Main Toxin Research Articles

Purified CDT toxins and a clean deletion within the CDT locus provide novel insights into the contribution of binary toxin in cellular inflammation and Clostridioides difficile infection.

Clostridioides difficile is a spore-forming pathogen and the most common cause of healthcare-associated diarrhea and colitis in the United States. Besides producing the main virulence factors, toxin A (TcdA) and toxin B (TcdB), many of the common clinical strains encode the C. difficile transferase (CDT) binary toxin. The role of CDT in the context of C. difficile infection (CDI) is poorly understood. Inflammation is a hallmark of CDI and multiple mechanisms of inflammasome activation have been reported for TcdA, TcdB, and the organism. Some studies have suggested that CDT contributes to this inflammation through a TLR2-dependent priming mechanism that leads to the suppression of protective eosinophils. Here, we show that CDT does not prime but instead activates the inflammasome in bone marrow-derived dendritic cells (BMDCs). In bone marrow-derived macrophages (BMDMs), the cell binding and pore-forming component of the toxin, CDTb, alone activates the inflammasome and is dependent on K+ efflux. The activation is not observed in the presence of CDTa and is not observed in BMDMs derived from Nlrp3-/- mice suggesting the involvement of the NLRP3 inflammasome. However, we did not observe evidence of CDT-dependent inflammasome priming or activation in vivo. Mice were infected with R20291 and an isogenic CRISPR/Cas9-generated R20291 ΔcdtB strain of C. difficile. While CDT contributes to increased weight loss and cecal edema at 2 days post infection, the relative levels of inflammasome-associated cytokines, IL-1β and IL-18, in the cecum and distal colon are unchanged. We also saw CDT-dependent weightloss in Nlrp3-/- mice, suggesting that the increased weightloss associated with the presence of CDT is not a result of NLRP3-dependent inflammasome activation. This study highlights the importance of studying gene deletions in the context of otherwise fully isogenic strains and the challenge of translating toxin-specific cellular responses into a physiological context, especially when multiple toxins are acting at the same time.

Toxicological analyses of the venoms of Nigerian vipers Echis ocellatus and Bitis arietans

BackgroundAmong the medically important snakes in Nigeria, Echis ocellatus and Bitis arietans have the most lethal venom. These venoms were classified according to the presence of snake venom metalloproteinases (SVMPs), snake venom phospholipase A2 (PLA2s), and snake venom serine proteases (SVSPs). Toxicological analyzes were performed to understand the significance of different protein families in venoms.MethodsProteins were separated from venom using column chromatography. The skin and footpad of mice were used to determine hemorrhagic and edematogenic activities. Caprine blood plasma was used to test fibrinolytic activity in vitro.ResultsThe results showed that, compared to the crude venom, the SVMP fraction induced hemorrhagic effects with a diameter of 26.00 ± 1.00 mm in E. ocellatus and 21.33 ± 1.52 mm in B. arietans. Both SVSP and SVMP had anticoagulant effects; however, the SVSP fraction had a stronger effect, with a longer anticoagulation time of 30.00 ± 3.00 min in E. ocellatus and 26.00 ± 2.00 min in B. arietans. These main venom toxins, SVMPs, SVSPs, and PLA2, were found to have edema-forming effects that were optimal at 2 h after envenomation. PLA2s had the highest edema-inducing activity, with onset 30 min after envenomation.ConclusionsGiven the importance of SVMPs in altering the integrity of the membrane structure and impairing the blood coagulation system, an antivenom that can specifically neutralize its activity could inhibit the hemorrhage effects of the venoms.

Unraveling Hematotoxicity of α-Amanitin in Cultured Hematopoietic Cells.

