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Concept: Exotoxin


Excessive weight and obesity are associated with the development of diabetes mellitus type 2 (DMII) in humans. They also pose high risks of Staphylococcus aureus colonization and overt infections. S. aureus causes a wide range of severe illnesses in both healthy and immunocompromised individuals. Among S. aureus virulence factors, superantigens are essential for pathogenicity. In this study, we show that rabbits that are chronically exposed to S. aureus superantigen toxic shock syndrome toxin-1 (TSST-1) experience impaired glucose tolerance, systemic inflammation, and elevated endotoxin levels in the bloodstream, all of which are common findings in DMII. Additionally, such DMII-associated findings are also seen through effects of TSST-1 on isolated adipocytes. Collectively, our findings suggest that chronic exposure to S. aureus superantigens facilitates the development of DMII, which may lead to therapeutic targeting of S. aureus and its superantigens.

Concepts: Immune system, Nutrition, Diabetes mellitus, Staphylococcus aureus, Streptococcus pyogenes, Glucose tolerance test, Toxic shock syndrome, Exotoxin


The study aimed to report 2 cases of desquamative inflammatory vaginitis associated with toxic shock syndrome toxin 1 (TSST-1)-producing Staphylococcus aureus strains.

Concepts: Staphylococcus aureus, Streptococcus pyogenes, Syndromes, Clindamycin, Toxic shock syndrome, Exotoxin, Necrotizing fasciitis, Menstrual cup


Method of highly sensitive registration of magnetic nanoparticles by their non-linear magnetization is used in a novel sandwich-type immunoassay for detection of staphylococcal toxins in complex media of virtually any volume, with increasing sensitivity at higher sample volume. The signal is read out from the entire volume of a non-transparent 3D fiber structure employed as a solid phase, which provides large reaction surface, quick reagent mixing as well as antigen immunofiltration directly in the course of the assay. The method has demonstrated near-linear dose-response curves within wide range of ~3 decades while detection of staphylococcal enterotoxin A (SEA) and toxic shock syndrome toxin (TSST) in neat milk without sample preparation. The limits of detection (LOD) as low as 4 and 10 pg/mL for TSST and SEA, respectively, were obtained in 2-hour format using 30-mL samples. The second, 25-minute format, showed the LOD of 0.1 and 0.3 ng/mL for the same toxins in a 150 µL sample. The developed immunoassay can be applied in food safety control, in vitro diagnostics and veterinary for a variety of research from express tests in the field to highly sensitive laboratory tests.

Concepts: Magnetic field, Staphylococcus aureus, Streptococcus pyogenes, ELISA, Toxic shock syndrome, Exotoxin, Necrotizing fasciitis, Magnetic immunoassay


Protein toxins, such as botulinum neurotoxins (BoNTs), Clostridium perfringens epsilon toxin (ETX), staphylococcal enterotoxin B (SEB), shiga toxin (STX), and plant toxin ricin, are involved in a number of diseases and are considered as potential agents for bioterrorism and warfare. From a bioterrorism and warfare perspective, these agents are likely to cause maximum damage to a civilian or military population through an inhalational route of exposure and aerosol is considered the envisaged mode of delivery. Unambiguous detection of toxin from aerosol is of paramount importance, both for bringing mitigation protocols into operation and for implementation of effective medical countermeasures, in case a “biological cloud” is seen over a population. A multiplex, unambiguous, and qualitative detection of protein toxins is reported here using tandem mass spectrometry with MALDI-TOF-TOF. The methodology involving simple sample processing steps was demonstrated to identify toxins (ETX, Clostridium perfringes phospholipase C, and SEB) from blind spiked samples. The novel directed search approach using a list of unique peptides was used to identify toxins from a complex protein mixture. The bioinformatic analysis of seven protein toxins for elucidation of unique peptides with conservation status across all known sequences provides a high confidence for detecting toxins originating from any geographical location and source organism. Use of tandem MS data with peptide sequence information increases the specificity of the method. A prototype for generation of aerosol using a nebulizer and collection using a cyclone collector was used to provide a proof of concept for unambiguous detection of toxin from aerosol using precursor directed tandem mass spectrometry combined with protein database searching. ETX prototoxin could be detected from aerosol at 0.2 ppb concentration in aerosol.

Concepts: Protein, Mass spectrometry, Peptide, Exotoxin, Toxin, Tandem mass spectrometry, Clostridium perfringens, Microbial toxins


Many pathogens secrete toxins that target key host processes resulting in the activation of immune pathways. The secreted Pseudomonas aeruginosa toxin Exotoxin A (ToxA) disrupts intestinal protein synthesis, which triggers the induction of a subset of P. aeruginosa-response genes in the nematode Caenorhabditis elegans.

