SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Toxic shock syndrome

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The group A Streptococcus (GAS) M1T1 clone emerged in the 1980s as a leading cause of epidemic invasive infections worldwide, including necrotizing fasciitis and toxic shock syndrome. Horizontal transfer of mobile genetic elements has played a central role in the evolution of the M1T1 clone, with bacteriophage-encoded determinants DNase Sda1 and superantigen SpeA2 contributing to enhanced virulence and colonization respectively. Outbreaks of scarlet fever in Hong Kong and China in 2011, caused primarily by emm12 GAS, led to our investigation of the next most common cause of scarlet fever, emm1 GAS. Genomic analysis of 18 emm1 isolates from Hong Kong and 16 emm1 isolates from mainland China revealed the presence of mobile genetic elements associated with the expansion of emm12 scarlet fever clones in the M1T1 genomic background. These mobile genetic elements confer expression of superantigens SSA and SpeC, and resistance to tetracycline, erythromycin and clindamycin. Horizontal transfer of mobile DNA conferring multi-drug resistance and expression of a new superantigen repertoire in the M1T1 clone should trigger heightened public health awareness for the global dissemination of these genetic elements.

Concepts: Genetics, Evolution, Staphylococcus aureus, Streptococcus pyogenes, Toxic shock syndrome, Necrotizing fasciitis, Mainland China, Scarlet fever

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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

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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

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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

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Staphylococcus aureus, a Gram-positive bacterium, can cause a range of illnesses from minor skin infections to life-threatening diseases, such as bacteraemia, endocarditis, meningitis, osteomyelitis, pneumonia, toxic shock syndrome and sepsis. Due to the emergence of antibiotic resistance strains, there is a need to develop of new class of antibiotics or drug for this pathogen. The phosphotransacetylase enzyme plays an important role in the acetate metabolism and found to be essential for the survival of the S. aureus. This enzyme was evaluated as a putative drug target for S. aureus by in silico analysis. The 3D structure of the phosphotransacetylase from S. aureus was modelled, using the 1TD9 chain ‘A’ from Bacillus subtilis as a template at the resolution of 2.75 Å. The generated model has been validated by PROCHECK, WHAT IF and SuperPose. The docking was performed by the Molegro virtual docker using the ZINC database generated ligand library. The ligand library was generated within the limitation of the Lipinski rule of five. Based on the dock-score, five molecules have been subjected to ADME/TOX analysis and subjected for pharmacophore model generation. The zinc IDs of the potential inhibitors are ZINC08442078, ZINC8442200, ZINC 8442087 and ZINC 8442184 and found to be pharmacologically active antagonist of phosphotransacetylase. The molecules were evaluated as no-carcinogenic and persistent molecule by START programme.

Concepts: Bacteria, Microbiology, Pneumonia, Staphylococcus aureus, Antibiotic resistance, Clindamycin, Toxic shock syndrome, Gram positive bacteria

