concentrations of 1110, 2222, and 136 μg/kg wet weight (ww), respectively. The DFs of illegal drugs were 3.54% for leucomalachite green and 0.3% for chloramphenicol. The average levels of Cd and As were 1.17 and 6.12 mg/kg ww, respectively. All chemicals presented diverse DFs in different sampling months. The highest DFs of florfenicol, florfenicol amine, and thiamphenicol were in July. The health risk assessment showed that targeted hazard quotients (THQs) of antibiotics, Cd, and As for children, teens, and adults were all less than one. Notably, the toxic elements (Cd and As) were identified as the primary health risk in gastropods, contributing to over 90% of the total THQs.

An account of the occurrence of residues from veterinary drugs and contaminants in animal-derived products: a case study on Brazilian supply chains

Brazil plays an important role in ensuring its position on the international market by assuring high food safety standards for its products, and all products should meet the requirements for residues from veterinary drugs and contaminants in animal products. Statutory monitoring provides insights into the compliance of the Brazilian industry regarding these legal requirements. The objective of this study was to provide insight into the safety of Brazilian animal products by reporting the occurrence of residues from veterinary drugs and contaminants according to an analysis of an 11-year report published by the Brazilian Ministry of Agriculture, Livestock and Food Supply (MAPA). Between 2010 and 2021, 166,647 samples from animal-derived products were analyzed in Brazil, and 624 of those samples were non-compliant (0.37%) exceeding maximum residue limits (>MRLs) or showed the presence of prohibited substances. The most common types of substances found in the non-compliant samples were heavy metals, parasiticides, and antimicrobials, accounting for 82% of all documents from the MAPA. Among Brazilian products, the challenge related to occurrence of substances varied across the food supply chain, with highest incidence rates observed in the fish chain, followed by eggs, milk, equids, sheep/goat, honey, bovine, swine, and broilers chains in decreasing order. Considering the type of substance, heavy metals were found to be more prevalent in fish products, mainly arsenic in wild fish. The prevalence of contaminants and heavy metals decreased, while that of veterinary drugs increased in Brazilian products from 2010 to 2021. From these results, it can be concluded that the number of accidental incidents including those associated with environmental contaminants decreased over the last decade, opposed to those involving human adversaries and deliberate illegal actions, such as the abuse of veterinary drugs, increased. Future monitoring plans need to take this paradigm shift into account.

Evaluating the persistence of malachite green residues in tilapia and pacu fish

Although banned in food-producing animals, residues of malachite green (MG) and its primary metabolite, leucomalachite green (LMG), have been found in fish due to illegal use in aquaculture and the release of industrial wastewater, which represent a serious risk to food and environmental securities. This study aimed to investigate the residue depletion profile of MG and LMG in edible tissues of Nile tilapia (Oreochromis niloticus) and pacu (Piaractus mesopotamicus) cultured simultaneously under the same environmental conditions to support control measures in case of abuse. An analytical method involving QuEChERS sample preparation and liquid chromatography coupled to tandem mass spectrometry was developed, validated, and applied to quantify MG and LMG residues in fish fillets from two depletion experiments after treatment by immersion bath (MG at 0.10 mg L-1 for 60 min). During the experiment, the average water temperature was 30 ºC, while the pH was 6.9. The method is selective, precise (CV = 0.4 - 22%) and accurate (recovery 92 - 114%). The limits of detection and quantification are 0.15 and 0.5 ng g-1, respectively. In both species, the sum of MG and LMG residues were quantified up to the 32nd day post-exposure, and the concentrations were significantly higher in the pacu fillets (up to 3284 ng g-1) than in Nile tilapia (up to 432 ng g-1). The sums of MG and LMG residues were below 2 ng g-1 at 44 days and 342 days for Nile tilapia and pacu, respectively - the Minimum Required Performance Limit (MRPL) for analytical methods intended to monitor forbidden substances in food according to old European Commission guidelines. The persistence of MG residues in pacu may be attributed to its higher lipid content, which favors the accumulation of the non-polar metabolite LMG. These results provide insights into the concern about human, animal, and environmental health risks resulting from unauthorized use or aquatic contamination by industrial wastewater containing MG residues.

Malachite green and leucomalachite green in fish: a global systematic review and meta-analysis

Malachite green (MG), an antibiotic with antifungal activity, is illegally used in aquaculture. Given that this chemical is teratogenic and mutagenic, abstinence from intake seems to be a need for public safety. The goal of this systematic review and meta-analysis was to determine the global contamination of fishes by MG and its reduced metabolite, leucomalachite green (LMG), in a number of marine and farmed fish species. For literature published prior to January 2022, several databases (Web of Science, PubMed, and Scopus) were investigated. In total, 20 publications (10 countries, 724 samples) achieved the criteria for inclusion. The overall average MG and LMG concentrations were 0.48 (95% CI: 0.47, 0.49 µg kg^-1) and 0.59 (95% CI: 0.39, 0.79 µg/kg^-1), respectively. Eel (M. albus) 15.50 (95% CI: (14.39, 45.39 µg kg^-1) and eel (A. anguilla) 4.46 (95% CI: 1.23, 7.69 µg kg^-1) had the greatest contamination of MG and LMG, according to the effect size, respectively. Warm-water fish had a concentration of 2.591 (95% CI: 2.25, 2.93 µg kg^-1) while cold-water fish had a concentration of 1.55 (95% CI: 0.25, 2.84 µg kg^-1). Fish containing medium-fat level of 1.86 (95% CI: 1.27, 2.44 µg kg^-1) and high-fat content of 1.10 (95% CI: 0.93, 1.26 µg kg^-1) had accumulate MG and LMG in their tissues, respectively. As a result, total MG observed in countries including China, Iran, and the Netherlands was higher than authorized (2 µg kg^-1). The toxicity of MG and LMG demands more monitoring, especially in countries where these chemicals' residues are significant.

