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Exotoxin
An exotoxin is a toxin secreted by bacteria. An exotoxin can cause damage to the host by destroying cells or disrupting normal cellular metabolism. They are highly potent and can cause major damage to the host. Exotoxins may be secreted, or, similar to endotoxins, may be released during lysis of the cell. Gram negative pathogens may secrete outer membrane vesicles containing lipopolysaccharide endotoxin and some virulence proteins in the bounding membrane along with some other toxins as intra-vesicular contents, thus adding a previously unforeseen dimension to the well-known eukaryote process of membrane vesicle trafficking, which is quite active at the host–pathogen interface. They may exert their effect locally or produce systemic effects. Well-known exotoxins include: botulinum toxin produced by ''Clostridium botulinum''; '' Corynebacterium diphtheriae'' toxin, produced during life-threatening symptoms of diphtheria; tetanospasmin produced by ''Clostridium tetani''. The toxi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Streptococcus Pyogenes
''Streptococcus pyogenes'' is a species of Gram-positive, aerotolerant bacteria in the genus ''Streptococcus''. These bacteria are extracellular, and made up of non-motile and non-sporing cocci (round cells) that tend to link in chains. They are clinically important for humans, as they are an infrequent, but usually pathogenic, part of the skin microbiota that can cause Group A streptococcal infection. ''S. pyogenes'' is the predominant species harboring the Lancefield group A antigen, and is often called group A ''Streptococcus'' (GAS). However, both '' Streptococcus dysgalactiae'' and the '' Streptococcus anginosus'' group can possess group A antigen as well. Group A streptococci, when grown on blood agar, typically produce small (2–3 mm) zones of beta-hemolysis, a complete destruction of red blood cells. The name group A (beta-hemolytic) ''Streptococcus'' (GABHS) is thus also used. The species name is derived from Greek words meaning 'a chain' () of berries ( a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Toxoid
A toxoid is an inactivated toxin (usually an exotoxin) whose toxicity has been suppressed either by chemical (formalin) or heat treatment, while other properties, typically immunogenicity, are maintained. Toxins are secreted by bacteria, whereas toxoids are altered form of toxins; toxoids are ''not'' secreted by bacteria. Thus, when used during vaccination, an immune response is mounted and immunological memory is formed against the molecular markers of the toxoid without resulting in toxin-induced illness. Such a preparation is also known as an anatoxin. There are toxoids for prevention of diphtheria, tetanus and botulism. Toxoids are used as vaccines because they induce an immune response to the original toxin or increase the response to another antigen since the toxoid markers and toxin markers are preserved. For example, the tetanus toxoid is derived from the tetanospasmin produced by ''Clostridium tetani''. The latter causes tetanus and is vaccinated against by the DTaP vac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. Bacteria inhabit soil, water, acidic hot springs, radioactive waste, and the deep biosphere of Earth's crust. Bacteria are vital in many stages of the nutrient cycle by recycling nutrients such as the fixation of nitrogen from the atmosphere. The nutrient cycle includes the decomposition of dead bodies; bacteria are responsible for the putrefaction stage in this process. In the biological communities surrounding hydrothermal vents and cold seeps, extremophile bacteria provide the nutrients needed to sustain life by converting dissolved compounds, such as hydrogen sulphide and methane, to energy. Bacteria also live in symbiotic and parasitic relationsh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Superantigens
Superantigens (SAgs) are a class of antigens that result in excessive activation of the immune system. Specifically it causes non-specific activation of T-cells resulting in polyclonal T cell activation and massive cytokine release. SAgs are produced by some pathogenic viruses and bacteria most likely as a defense mechanism against the immune system. Compared to a normal antigen-induced T-cell response where 0.0001-0.001% of the body's T-cells are activated, these SAgs are capable of activating up to 20% of the body's T-cells. Furthermore, Anti- CD3 and Anti-CD28 antibodies (CD28-SuperMAB) have also shown to be highly potent superantigens (and can activate up to 100% of T cells). The large number of activated T-cells generates a massive immune response which is not specific to any particular epitope on the SAg thus undermining one of the fundamental strengths of the adaptive immune system, that is, its ability to target antigens with high specificity. More importantly, the larg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Staphylococcus Aureus
''Staphylococcus aureus'' is a Gram-positive spherically shaped bacterium, a member of the Bacillota, and is a usual member of the microbiota of the body, frequently found in the upper respiratory tract and on the skin. It is often positive for catalase and nitrate reduction and is a facultative anaerobe that can grow without the need for oxygen. Although ''S. aureus'' usually acts as a commensal of the human microbiota, it can also become an opportunistic pathogen, being a common cause of skin infections including abscesses, respiratory infections such as sinusitis, and food poisoning. Pathogenic strains often promote infections by producing virulence factors such as potent protein toxins, and the expression of a cell-surface protein that binds and inactivates antibodies. ''S. aureus'' is one of the leading pathogens for deaths associated with antimicrobial resistance and the emergence of antibiotic-resistant strains, such as methicillin-resistant ''S. aureus'' (MRSA ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diphtheria
Diphtheria is an infection caused by the bacterium '' Corynebacterium diphtheriae''. Most infections are asymptomatic or have a mild clinical course, but in some outbreaks more than 10% of those diagnosed with the disease may die. Signs and symptoms may vary from mild to severe and usually start two to five days after exposure. Symptoms often come on fairly gradually, beginning with a sore throat and fever. In severe cases, a grey or white patch develops in the throat. This can block the airway and create a barking cough as in croup. The neck may swell in part due to enlarged lymph nodes. A form of diphtheria which involves the skin, eyes or genitals also exists. Complications may include myocarditis, inflammation of nerves, kidney problems, and bleeding problems due to low levels of platelets. Myocarditis may result in an abnormal heart rate and inflammation of the nerves may result in paralysis. Diphtheria is usually spread between people by direct contact or through th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polymorphic Toxins
