Search Results (236)

Staphylococcus aureus (S. aureus) is a major cause of human morbidity and mortality worldwide. Hemolysis caused by S. aureus cytotoxins is important for the acquisition of iron and subsequent bacterial survival during infection. S. aureus can express numerous hemolysins that have been shown to target human erythrocytes. However, the relative importance of each of these for causing hemolysis during pathogenesis in humans is not clear. In this study, we have examined the hemolytic capacity of different methicillin-resistant S. aureus (MRSA) deletion mutants against human erythrocytes in suspension using two separate assays. The first assay measured hemolysis caused by extracellular factors produced by MRSA, while the second measured hemolysis following co-culture of MRSA with human erythrocytes. Results from both assays demonstrated that phenol-soluble modulin-α peptides (PSMα) play a dominant role in causing hemolysis of human erythrocytes, highlighting a prominent target for novel therapeutic strategies designed to limit S. aureus iron acquisition and survival during human disease. Full article

Helicobacter pylori (H. pylori) is a Gram-negative, spiral-shaped bacterium that colonizes the human stomach and is linked to various gastroduodenal diseases. The severity of different clinical outcomes may be determined by the combination of virulence genes. The aim of this study was to assess the combinations of the cytotoxin-associated gene A (cagA), the vacuolating cytotoxin A gene (vacA), the outer inflammatory protein A gene (oipA), and the blood group antigen-binding adhesin gene (babA2) genotypes in H. pylori and their associations with the clinical outcomes of infection in patients from Central Brazil. This cross-sectional study included 106 patients who underwent endoscopy or gastrectomy. The presence and genotypes of H. pylori were confirmed using Polymerase Chain Reaction (PCR). Gastropathies were classified according to established severity criteria. Multivariate logistic regression and Venn diagrams were used to evaluate gene combinations. In this study, the infection prevalence was 65.1%. The cagA/vacA/oipA/babA2 combination showed a protective effect against erosive esophagitis (p = 0.002), erosive duodenitis (p = 0.003), and general duodenitis (p < 0.001). No significant association was observed between this gene combination and severe gastric diseases, although a trend toward protection against gastric atrophy was noted (p = 0.049). These findings suggest that the coexistence of cagA/vacA/oipA/babA2 may play a protective role against inflammatory lesions. Further studies should explore the functional role of these gene combinations, also considering the immunogenetic profile of the host. Full article

Differences in venom within snake species can affect the efficacy of antivenom, but how this variation manifests across broad geographical scales remains poorly understood. Naja atra envenoming causes severe morbidity in China, yet whether intraspecific venom variation exists across mainland regions is unknown. We collected venom samples from seven biogeographical regions (spanning > 2000 km latitude). Venom lethality, systemic toxicity (organ damage biomarkers and coagulopathy), and histopathology of major organs were assessed. Neutralization by antivenom and label-free quantitative proteomics (LC-MS/MS) were also performed. The results revealed a non-uniform LD₅₀, with venom from Yunnan exhibiting the highest lethality (2.1-fold higher than venom from Zhejiang, p < 0.001). Commercial antivenom showed lower neutralization efficacy against the venom from the Yunnan, Guangxi, and Guangdong regions. Regarding organ damage and coagulopathy, venom from Yunnan caused severe liver damage, while venom from the Zhejiang region induced significant coagulopathy. Finally, proteomic profiles identified 175 proteins: venom from Yunnan was dominated by phospholipases, contrasting with eastern regions (Anhui/Zhejiang: cytotoxins CTXs > 30%). Venom from Guangdong contained higher levels of the weak neurotoxin NNAM2 (5.2%). Collectively, significant geographical divergence exists in Chinese Cobra venom composition, systemic toxicity, and antivenom susceptibility, driven by differential expression of key toxins. Our study provides a molecular basis for precision management of snakebites, and we call for optimized antivenom production tailored to regional variations. Full article