Amanita phalloides poisonings account for the majority of fatal mushroom poisonings. Recently, we identified hematotoxicity as a relevant aspect of Amanita poisonings. In this study, we investigated the effects of the main toxins of Amanita phalloides, α- and β-amanitin, on hematopoietic cell viability in vitro. Hematopoietic cell lines were exposed to α-amanitin or β-amanitin for up to 72 h with or without the pan-caspase inhibitor Z-VAD(OH)-FMK, antidotes N-acetylcysteine, silibinin, and benzylpenicillin, and organic anion-transporting polypeptide 1B3 (OATP1B3) inhibitors rifampicin and cyclosporin. Cell viability was established by trypan blue exclusion, annexin V staining, and a MTS assay. Caspase-3/7 activity was determined with Caspase-Glo assay, and cleaved caspase-3 was quantified by Western analysis. Cell number and colony-forming units were quantified after exposure to α-amanitin in primary CD34+ hematopoietic stem cells. In all cell lines, α-amanitin concentration-dependently decreased viability and mitochondrial activity. β-Amanitin was less toxic, but still significantly reduced viability. α-Amanitin increased caspase-3/7 activity by 2.8-fold and cleaved caspase-3 by 2.3-fold. Z-VAD(OH)-FMK significantly reduced α-amanitin-induced toxicity. In CD34+ stem cells, α-amanitin decreased the number of colonies and cells. The antidotes and OATP1B3 inhibitors did not reverse α-amanitin-induced toxicity. In conclusion, α-amanitin induces apoptosis in hematopoietic cells via a caspase-dependent mechanism.

Optimizing drug discovery for snakebite envenoming via a high-throughput phospholipase A2 screening platform.

Snakebite envenoming is a neglected tropical disease that causes as many as 1.8 million envenomings and 140,000 deaths annually. To address treatment limitations that exist with current antivenoms, the search for small molecule drug-based inhibitors that can be administered as early interventions has recently gained traction. Snake venoms are complex mixtures of proteins, peptides and small molecules and their composition varies substantially between and within snake species. The phospholipases A2 (PLA2) are one of the main pathogenic toxin classes found in medically important viper and elapid snake venoms, yet varespladib, a drug originally developed for the treatment of acute coronary syndrome, remains the only PLA2 inhibitor shown to effectively neutralise venom toxicity in vitro and in vivo, resulting in an extremely limited drug portfolio. Here, we describe a high-throughput drug screen to identify novel PLA2 inhibitors for repurposing as snakebite treatments. We present method optimisation of a 384-well plate, colorimetric, high-throughput screening assay that allowed for a throughput of ∼2,800 drugs per day, and report on the screening of a ∼3,500 post-phase I repurposed drug library against the venom of the Russell's viper, Daboia russelii. We further explore the broad-spectrum inhibitory potential and efficacy of the resulting top hits against a range of medically important snake venoms and demonstrate the utility of our method in determining drug EC50s. Collectively, our findings support the future application of this method to fully explore the chemical space to discover novel PLA2-inhibiting drugs of value for preventing severe pathology caused by snakebite envenoming.

Risk characteristics of shellfish toxins in Mytilus unguiculatus around the Zhoushan Islands, East China Sea

The Zhoushan Islands, are an important area for Mytilus unguiculatus aquaculture, and are threatened by potentially harmful algal blooms. However, a full understanding of the risks posed by their toxin residues is still lacking. M. unguiculatus samples were collected from the area between 2020 and 2021 and analyzed for their toxin profiles to assess the contamination status of shellfish toxins. The main toxins detected were the paralytic shellfish toxins (PSTs), gymnodimine (GYM), and domoic acid (DA). Nine PSTs components were detected, the dominant ones being C1, C2, and GTX5, with an overall detection rate of 85.7 %. The detection rate of DA was 55.05 %, and GYM was detected in all samples. The toxin levels in the samples were significantly lower than the European Union regulatory limits, but toxin contamination was generally universal.

Proteome analysis of Daboia russelii venom, a medically important snake from the Indian sub-continent

Daboia russelii is a category-I medically important snake throughout the Indian sub-continent contributing to majority of snakebite incidences in this part of the world. As such, extensive studies on its venom composition and search of efficient and appropriate interventions for its treatment become crucial. In this study, the proteome of Daboia russelii venom from Tanore, Rajshahi, Bangladesh was profiled using a combination of chromatographic and mass spectrometric techniques. A total of 37 different proteins belonging to 11 different snake venom protein families were detected. Proteomics analysis revealed the presence of major phospholipase A2 toxins. Daboiatoxin (both A and B subunits), the main lethal PLA2 toxin in the venom of Daboia siamensis (Myanmar viper) which is neurotoxic, myotoxic and cytotoxic was detected. Presence of Daboxin P, which is a major protein in the venom of Indian Daboia russelii with strong anticoagulant activity, was also observed. Inconsistent distribution of such lethal toxins in the venom of same species calls for more investigations of snake venoms from lesser explored regions and formulation of better alternatives to the current antivenom therapy for efficient treatment.