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Superantigens (SAgs) are potent exotoxins secreted by Staphylococcus aureus and Streptococcus pyogenes. They target a large fraction of T cell pools to set in motion a “cytokine storm” with severe and sometimes life-threatening consequences typically encountered in toxic shock syndrome (TSS). Given the rapidity with which TSS develops, designing timely and truly targeted therapies for this syndrome requires identification of key mediators of the cytokine storm’s initial wave. Equally important, early host responses to SAgs can be accompanied or followed by a state of immunosuppression, which in turn jeopardizes the host’s ability to combat and clear infections. Unlike in mouse models, the mechanisms underlying SAg-associated immunosuppression in humans are ill-defined. In this work, we have identified a population of innate-like T cells, called mucosa-associated invariant T (MAIT) cells, as the most powerful source of pro-inflammatory cytokines after exposure to SAgs. We have utilized primary human peripheral blood and hepatic mononuclear cells, mouse MAIT hybridoma lines, HLA-DR4-transgenic mice, MAIThighHLA-DR4+ bone marrow chimeras, and humanized NOD-scid IL-2Rγnull mice to demonstrate for the first time that: i) mouse and human MAIT cells are hyperresponsive to SAgs, typified by staphylococcal enterotoxin B (SEB); ii) the human MAIT cell response to SEB is rapid and far greater in magnitude than that launched by unfractionated conventional T, invariant natural killer T (iNKT) or γδ T cells, and is characterized by production of interferon (IFN)-γ, tumor necrosis factor (TNF)-α and interleukin (IL)-2, but not IL-17A; iii) high-affinity MHC class II interaction with SAgs, but not MHC-related protein 1 (MR1) participation, is required for MAIT cell activation; iv) MAIT cell responses to SEB can occur in a T cell receptor (TCR) Vβ-specific manner but are largely contributed by IL-12 and IL-18; v) as MAIT cells are primed by SAgs, they also begin to develop a molecular signature consistent with exhaustion and failure to participate in antimicrobial defense. Accordingly, they upregulate lymphocyte-activation gene 3 (LAG-3), T cell immunoglobulin and mucin-3 (TIM-3), and/or programmed cell death-1 (PD-1), and acquire an anergic phenotype that interferes with their cognate function against Klebsiella pneumoniae and Escherichia coli; vi) MAIT cell hyperactivation and anergy co-utilize a signaling pathway that is governed by p38 and MEK1/2. Collectively, our findings demonstrate a pathogenic, rather than protective, role for MAIT cells during infection. Furthermore, we propose a novel mechanism of SAg-associated immunosuppression in humans. MAIT cells may therefore provide an attractive therapeutic target for the management of both early and late phases of severe SAg-mediated illnesses.

Concepts: Immune system, Protein, Cytokine, Staphylococcus aureus, Streptococcus pyogenes, Major histocompatibility complex, T cell receptor, Toxic shock syndrome

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ABSTRACT Infective endocarditis and kidney infections are serious complications of Staphylococcus aureus sepsis. We investigated the role of superantigens (SAgs) in the development of lethal sepsis, infective endocarditis, and kidney infections. SAgs cause toxic shock syndrome, but it is unclear if SAgs contribute to infective endocarditis and kidney infections secondary to sepsis. We show in the methicillin-resistant S. aureus strain MW2 that lethal sepsis, infective endocarditis, and kidney infections in rabbits are critically dependent on high-level SAgs. In contrast, the isogenic strain lacking staphylococcal enterotoxin C (SEC), the major SAg in this strain, is attenuated in virulence, while complementation restores disease production. SAgs' role in infective endocarditis appears to be both superantigenicity and direct endothelial cell stimulation. Maintenance of elevated blood pressure by fluid therapy significantly protects from infective endocarditis, possibly through preventing bacterial accumulation on valves and increased SAg elimination. These data should facilitate better methods to manage these serious illnesses. IMPORTANCE The Centers for Disease Control and Prevention reported in 2007 that Staphylococcus aureus is the most significant cause of serious infectious diseases in the United States (R. M. Klevens, M. A. Morrison, J. Nadle, S. Petit, K. Gershman, et al., JAMA 298:1763-1771, 2007). Among these infections are sepsis, infective endocarditis, and acute kidney injury. Infective endocarditis occurs in 30 to 60% of patients with S. aureus bacteremia and carries a mortality rate of 40 to 50%. Over the past decades, infective endocarditis outcomes have not improved, and infection rates are steadily increasing (D. H. Bor, S. Woolhandler, R. Nardin, J. Brusch, D. U. Himmelstein, PLoS One 8:e60033, 2013). There is little understanding of the S. aureus virulence factors that are key for infective endocarditis development and kidney abscess formation. We demonstrate that superantigens are critical in the causation of all three infections. We show that their association results from both superantigenicity and direct toxic effects on endothelial cells, the latter likely contributing to delayed endothelium healing. Our studies contribute significantly to understanding the development of these illnesses and are expected to lead to development of important therapies to treat such illnesses.