Helicobacter pylori is a well-established causative agent of gastritis, peptic ulcers, gastric adenocarcinoma, and primary gastric lymphoma. It colonizes the human stomach and expresses numerous virulent factors that influence disease progression. Among these factors is the cytotoxin vacA gene, which encodes the vacuolating capacity of the cytotoxin and plays a key role in the bacterium’s pathogenic potential. This study investigated the allelic diversity of the vacA among H. pylori strains infecting patients in Jordan with various gastric conditions and examined potential associations between vacA s-and m- genotypes, histopathological and endoscopic findings, and the development of gastric diseases. Gastric biopsies were collected from 106 patients at two hospitals in Jordan who underwent endoscopic examination. The collected biopsies for each patient were subjected to histopathological assessment, urease detection using the Rapid Urease Test (RUT), a diagnostic test for H. pylori, and molecular detection of the vacA gene and its s and m alleles. The histopathology reports indicated that 83 of 106 patients exhibited gastric disorders, of which 81 samples showed features associated with H. pylori infection. The RUT was positive in 76 of 106 with an accuracy of 93.8%. Real-time polymerase chain reaction (RT-PCR) targeting the 16S rRNA gene confirmed the presence of H. pylori in 79 of 81 histologically diagnosed cases as infected (97.5%), while the vacA gene was detected only in 75 samples (~95%). To explore genetic diversity, PCR-amplified fragments underwent sequence analysis of the vacA gene. The m-allele was detected in 58 samples (73%), the s-allele was detected in 45 (57%), while both alleles were not detected in 13% of samples. The predominant genotype combination among Jordanians was vacA s2/m2 (50%), significantly linked to mild chronic gastritis, followed by s1/m2 (35%) and s1/m1 (11.8%) which are linked to severe gastric conditions including malignancies. Age-and gender-related differences in vacA genotype were observed with less virulent s2m2 and s1m2 genotypes predominating in younger adults specially males, while the more virulent m1 genotypes were found exclusively in females and middle-aged patients. Genomic sequencing revealed extensive diversity within H. pylori, likely reflecting its long-standing co-evolution with human hosts in Jordan. This genetic variability plays a key role in modulating virulence and influencing clinical outcomes. Comprehensive characterization of vacA genotypic variations through whole-genome sequencing is essential to enhance diagnostic precision, strengthen epidemiological surveillance, and inform targeted therapeutic strategies. While this study highlights the significance of the vacA m and s alleles, future research is recommended in order to investigate the other vacA allelic variations, such as the i, d, and c alleles, to achieve a more comprehensive understanding of H. pylori pathogenicity and associated disease severity across different strains. These investigations will be crucial for improving diagnostic accuracy and guiding the development of targeted therapeutic strategies. Full article

Staphylococcus aureus is a Gram-positive bacterium that causes significant human morbidity and mortality. The capacity of S. aureus to cause disease is primarily attributed to an array of virulence factors produced by this pathogen that collectively overcome immune defenses and promote survival in a variety of host tissues. These include an arsenal of different cytotoxins that compromise plasma membrane integrity, with the specificity of each dependent upon the host organism and cell type. S. aureus encounters a variety of peripheral blood cell types during infection that play important roles in maintaining homeostasis and defending against microbial invasion, namely erythrocytes, thrombocytes, and leukocytes. S. aureus targets each of these cell types with specific cytotoxins to successfully establish disease. This review summarizes our current understanding of the susceptibility of different human peripheral blood cell types to each of these cytotoxins. Full article