A Comparison between SARS-CoV-2 and Gram-Negative Bacteria-Induced Hyperinflammation and Sepsis.

Sepsis is a life-threatening condition caused by the body's overwhelming response to an infection, such as pneumonia or urinary tract infection. It occurs when the immune system releases cytokines into the bloodstream, triggering widespread inflammation. If not treated, it can lead to organ failure and death. Unfortunately, sepsis has a high mortality rate, with studies reporting rates ranging from 20% to over 50%, depending on the severity and promptness of treatment. According to the World Health Organization (WHO), the annual death toll in the world is about 11 million. One of the main toxins responsible for inflammation induction are lipopolysaccharides (LPS, endotoxin) from Gram-negative bacteria, which rank among the most potent immunostimulants found in nature. Antibiotics are consistently prescribed as a part of anti-sepsis-therapy. However, antibiotic therapy (i) is increasingly ineffective due to resistance development and (ii) most antibiotics are unable to bind and neutralize LPS, a prerequisite to inhibit the interaction of endotoxin with its cellular receptor complex, namely Toll-like receptor 4 (TLR4)/MD-2, responsible for the intracellular cascade leading to pro-inflammatory cytokine secretion. The pandemic virus SARS-CoV-2 has infected hundreds of millions of humans worldwide since its emergence in 2019. The COVID-19 (Coronavirus disease-19) caused by this virus is associated with high lethality, particularly for elderly and immunocompromised people. As of August 2023, nearly 7 million deaths were reported worldwide due to this disease. According to some reported studies, upregulation of TLR4 and the subsequent inflammatory signaling detected in COVID-19 patients "mimics bacterial sepsis". Furthermore, the immune response to SARS-CoV-2 was described by others as "mirror image of sepsis". Similarly, the cytokine profile in sera from severe COVID-19 patients was very similar to those suffering from the acute respiratory distress syndrome (ARDS) and sepsis. Finally, the severe COVID-19 infection is frequently accompanied by bacterial co-infections, as well as by the presence of significant LPS concentrations. In the present review, we will analyze similarities and differences between COVID-19 and sepsis at the pathophysiological, epidemiological, and molecular levels.

Proteomic characteristics of six snake venoms from the Viperidae and Elapidae families in China and their relation to local tissue necrosis

Patients envenomed by snakes from the Viperidae and Elapidae families in China often have varying degrees of local tissue necrosis. Due to the relative clinical characteristics of local tissue necrosis and ulceration following envenoming, this study has analyzed the proteome of six snake venoms from the Viperidae and Elapidae family, and the toxin profiles of each snake were compared and correlated with the clinical manifestations that follow cytotoxic envenoming. Deinagkistrodon acutus and Naja atra envenomation induce severe ulceration, which is absent in Bungarus multicinctus envenomation and mild in the other three vipers. It is interesting to note that the proportion of c-type lectins (CTL) (20.63%) in Deinagkistrodon acutus venom was relatively high, which differs from the venom of other vipers. In addition, three-fingered toxin (3FTx) (2.15%) is present in the venom of Deinagkistrodon acutus, but has not been detected in the remaining three vipers. Snake venom metalloprotease (SVMP) (34.4%–44.7%), phospholipase A2 (PLA2) (9.81%–40.83%), and snake venom serine protease (SVSP) (9.44%–16.2%) represent the most abundant families of toxin in Viperidae venom. The Elapidae venom proteome was mainly composed of neurotoxins and cytotoxins, including 3FTx (39.28%–60.08%) and PLA2 (8.24%–58.95%) toxins, however, the proportion of CRISPS (26.36%) in Naja atra venom was relatively higher compared to Bungarus multicinctus venom. Significant differences in SVMP, SVSP, and 3FTx expression levels exist between the Viperidae and the Elapidae family. The main toxins responsible for the development of tissue necrosis and ulcerations following Viperidae envenoming are hematotoxins (SVSMP, SVSP) and myotoxins (PLA2). Deinagkistrodon acutus venom contains high levels of CTL and traces of 3FTx, leading to more severe local necrosis. However, Naja atra venom can also cause severe local necrosis through the effects of myotoxin (3FTx, CRISP, PLA2). Bungarus multicinctus venom does not contain myotoxins, resulting in pure systemic neurological manifestations no obvious necrosis of local tissue in patients.