Concepts: DNA, Protein, Cell, Bacteria, Virus, RNA, Caenorhabditis elegans, Exotoxin


The bacterium Staphylococcus aureus is an important cause of the life-threatening condition toxic shock syndrome in humans. Bacterial toxins known as superantigens (SAgs) generate this illness by acting as broad activators of a substantial fraction of all T lymphocytes, bypassing the normally highly stringent T-cell receptor antigen specificity to cause a systemic inflammatory cytokine storm in the host. In a new study, Shaler et al. found that immune cells called mucosa-associated invariant T (MAIT) cells make an unexpectedly large contribution to the SAg response in a largely T-cell receptor-independent, cytokine-driven manner. Subsequent to such activation, the MAIT cells remain unresponsive to stimulation with bacterial antigen. Thus, S. aureus hijacks MAIT cells in the cytokine storm and leaves them functionally impaired. This work provides new insight into the role of MAIT cells in antibacterial immunity and opens new avenues of investigation to understand and possibly treat bacterial toxic shock and sepsis.

Concepts: Immune system, Antibody, Bacteria, Staphylococcus aureus, T cell receptor, Toxic shock syndrome, Exotoxin, Superantigen


Bicomponent pore-forming leukocidins are a family of potent toxins secreted by Staphylococcus aureus, which target white blood cells preferentially and consist of an S- and an F-component. The S-component recognizes a receptor on the host cell, enabling high-affinity binding to the cell surface, after which the toxins form a pore that penetrates the cell lipid bilayer. Until now, six different leukocidins have been described, some of which are host and cell specific. Here, we identify and characterise a novel S. aureus leukocidin; LukPQ. LukPQ is encoded on a 45 kb prophage (ΦSaeq1) found in six different clonal lineages, almost exclusively in strains cultured from equids. We show that LukPQ is a potent and specific killer of equine neutrophils and identify equine-CXCRA and CXCR2 as its target receptors. Although the S-component (LukP) is highly similar to the S-component of LukED, the species specificity of LukPQ and LukED differs. By forming non-canonical toxin pairs, we identify that the F-component contributes to the observed host tropism of LukPQ, thereby challenging the current paradigm that leukocidin specificity is driven solely by the S-component.

Concepts: White blood cell, Protein, Bacteria, Microbiology, Staphylococcus aureus, Cell biology, Staphylococcus, Exotoxin


Staphylococcus aureus is one of the most common causes of seafood-borne diseases worldwide, which are attributable to the contamination of food by preformed enterotoxins. In this study, a total of 206 (34.3%) Staphylococcus aureus strains were obtained from 600 fish and shrimp samples and were tested for their antimicrobial susceptibility. We assessed the prevalence of the genes responsible for the staphylococcal enterotoxins (SEA, SEB) and toxic shock syndrome toxin 1 (TSST-1) genes. The results indicated that 34% of aqua food samples were contaminated with S. aureus, and 23.8% of these isolates were mec-A-positive. Sixty-four percent of the strains isolated from contaminated seafood was enterotoxigenic S. aureus, and 28.2% of SEs were MRSA-positive. The most prevalent genotype was characterized by the presence of the sea gene (45.2%), followed by the seb gene (18.5%), and the tst gene encoding TSST-1 was found in eight strains (3.9%). Of the 206 S. aureus isolates, 189 strains (84.9%) were resistant to at least one antibiotic. Given the frequent outbreaks of enterotoxigenic MRSA, it is necessary to make revisions to mandatory programmes to facilitate improved hygiene practices during fishing, aquaculture, processing, and sales to prevent the contamination of fishery products in Iran.

Concepts: Bacteria, Staphylococcus aureus, Antibiotic resistance, Staphylococcus, Methicillin-resistant Staphylococcus aureus, Clindamycin, Toxic shock syndrome, Exotoxin


In the present study, a colorimetric DNAzymes biosensor strategy was devised in combination with immunomagnetic separation for rapid and easy detection of enterotoxin B harbouring Staphylococcus aureus from food and clinical samples. The method employs immunocapture of S. aureus and amplification of seb gene by DNAzyme complementary sequence integrated forward primer and with specific reverse primer. The DNAzyme sequence integrated dsDNA PCR products when treated with hemin and TMB (3, 3', 5, 5'-tetramethylbenzidine) in the presence of H2O2 produce colorimetric signal. A linear relationship of optical signal with the initial template of seb was obtained which could be monitored by visually or spectrophotometrically for qualitative and quantitative detection. The limit of detection for the assay was approximately 102 CFU/mL of seb gene harboring target. This method is convenient compared to gel based and ELISA systems. Further, spiking studies and analysis on natural samples emphasized the robustness and applicability of developed method. Altogether, the established assay could be a reliable alternative, low-cost, viable detection tool for the routine investigation of seb from food and clinical sources.

Concepts: Polymerase chain reaction, Staphylococcus aureus, Antibiotic resistance, Staphylococcus, Qualitative research, Exotoxin, Coagulase, Enterotoxin


Number of previous reviews had described the structures and the various functions of the exotoxins produced by the type-3 secretion system of Pseudomonas aeruginosa and their roles in the interactions of this bacterium with host cells. In this review, we summarize some relevant data of literature on ExoS, an exotoxin from the type-3 secretion system of P. aeruginosa, with a particular focus on the role of this toxin in the airways innate response of the host to infection by this bacterium, and its implication in the elimination of Staphylococcus aureus from the airways of patients with cystic fibrosis.

Concepts: Immune system, Bacteria, Pneumonia, Staphylococcus aureus, Antibiotic resistance, Pseudomonas aeruginosa, Cystic fibrosis, Exotoxin