Control of parasitic diseases in aquaculture

Finfish aquaculture in freshwater and marine environments is continuously expanding globally, and the potential for a substantial further increase is well documented. The industry is supplying fish products for human consumption to the same extent as capture fisheries, and new fish species for domestication are still being selected by the industry. The challenge faced by all aquacultured species, classical and novel, is the range of pathogens associated with each new fish type. A fish host in its natural environment carries a series of more or less specific parasites (specialists and generalists). Some of these show a marked ability to propagate in aquaculture settings. They may then elicit disease when infection intensities in the confined aquaculture environment reach high levels. In addition, the risk of transmission of parasites from aquaculture enterprises to wild fish stocks adds to the parasitic challenge. Control programmes of various kinds are needed and these may include chemotherapeutants and medicines as the farmer's first and convenient choice, but mechanical, biological, immunological and genetic control methods are available solutions. New methods are still to be developed by scrutinizing the life cycle of each particular parasite species and pin-pointing the vulnerable stage to be targeted. As parasites exhibit a huge potential for adaptation to environmental changes, one must realize that only one approach rarely is sufficient. The present work therefore elaborates on and advocates for implementation of integrated control strategies for diseases caused by protozoan and metazoan parasites.

Oxidative Stress and Toxico-Pathic Branchial Lesions in Cyprinus carpio Exposed to Malachite Green

Gill is the frontier tissue to come in direct contact with aquatic toxicants. Malachite green (MG) commercial textile dye was assessed for its impact on the gill cytoarchitecture. Cyprinus carpio were exposed to 0.087 and 0.146 mg/L of MG for 60 days. The tissue was processed, and HE stained slides revealed histo-pathic lesions such as lamellar curling, edema, necrosis, telangiectasia, aneurysm, and vacuolization. Scanning electron microscopy reported aberrations in lamellae and microridges of the epithelium. At the cellular level, transmission electron microscopy exhibited nuclear alterations in form of pyknosis and mitochondrial swelling followed by cristolysis. Pillar cells displayed cytoplasmic vacuolization and leukocyte infiltration, and goblet cell containing varied shaped and density mucous globules. The biochemical analysis supported the ultrastructural alterations and showed a negative impact of MG on the antioxidative enzymes (CAT, SOD, GSH), while levels of MDA were found to be significantly elevated. Thereby, concluding MG induced branchial toxicity in the fish.

Comparative Therapeutic Effects of Natural Compounds Against Saprolegnia spp. (Oomycota) and Amyloodinium ocellatum (Dinophyceae)

The fish parasites Saprolegnia spp. (Oomycota) and Amyloodinium ocellatum (Dinophyceae) cause important losses in freshwater and marine aquaculture industry, respectively. The possible adverse effects of compounds used to control these parasites in aquaculture resulted in increased interest on the search for natural products with antiparasitic activity. In this work, eighteen plant-derived compounds (2′,4′-Dihydroxychalcone; 7-Hydroxyflavone; Artemisinin; Camphor (1R); Diallyl sulfide; Esculetin; Eucalyptol; Garlicin 80%; Harmalol hydrochloride dihydrate; Palmatine chloride; Piperine; Plumbagin; Resveratrol; Rosmarinic acid; Sclareolide; Tomatine, Umbelliferone, and Usnic Acid) have been tested in vitro. Sixteen of these were used to determine their effects on the gill cell line G1B (ATCC®CRL-2536™) and on the motility of viable dinospores of Amyloodinium ocellatum, and thirteen were screened for inhibitory activity against Saprolegnia spp. The cytotoxicity results on G1B cells determined that only two compounds (2′,4′-Dihydroxychalcone and Tomatine) exhibited dose-dependent toxic effects. The highest surveyed concentrations (0.1 and 0.01 mM) reduced cell viability by 80%. Upon lowering the compound concentration the percentage of dead cells was lower than 20%. The same two compounds revealed to be potential antiparasitics by reducing in a dose-dependent manner the motility of A. ocellatum dinospores up to 100%. With respect to Saprolegnia, a Minimum Inhibitory Concentration was found for Tomatine (0.1 mM), Piperine and Plumbagin (0.25 mM), while 2′,4′-Dihydroxychalcone considerably slowed down mycelial growth for 24 h at a concentration of 0.1 mM. Therefore, this research allowed to identify two compounds, Tomatine and 2′,4′-Dihydroxychalcone, effective against both parasites. These compounds could represent promising candidates for the treatment of amyloodiniosis and saprolegniosis in aquaculture. Nevertheless, further in vitro and in vivo tests are required in order to determine concentrations that are effective against the considered pathogens but at the same time safe for hosts, environment and consumers.