Helicobacter pylori infection is the strongest known risk factor for the development of gastric cancer. The bacterium leverages several unique virulence factors to its advantage in order to colonize the human host. Among these, T4SS-delivered cytotoxin-associated gene A (CagA) has the most well-established links to severe forms of disease. To explore the effect of lactobacilli in disrupting CagA functions within host cells, we expressed HA-tagged humanized cagA in the human gastric epithelial AGS cell line and studied both the phosphorylation levels of CagA and its downstream binding partners. We found that gastric-specific Lactobacillus gasseri Kx110 A1 suppressed the phosphorylation of CagA and inhibited phosphorylation-dependent downstream signaling, resulting in the suppression of CagA-induced cell elongation of AGS cells, commonly known as the hummingbird phenotype. Surprisingly, phosphorylation-independent signaling was unaffected by L. gasseri. Furthermore, our confocal microscopy analysis revealed that CagA was mislocalized to the cytoplasm, suggesting that L. gasseri interferes with its membrane localization and thereby hinders its phosphorylation. Live L. gasseri that had direct contact with host cells was found to be necessary to suppress the hummingbird phenotype. In summary, the data suggest that a L. gasseri strain can inhibit CagA phosphorylation and suppress cell elongation. Full article

Fluorescent chemosensors are increasingly becoming relevant in recognition chemistry due to their sensitivity, selectivity, fast response time, real-time detection capability, and low cost. Boronic acids have been reported for the recognition of mycolactone, the cytotoxin responsible for tissue damage in Buruli ulcer disease. A library of fluorescent arylboronic acid chemosensors with various signaling moieties with certain beneficial photophysical characteristics (i.e., aminoacridine, aminoquinoline, azo, BODIPY, coumarin, fluorescein, and rhodamine variants) and a recognition moiety (i.e., boronic acid unit) were rationally designed and synthesised using combinatorial approaches, purified, and fully characterised using a set of complementary spectrometric and spectroscopic techniques such as NMR, LC-MS, FT-IR, and X-ray crystallography. In addition, a complete set of basic photophysical quantities such as absorption maxima (λ_abs^max), emission maxima (λ_em^max), Stokes shift (∆λ), molar extinction coefficient (ε), fluorescence quantum yield (Φ_F), and brightness were determined using UV-vis absorption and fluorescence emission spectroscopy techniques. The synthesised arylboronic acid chemosensors were investigated as chemosensors for mycolactone detection using the fluorescent-thin layer chromatography (f-TLC) method. Compound 7 (with a coumarin core) emerged the best (λ_abs^max = 456 nm, λ_em^max = 590 nm, ∆λ = 134 nm, ε = 52816 M⁻¹cm⁻¹, Φ_F = 0.78, and brightness = 41,197 M⁻¹cm⁻¹). Full article

Snakebite envenoming is a neglected tropical disease that causes substantial mortality and morbidity globally. The puff adder (Bitis arietans) and saw-scaled viper (Echis romani) have cytotoxic venoms that cause permanent injury via dermonecrosis around the bite site. Identifying the cytotoxic toxins within these venoms will allow for the development of targeted treatments to prevent snakebite morbidity. In this study, venoms from both species were fractionated using gel filtration chromatography, and a combination of cytotoxicity approaches, SDS-PAGE gel electrophoresis, and enzymatic assays were applied to identify the venom cytotoxins in the resulting fractions. Our results indicate that snake venom metalloproteinase (SVMP) toxins are responsible for causing cytotoxic effects across both venoms. The PI subclass of SVMPs is likely the main driver of cytotoxicity following envenoming by B. arietans, while the structurally distinct PIII subclass of SVMPs is mostly responsible for conveying this effect in E. romani venom. Identifying distinct SVMPs as cytotoxicity-causing toxins in these two African viper venoms will facilitate the future design and development of novel therapeutics targeting these medically important venoms, which in turn could help to mitigate the severe life- and limb-threatening consequences of tropical snakebites. Full article