What happens in the shadows - Influence of seasonal and non-seasonal dynamics on domoic acid monitoring in the Monterey Bay upwelling shadow

Domoic acid produced by toxigenic Pseudo-nitzschia species is the main toxin threat from harmful algal blooms in Monterey Bay and the larger California Current region on the West Coast of the United States. Toxin monitoring in Monterey Bay includes a long-running time series of weekly measurements of domoic acid from water samples, sentinel mussels, and solid phase adsorption toxin tracking (SPATT) at the Santa Cruz Municipal Wharf (SCW). The SCW sampling site is unusual because of its position in the Monterey Bay upwelling shadow in the north bay. The upwelling shadow circulation pattern has been previously characterized as a bloom incubator for dinoflagellates, but it has not yet been analyzed in the context of long-term monitoring methods. In data collected from the SCW from 2012 - 2020, domoic acid from water samples and sentinel mussels had a different temporal distribution than domoic acid from SPATT. Here we explore the discrepancy through a seasonal and non-seasonal analysis including physical oceanography of the region. Results show that domoic acid from water samples and sentinel mussels are related to seasonal upwelling and Pseudo-nitzschia blooms. Domoic acid monitored by SPATT, on the other hand, is correlated to anomalous upwelling and warmer than usual temperatures during the relaxation season. This work builds on previous analyses of the SCW time series and contributes to understanding of the circulation of dissolved toxin in the environment. Results lend rationale for the continuation of rigorous domoic acid monitoring in Monterey Bay and encourage stakeholders to consider local physical dynamics when interpreting toxin monitoring data.

Integrated analysis of marine biotoxins and contaminants of emerging concern in bivalve mollusks from Santa Catarina, Brazil

Santa Catarina is the main producer state of oysters and mussels in Brazil, reaching 98 % of national production. To assure the safety of bivalve mollusks production, control programs of marine biotoxins (MBs) have been continuously performed. Herein, the co-occurrence of MBs and contaminants of emerging concern (CECs) in oyster and mussels from the main production sites of Santa Catarina was reported, covering 178 compounds. Samples of wild and non-cultivated oysters and mussels were also assessed. Chemometric tools were used to evaluate and optimize several sample preparation techniques such as solid-liquid, ultrasound assisted, and pressurized liquid extraction. The optimized protocol was based on ultrasound assisted extraction followed by liquid chromatography coupled to tandem mass spectrometry. The results showed the incidence of several CECs and MBs. In the case of MBs, all results were below the regulatory limits for both cultivated and non-cultivated samples. Wild mollusks have shown a higher number of compounds. Regarding CECs, the more frequent compounds were caffeine, diclofenac, meloxicam, and sertraline. Domoic acid and okadaic acid were the main toxins detected. The results highlighted the need of monitoring for MBs and the potential of oyster and mussels as sentinel organisms to risk analysis of CECs in coastal regions. To the best of our knowledge, this is the first method to describe a simultaneous sample preparation and analysis of CECs and MBs in bivalve mollusks, as well as the first report of meloxicam and florfenicol in mussels and oysters.

Literature review on Crotalus durissus terrificus toxins: From a perspective of structural biology and therapeutic applications.

The venom of Crotalus durissus terrificus, as well as its fractions, has intrigued research groups worldwide who are working to isolate, characterize, and find possible biotechnological applications. A number of studies have elucidated that these fractions and their derivatives possess pharmacological properties, which can enable the development of new drug prototypes with anti-inflammatory, antinociceptive, antitumor, antiviral, and antiparasitic applications. This review presents a systematic study on Crotalus durissus terrificus, the most notable crotalid subspecies in South America, focusing on the composition, toxicological mechanisms, structural aspects, and applications of the main venom toxins (convulxin, gyroxin, crotamine, crotoxin, and their subunits). The authors have found that research on this snake and its toxins is still an area of focus, despite that almost a century has passed since the isolation of crotoxin. Several applications of these proteins in the development of novel drugs and bioactive substances have also been demonstrated.