Development of a multi-class method to determine nitroimidazoles, nitrofurans, pharmacologically active dyes and chloramphenicol in aquaculture products by liquid chromatography-tandem mass spectrometry

LC-MS/MS method was developed for the efficient identification and quantification of 21 banned substances including various nitroimidazoles, nitrofurans, pharmacologically-active dyes and chloramphenicol, respectively in aquaculture products. The sample preparation was started by acid-treatment with 2-nitrobenzaldehyde (NBA) to liberate matrix-bound residues of nitrofurans. A modified QuEChERS method was optimized for the extraction and clean-up of the target analytes. The metabolites of the four conventional nitrofurans (nitrofurantoin, furazolidone, nitrofurazone and furaltadone) and of three other nitrofurans (nifursol, nifuroxazide, and nitrovin), and an underivatizable nitrofuran (nifurpirinol) were simultaneously detected. Furthermore, 21 banned substances were quantified by LC-MS/MS with ESI using one single injection. To evaluate and validate the performance of the method, the criteria of the Decision (EC) no 2002/657 were applied. Decision limit (CCα) of target analytes ranged 0.067-1.655 μg/kg in aquaculture products. The recovery ranged 77.2%-125.6%, and the relative standard deviations of inter-day analyses (RSD) were less than 25%.

In vitro activity of chemicals and commercial products against Saprolegnia parasitica and Saprolegnia delica strains

Oomycetes of the genus Saprolegnia are responsible for severe economic losses in freshwater aquaculture. Following the ban of malachite green in food fish production, the demand for new treatments pushes towards the selection of more safe and environment-friendly products. In the present work, in vitro activity of ten chemicals and three commercial products was tested on different strains of Saprolegnia, using malachite green as reference compound. The compounds were screened in agar and in water to assess the minimum inhibitory concentration (MIC) and the minimum lethal concentration (MLC), respectively. Two strains of Saprolegnia parasitica and one isolate of Saprolegnia delica were tested in triplicate per each concentration. Among tested chemicals, benzoic acid showed the lowest MIC (100 ppm) followed by acetic acid, iodoacetic acid and copper sulphate (250 ppm). Sodium percarbonate was not effective at any tested concentration. Among commercial products, Virkon^™ S was effective in inhibiting the growth of the mycelium (MIC = MLC = 1,000 ppm). Actidrox® and Detarox® AP showed MIC = 5,000 and 1,000 ppm, respectively, while MLCs were 10-fold lower than MICs, possibly due to a higher activity of these products in water. Similarly, a higher effectiveness in water was observed also for iodoacetic acid.

Liquid Chromatography Analysis of Common Nutritional Components, in Feed and Food

Food and feed laboratories share several similarities when facing the implementation of liquid-chromatographic analysis. Using the experience acquired over the years, through application chemistry in food and feed research, selected analytes of relevance for both areas were discussed. This review focused on the common obstacles and peculiarities that each analyte offers (during the sample treatment or the chromatographic separation) throughout the implementation of said methods. A brief description of the techniques which we considered to be more pertinent, commonly used to assay such analytes is provided, including approaches using commonly available detectors (especially in starter labs) as well as mass detection. This manuscript consists of three sections: feed analysis (as the start of the food chain); food destined for human consumption determinations (the end of the food chain); and finally, assays shared by either matrices or laboratories. Analytes discussed consist of both those considered undesirable substances, contaminants, additives, and those related to nutritional quality. Our review is comprised of the examination of polyphenols, capsaicinoids, theobromine and caffeine, cholesterol, mycotoxins, antibiotics, amino acids, triphenylmethane dyes, nitrates/nitrites, ethanol soluble carbohydrates/sugars, organic acids, carotenoids, hydro and liposoluble vitamins. All analytes are currently assayed in our laboratories.

Rapid Analysis of Illegal Cationic Dyes in Foods and Surface Waters Using High Temperature Direct Analysis in Real Time High-Resolution Mass Spectrometry

A high temperature desorption (HTD) direct analysis in real time-high-resolution mass spectrometric (DART-HRMS) method was developed for the rapid analysis of four banned cationic dyes. Rhodamine B is used to dye foods, while malachite green, crystal violet, and methylene blue are added to fishponds as antimicrobials. A simple induced phase separation extraction was used to pretreat samples. The DART-HRMS method employed two temperature steps, i.e., 200 °C for drying, purification, and enrichment of sample solution and 500 °C for thermal desorption and ionization of analytes. The calibration curves of dyes in the range of 50-2000 ng/mL were linear using deuterated malachite green as an internal standard. The LODs vary for all analytes between 0.1 and 30 ppb depending on the matrix and experimental conditions. Through analyses of real samples, two chili powders and one chili oil were found to be contaminated by rhodamine B. The concentrations were comparable with those found by an HPLC-MS/MS method.