Polyketides (PKs) are a widespread class of secondary metabolites with recognised pharmacological properties. These molecules are abundantly produced in the marine environment, especially by dinoflagellate-photosynthetic organisms able to produce several PKs, including neurotoxins, cytotoxins, and immunomodulating agents. The biosynthesis of these compounds is driven by a conserved enzymatic process involving polyketide synthase complexes. Different genera of dinoflagellates produce PKs. Among them, dinoflagellates of the genus Amphidinium are of particular interest due to its ability to produce the following two major families of PKs: amphidinolides and amphidinols. These compounds display remarkable biological activities, including anticancer, antimicrobial, and antifungal effects, making them attractive targets for pharmaceutical research and development. However, the natural yield of Amphidinium-derived polyketides (APKs) is generally low, limiting their potential for sustainable molecular farming. This challenge has prompted interest in developing biotechnological strategies to enhance their production. This review aims to define the current state of studies about APKs, starting from their initial discoveries to the recent understanding of their biosynthetic pathways. Additionally, it summarizes the structures of compounds discovered, highlights their biotechnological potential, and discusses novel trends in their production. Full article

The issue of stray cats and dogs is a global concern with considerable implications for animal welfare and public health. This review aims to provide an updated and comprehensive analysis of non-surgical contraceptive methods tested in studies controlled in vivo in feline and canine females. Immunocontraception via vaccination against gonadotropin-releasing hormone (GnRH), the luteinizing hormone receptor, zona pellucida proteins, and sperm, or use of viral-vectored delivery, is yet developing. Hormonal treatment (progestins, androgens, or GnRH) analogs act directly to block the reproductive axis. However, it produced essential side effects. Analogs of kisspeptin, non-steroid anti-inflammatory drugs such as firocoxib, and delivery of cytotoxins to the pituitary have shown non-conclusive results. Additional methods have also been tested, such as intraovarian injection of necrosing compounds or intravaginal and intrauterine devices. At present, neither of these methods offers permanent sterility that can replace surgical sterilization techniques. To our knowledge, none are currently authorized by the Food and Drug Administration (FDA) or the European Medicines Agency (EMA) for contraceptive methods or sterilization of cats or dogs. Therefore, it is necessary to continue the development of a compound that warrants the sterility of cats and dogs. Full article

The treatment of proctological conditions, including hemorrhoids, anal fissures, and perianal abscesses, is often complicated by bacterial infections, particularly those involving multidrug-resistant Escherichia coli. This study presents the synthesis, characterization, and biological evaluation of the newly designed synthetic peptide AMPEC4, inspired by cytotoxin 5 from Naja ashei snake venom. AMPEC4 demonstrated potent antimicrobial properties with MIC values of 100 and 200 µg/mL, effectively inhibiting biofilm formation (up to 84%) and eradicating the pre-formed biofilm by up to 35%. The antibacterial activity of AMPEC4 was further supported by a membrane permeabilization assay, demonstrating its capacity to disrupt bacterial membrane integrity in a dose-dependent manner. Furthermore, AMPEC4 significantly promoted fibroblast migration, a critical step in tissue regeneration, while exhibiting notable biocompatibility, as evidenced by the absence of hemolytic, cytotoxic, and genotoxic effects. By addressing both infection control and tissue regeneration, AMPEC4 represents a promising therapeutic strategy for managing chronic wounds, particularly in the challenging environment of the anorectal region. Its ability to target Escherichia coli reference and clinical strains while accelerating the wound-healing process underscores its potential for future clinical applications. Full article

Spontaneous cell detachment describes an effect in which eukaryotic cells first sediment onto a heated chip and then detach from it spontaneously and collectively after a sharply defined dwell time t_d. This behavior is triggered by the temperature gradient between the chip and the colder supernatant liquid. Notably, t_d allows distinguishing between different yeast strains and cancer-cell lines. At the same time, it also varies in the presence of nutrients and cytotoxins, suggesting an added value of this method for pharmacological studies. In the present work, we study the role of fluid convection on the detachment of yeast cells experimentally and by simulations using a sample compartment with a variable aspect ratio. Hereby, we found that the absolute chip temperature, the strength of the temperature gradient and the number of cells inside the sample compartment all affect the dwell time t_d. To demonstrate the concept, we show that the spontaneous-detachment method can measure the impact of an antibiotic and an antiseptic drug on yeast cultures and corroborate this with reference assays. Full article