Ginger blotches on Agaricus bisporus due to monoacetylphloroglucinol production by the pathogen Pseudomonas 'gingeri'.

Agaricus bisporus is the most widely cultivated and consumed mushroom worldwide. Pseudomonas 'gingeri' is the only pathogenic causative agent of ginger blotch in A. bisporus. Current research on mushroom pathogenic biotoxins is limited to P. tolaasii, which causes brown blotch, while understanding of P. 'gingeri' is lacking, therefore identifying the toxins produced by P. 'gingeri' and evaluating their toxicity on A. bisporus is essential for understanding its pathogenic mechanisms. A pathogenic bacterium isolated from fruiting bodies of A. bisporus with ginger blotch was identified as P. 'gingeri', and its main toxin identified as 2', 4', 6'-trihydroxyacetophenone monohydrate, also known as monoacetylphloroglucinol (MAPG). Its first known extraction from a mushroom pathogen is reported here. MAPG at 250 μg/mL significantly inhibited the host's mycelial growth, increased branching, caused the structure to become dense and resulted in folds appearing on the surface. An MAPG concentration of 750 μg/mL MAPG led to mycelial death. P. 'gingeri' had high MAPG production in medium containing 0.1 mol/L of either glucose or mannitol (4.30 and 1.85 μg/mL, respectively), and mycelia were inhibited by 69.6% and 41.1%, respectively. The MAPG content was significantly lower in other carbon source media. This work provides a detailed description of the structure and virulence of the P. 'gingeri' biotoxin, which has implications for understanding its pathogenic mechanism and for exploring precise control strategies for A. bisporus ginger blotch disease, such as the development of MAPG inhibitory factors. © 2023 Society of Chemical Industry.

Determination of ptaquiloside in ten species of Pteris in northwestern Argentina

The toxic effect of ferns of the genus of Pteris in bovines is caused by ptaquiloside, the main carcinogenic toxin. In this study, ten species of Pteris fern in different phenologic stages and plant conditions were collected in northwest Argentina. The phytochemical analysis showed the presence of Pt in the recent collected samples (adults and young plants) but not in the herbarium specimens. The results show a great variation of Pt concentration that depends on the phenologic stage, plant condition, and collection site. Pt was measured in 6–4326 μg/g concentration, with a mean concentration of 644 μg/g. No Pt was detected in eight species of Pteris collected from herbarium samples; such results may be a false negative. It is important to notice that analysis of herbarium samples for Pt may not be a reliable method to determine its presence. It is important to further understand the potential toxicity caused by these ferns because of their effect on animals, public health, and the environment.

The Dynamic Nature of a Static Headspace Above Frozen Leaf Biomass From a Toxic Brazilian Plant

A static headspace method of sampling coupled to a conventional instrumental analytical probe, gas chromatography mass spectrometry (GCMS), has been applied to examine the volatile fraction above leaf tissue from Palicourea marcgravii, a toxic Brazilian plant that causes sudden death in livestock, and two other surrogate species (Lippia alba and Plectranthus spp.). 
 
 The unusual total ion chromatogram obtained for the plant of interest is discussed and explained by considering the “dynamic” nature of the static headspace when intact cellular biomass is present and frozen leaves are analyzed concerning the presence and production of methyl salicylate (MeSA), which is this plants main toxin.

A Metal Organic Framework-Based Light Scattering ELISA for the Detection of Staphylococcal Enterotoxin B

Enzyme-linked immunosorbent assay (ELISA) is one of the most commonly used method for the detection of staphylococcal enterotoxin B (SEB), the main protein toxin causing staphylococcal food poisoning. However, the traditional ELISA reaction needs to be stopped by sulfuric acid to obtain stable colorimetric signal, and it is easily influenced by a colored sample. In order to address this problem, a new ELISA method using zeolite imidazolate skeleton-8 metal-organic framework (ZIF-8 MOF) as a light scattering (LS) reporter for SEB detection was developed in this work. ZIF-8 MOF has the characteristics of high porosity, large specific surface area, clear pore structure, and adjustable size, which is one of the most representative MOFs constructed from Zn2+ and 2-methylimidazole (2-mIM). The 2-mIM ligand of ZIF-8 exhibited antioxidant activity and can strongly react with H2O2, which could destroy the structure of ZIF-8, resulting in the obvious decrease in LS intensity. We combined this specific reaction with the sandwich immune reaction to construct the LS ELISA method for the successful detection of SEB. This method is more reliable than commercial tests kits for the detection of colored samples, and it is simple, sensitive, and selective, and has great potential in the detection of other toxins by simply changing the corresponding recognition units.