Concepts: Inflammation, Infectious disease, Atherosclerosis, Staphylococcus aureus, Infection, Endothelium, Toxic shock syndrome, Infective endocarditis

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Fifteen currently marketed intravaginal protection products (11 types of tampon and four menstrual cups) were tested by the modified tampon sac method to determine their effect on Staphylococcus aureus growth and toxic shock toxin 1 (TSST-1) production. Most tampons reduced S. aureus growth and TSST-1 production, with differences based on brand and composition, and S. aureus growth was higher in de-structured than in unaltered tampons. We observed higher S. aureus growth and toxin production in menstrual cups than in tampons, potentially due to the additional air introduced to the bag by cups, with differences based on cup composition and size.Importance Menstrual toxic shock syndrome is a rare but severe disease. It occurs in healthy women vaginally colonized by Staphylococcus aureus producing toxic shock syndrome toxin 1 using intravaginal protection such as tampons or menstrual cups. Intravaginal protection induces TSS production by collecting catamenial products which act as a growth medium for S. aureus Previous studies have evaluated the impact of tampon composition on S. aureus producing toxic shock syndrome toxin 1, but they are not recent and did not include menstrual cups. This study demonstrates that highly reproducible results for S. aureus growth and TSST-1 production can be obtained using a simple protocol that reproduces the physiological conditions of tampon and cup usage as closely as possible, providing recommendations for tampon or cup use to both manufacturers and consumers. Notably, our results do not show that menstrual cups are safer than tampons and suggest that they require similar precautions.

Concepts: Staphylococcus aureus, Staphylococcus, Clindamycin, Toxic shock syndrome, Exotoxin, Menstruation, Menstrual cup

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Bacterial superantigens (SAgs) cause Vβ-dependent T-cell proliferation leading to immune dysregulation associated with the pathogenesis of life-threatening infections such as toxic shock syndrome, and necrotizing pneumonia. Previously, we demonstrated that staphylococcal enterotoxin-like toxin X (SElX) from Staphylococcus aureus is a classical superantigen that exhibits T-cell activation in a Vβ-specific manner, and contributes to the pathogenesis of necrotizing pneumonia. Here, we discovered that SElX can also bind to neutrophils from human and other mammalian species and disrupt IgG-mediated phagocytosis. Site-directed mutagenesis of the conserved sialic acid-binding motif of SElX abolished neutrophil binding and phagocytic killing, and revealed multiple glycosylated neutrophil receptors for SElX binding. Furthermore, the neutrophil binding-deficient mutant of SElX retained its capacity for T-cell activation demonstrating that SElX exhibits mechanistically independent activities on distinct cell populations associated with acquired and innate immunity, respectively. Finally, we demonstrated that the neutrophil-binding activity rather than superantigenicity is responsible for the SElX-dependent virulence observed in a necrotizing pneumonia rabbit model of infection. Taken together, we report the first example of a SAg, that can manipulate both the innate and adaptive arms of the human immune system during S. aureus pathogenesis.

Concepts: Immune system, Antibody, Bacteria, Staphylococcus aureus, Innate immune system, Infection, Immunity, Toxic shock syndrome

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Staphylococcal toxic shock syndrome (TSS) was originally described in menstruating women and linked to TSS toxin 1 (TSST-1)-producing Staphylococcus aureus. Using UK national surveillance data, we ascertained clinical, molecular and superantigenic characteristics of TSS cases. Average annual TSS incidence was 0.07/100,000 population. Patients with nonmenstrual TSS were younger than those with menstrual TSS but had the same mortality rate. Children <16 years of age accounted for 39% of TSS cases, most caused by burns and skin and soft tissue infections. Nonmenstrual TSS is now more common than menstrual TSS in the UK, although both types are strongly associated with the tst+ clonal complex (CC) 30 methicillin-sensitive S. aureus lineage, which accounted for 49.4% of all TSS and produced more TSST-1 and superantigen bioactivity than did tst+ CC30 methicillin-resistant S. aureus strains. Better understanding of this MSSA lineage and infections in children could focus interventions to prevent TSS in the future.

Concepts: Epidemiology, Staphylococcus aureus, Staphylococcus, United Kingdom, Clindamycin, Toxic shock syndrome, Exotoxin, Coagulase