Three-finger toxins (TFTs), including neurotoxins and cytotoxins, form one of the largest families of snake venom proteins and interact with various biological targets. Neurotoxins target proteinaceous receptors while cytotoxins interact mainly with the lipids of cell membranes and to a lesser extent with carbohydrates. However, no data about the interaction of TFTs with nucleic acids can be found. To detect this interaction, we applied spectrophotometry, ion-paired HPLC and electrophoretic mobility shift assay (EMSA). Using spectrophotometry, we found that TFTs from cobra venom increased the optical density of an RNA solution in a time-dependent manner indicating toxin interaction with RNA. A decrease in the net negative charge of the RNA molecule upon interaction with neurotoxin II from cobra venom was revealed by ion-pair HPLC. EMSA showed decreased electrophoretic mobility of both RNA and DNA upon addition of different TFTs including the non-conventional cobra toxin WTX and water-soluble recombinant human three-finger protein lynx1. We suggest that the interaction with nucleic acids may be a common property of TFTs, and some biological effects of TFTs, for example, cytotoxin-induced apoptosis in cancer cell lines, may be mediated by interaction with nucleic acids. Full article

Members of the benthic marine dinoflagellate genus Amphidinium produce a variety of bioactive compounds, exhibiting potent cytotoxicity in cell assays. Crude methanolic extracts from three genetically distinct cultured strains of A. eilatiense J.J. Lee were screened for cytotoxicity against three human breast and four lung cancer cell lines to evaluate potential applications in anticancer therapy. A standard tetrazolium cell viability assay demonstrated that the methanolic crude extract (100 µg mL⁻¹) from strain AeSQ181 reduced cell viability by 20–35% in five cancer cell lines. Further bioassay-guided fractionation of these crude extracts yielded non-polar fractions (FNP-5 and FNP-6) with particularly high cytotoxic activity against lung (H1563) and breast (MDA-MB-231) adenocarcinoma cell lines. Untargeted metabolomic analysis of cytotoxic fractions by liquid chromatography coupled with high-resolution mass spectrometry (LC-HRMS) revealed a much richer chemical diversity profile than previous toxigenicity studies on Amphidinium that exclusively focused on linear and cyclic polyethers and their macrolide analogs as putative cytotoxins. This untargeted metabolomic study showed substantial differences in chemical composition between the biologically active and non-active fractions. Preliminary biological and chemical characterization of these A. eilatiense fractions confirms that this species is a rich source of bioactive natural products with potential applications such as anticancer therapeutics. Full article

Clostridioides difficile (C. difficile), a gram-positive, spore-forming bacillus, has emerged as a leading cause of healthcare-associated infections, significantly contributing to infectious diarrhea and increasing healthcare costs. This descriptive, cross-sectional study was conducted among Saudi Arabian nursing staff from July to December 2023 to assess their knowledge and practices related to the diagnosis and management of C. difficile infection (CDI). Data were collected using a modified questionnaire. Overall, 358 nurses were surveyed, and 66% reported knowledge of C. difficile procedures. However, only 30.4% of the respondents correctly classified C. difficile as an anaerobic bacillus, while 42.2% were aware of the organism’s common occurrence in healthy adult volunteers. Additionally, 55.6% of respondents were aware of risk factors and 48.9% could name typical medicines that might cause illness. Only 24.0% acknowledged the cytotoxin test as the gold standard for detection, 26.8% identified hand washing with water and soap as an effective method to prevent the transmission of CDI, and 36.3% identified oral metronidazole as the first-line treatment for CDI. In summary, this study revealed a significant lack of awareness among nurses in Saudi Arabia regarding various aspects of CDI, emphasizing the need for improved education and training to address the knowledge gaps and quality of patient care. Full article