Genome characteristics of the optrA-positive Clostridium perfringens strain QHY-2 carrying a novel plasmid type.

Clostridium perfringens is a bacterial species of importance to both public and animal health. The gene optrA is the first gene that confers resistance to the tedizolid, a last-resort antimicrobial agent in human medicine. Herein, we whole-genome sequenced and analyzed one optrA-positive C. perfringens strain QHY-2 from Tibetan sheep in Qinghai province and identified one optrA plasmid pQHY-2. The plasmid shared similar structure with the optrA-positive plasmids p2C45 and p21-D-5b previously identified in C. perfringens, demonstrating the potential horizontal transmission of the optrA plasmids among C. perfringens strains. Annotation of the optrA-positive plasmids showed optrA and erm(A) located on a segment flanked by IS element IS1216E, and fexA, optrA, and erm(A) located on a segment flanked by IS element ISVlu1, which revealed the possible dissemination mechanism. Additionally, a Tn6218-like transposon carrying aac(6')-aph(2″) and erm(B) was also detected on pQHY-2, demonstrating the transposition of Tn6218 and spread of antibiotic resistance among Clostridium bacteria. Molecular analysis indicated the optrA-positive plasmids belonged to a plasmid type distinct from the pCW3-like plasmids, pCP13-like plasmids, or pIP404-like plasmids. Further structure analysis showed they might be formed by inserting segments into plasmid pCPCPI53k-r1_1, which coexist with two pCW3-like plasmids and one pCP13-like plasmid in C. perfringens strain CPI 53k-r1 isolated from a healthy human in Finland. IMPORTANCE Antimicrobial resistance is now a global concern posing threats to food safety and public health. The pCW3-like plasmids can encode several main toxin genes and three antibiotic resistance genes (ARGs), including tetA(P), tetB(P), and erm(B), which used to be considered as the main carrier of ARGs in Clostridium perfringens. In this study, we found the optrA plasmids, which belonged to a novel plasmid type, could also harbor many other ARGs, indicating this type of plasmid might be the potential repository of ARGs in C. perfringens. Additionally, this type of plasmid could coexist with the pCW3-like plasmids and pCP13-like plasmids that encoded toxin genes associated with gastrointestinal diseases, which showed the potential threat to public health.

Major Fusarium species and mycotoxins associated with freshly harvested maize grain in Uruguay.

Fusarium species are common fungal pathogens of maize. Fusarium graminearum and Fusarium verticillioides, among others, can cause maize ear rot, and they are also mycotoxin producers. The aims of this work were to determine the frequency and diversity of Fusarium species in Uruguayan maize kernels, evaluate the toxigenic potential of the isolates, determine toxin contamination levels on freshly harvested grain, and assess the sensitivity of main Fusarium species against fungicides. Fusarium verticillioides was the most frequent species isolated, followed by Fusarium graminearum sensu stricto. Of F. verticillioides isolates studied for fumonisin production, 72% produced fumonisin B1 and 32% fumonisin B2. Considering in vitro toxin production by F. graminearum sensu stricto isolates, deoxynivalenol was the main toxin produced, followed by zearalenone and nivalenol. Fumonisins were the most frequently found toxins on freshly harvested maize samples (98% in 2018 and 86% in 2019), and also, fumonisin B1 was the toxin with highest concentration in both years studied (4860µg/kg in 2018 and 1453µg/kg in 2019). Deoxynivalenol and zearalenone were also found as contaminants. Metconazole and epoxiconazole were the most effective fungicides tested on F. verticillioides isolates. Fusarium graminearum sensu stricto isolates also were more sensitive to metconazole compared to other fungicides; nevertheless, epoxiconazole was less efficient in controlling this species. This is the first study that reports Fusarium species and mycotoxin contamination levels associated with maize grain in Uruguay. Its detection is the main step to develop management strategies in order to minimize fungal infection in maize crops.

Outbreaks of dermatopathy caused by Tephrosia noctiflora intoxication in Brazilian cattle

This study aims to update the knowledge concerning the intoxication by Tephrosia noctiflora in Brazilian cattle herds by reporting new cases of intoxication in lactating cows, their calves and bulls and highlight the epidemiology, clinical signs, pathogenesis, gross, and microscopic lesions. The morbidity and mortality of this intoxication in the farms studied was low. Gross lesions in all affected cattle consisted of dermatitis with hyperpigmentation, crusts, ulceration, erythema, and lichenification in the skin of limbs, ventral abdomen, perianal and perineal areas of lactating calves and adult cattle. Microscopically, the main lesion observed consisted of severe dermatitis with parakeratotic hyperkeratosis, papillated proliferation, and diffuse, accentuated lymphoplasmacytic inflammatory infiltrate in the epidermis and dermis. The presence of skin lesions mainly in the limbs and ventral abdomen of cattle implies the pathogenesis of intoxication is related to a primary contact dermatitis, and the occurrence of similar lesions on the skin of nursing calves reinforces this hypothesis. The putative toxins of T. noctiflora have been thought to be rotenoids. Additional work is needed to define better if these compounds are the main toxin responsible for the dermatopathy observed in these herds.

Effective Pre-Clinical Treatment of Fish Envenoming with Polyclonal Antiserum.

Envenomation by venomous fish, although not always fatal, is capable of causing damage to homeostasis by activating the inflammatory process, with the formation of edema, excruciating pain, necrosis that is difficult to heal, as well as hemodynamic and cardiorespiratory changes. Despite the wide variety of pharmacological treatments used to manage acute symptoms, none are effective in controlling envenomation. Knowing the essential role of neutralizing polyclonal antibodies in the treatment of envenoming for other species, such as snakes, this work aimed to produce a polyclonal antiserum in mice and test its ability to neutralize the main toxic effects induced by the venoms of the main venomous Brazilian fish. We found that the antiserum recognizes the main toxins present in the different venoms of Thalassophryne nattereri, Scorpaena plumieri, Potamotrygon gr. Orbignyi, and Cathorops spixii and was effective in pre-incubation trials. In an independent test, the antiserum applied immediately to the topical application of T. nattereri, P. gr orbygnyi, and C. spixii venoms completely abolished the toxic effects on the microcirculation, preventing alterations such as arteriolar contraction, slowing of blood flow in postcapillary venules, venular stasis, myofibrillar hypercontraction, and increased leukocyte rolling and adherence. The edematogenic and nociceptive activities induced by these venoms were also neutralized by the immediate application of the antiserum. Importantly, the antiserum prevented the acute inflammatory response in the lungs induced by the S. plumieri venom. The success of antiserum containing neutralizing polyclonal antibodies in controlling the toxic effects induced by different venoms offers a new strategy for the treatment of fish envenomation in Brazil.

Production profile and comparison analysis of main toxin components of Fusarium oxysporum f. sp. sesami isolates with different pathogenicity levels

Fusarium wilt is a common fungal disease in sesame caused by Fusarium oxysporum f. sp. sesami (FOS). To determine the toxin production profiles of the FOS isolates with different pathogenicity levels under various culture conditions, we assessed the content variation of fusaric acid (FA) and 9, 10-dehydrofusaric acid (9, 10-DFA) produced by the four representative FOS isolates. Results indicated that the concentration of FA reached to a maximum of 2848.66 ​μg/mL in Czapek medium, while 9, 10-DFA was mainly produced in Richard and Low-carbon Richard medium. The concentration of 9, 10-DFA on Richard culture medium varied from 0 ​μg/mL to 716.89 ​μg/mL. Of the five culture media used in this study, Czapek culture medium was the most conductive to produce FA. FA production was significantly affected by culture medium, culture time, and their interactions. Results suggest that there is no correlation between toxin production and pathogenicity level of FOS isolates. These findings provide key information for the mechanism analysis of FOS- sesame interaction and pathogen control.