Polymorphic toxins (PTs) are multi-domain proteins primarily involved in competition between bacteria but also involved in pathogenesis when injected in eukaryotic cells. They are found in all major bacterial clades. Bacteria live in complex multispecies communities such as biofilms and human-associated microbiotas. The dynamics and structure of these communities are greatly influenced by interbacterial competition through the secretion of toxic effectors. Bacteria have evolved several systems to outcompete their neighbors by poisoning them through a contact-dependent killing (including effectors of type V and VI secretion systems) or the release of soluble toxins (including colicins) in the environment. Definition Polymorphic toxins are bacterial exotoxins which share common features regarding their domain architecture. Each family of PTs is defined by a conserved N-terminal region associated with diverse C-terminal (CT) toxic domains, which can be found in several other PT fa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Endotoxin
Lipopolysaccharides (LPS) are large molecules consisting of a lipid and a polysaccharide that are bacterial toxins. They are composed of an O-antigen, an outer core, and an inner core all joined by a covalent bond, and are found in the outer membrane of Gram-negative bacteria. Today, the term ''endotoxin'' is often used synonymously with LPS, although there are a few endotoxins (in the original sense of toxins that are inside the bacterial cell that are released when the cell disintegrates) that are not related to LPS, such as the so-called delta endotoxin proteins produced by '' Bacillus thuringiensis''. Lipopolysaccharides can have substantial impacts on human health, primarily through interactions with the immune system. LPS is a potent activator of the immune system and pyrogen (agent that causes fever). In severe cases, LPS can play a role in causing septic shock. In lower levels and over a longer time period, there is evidence LPS may play an important and harmful role ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Toxin
A toxin is a naturally occurring organic poison produced by metabolic activities of living cells or organisms. Toxins occur especially as a protein or conjugated protein. The term toxin was first used by organic chemist Ludwig Brieger (1849–1919) and is derived from the word toxic. Toxins can be small molecules, peptides, or proteins that are capable of causing disease on contact with or absorption by body tissues interacting with biological macromolecules such as enzymes or cellular receptors. Toxins vary greatly in their toxicity, ranging from usually minor (such as a bee sting) to potentially fatal even at extremely low doses (such as botulinum toxin). Toxins are largely secondary metabolites, which are organic compounds that are not directly involved in an organism's growth, development, or reproduction, instead often aiding it in matters of defense. Terminology Toxins are often distinguished from other chemical agents strictly based on their biological origin. Le ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Toxic Shock Syndrome
Toxic shock syndrome (TSS) is a condition caused by bacterial toxins. Symptoms may include fever, rash, skin peeling, and low blood pressure. There may also be symptoms related to the specific underlying infection such as mastitis, osteomyelitis, necrotising fasciitis, or pneumonia. TSS is typically caused by bacteria of the ''Streptococcus pyogenes'' or ''Staphylococcus aureus'' type, though others may also be involved. Streptococcal toxic shock syndrome is sometimes referred to as toxic-shock-like syndrome (TSLS). The underlying mechanism involves the production of superantigens during an invasive streptococcus infection or a localized staphylococcus infection. Risk factors for the staphylococcal type include the use of very absorbent tampons, skin lesions in young children characterized by fever, low blood pressure, rash, vomiting and/or diarrhea, and multiorgan failure. Diagnosis is typically based on symptoms. Treatment includes intravenous fluids, antibiotics, incision ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Botulinum Toxin
Botulinum toxin, or botulinum neurotoxin (BoNT), is a neurotoxic protein produced by the bacterium ''Clostridium botulinum'' and related species. It prevents the release of the neurotransmitter acetylcholine from axon endings at the neuromuscular junction, thus causing flaccid paralysis. The toxin causes the disease botulism. The toxin is also used commercially for medical and cosmetic purposes. The seven main types of botulinum toxin are named types A to G (A, B, C1, C2, D, E, F and G). New types are occasionally found. Types A and B are capable of causing disease in humans, and are also used commercially and medically. Types C–G are less common; types E and F can cause disease in humans, while the other types cause disease in other animals. Botulinum toxins are among the most potent toxins known. Intoxication can occur naturally as a result of either wound or intestinal infection or by ingesting formed toxin in food. The estimated human lethal dose of type A toxin is 1.3 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clostridium Botulinum
''Clostridium botulinum'' is a Gram-positive, rod-shaped, anaerobic, spore-forming, motile bacterium with the ability to produce the neurotoxin botulinum. The botulinum toxin can cause botulism, a severe flaccid paralytic disease in humans and other animals, and is the most potent toxin known to mankind, natural or synthetic, with a lethal dose of 1.3–2.1 ng/kg in humans.(2010). Chapter 19. ''Clostridium'', ''Peptostreptococcus'', ''Bacteroides'', and Other Anaerobes. In Ryan K.J., Ray C (Eds), ''Sherris Medical Microbiology'', 5th ed. ''C. botulinum'' is a diverse group of pathogenic bacteria initially grouped together by their ability to produce botulinum toxin and now known as four distinct groups, ''C. botulinum'' groups I–IV, as well as some strains of ''Clostridium butyricum'' and ''Clostridium baratii'', are the bacteria responsible for producing botulinum toxin. ''C. botulinum'' is responsible for foodborne botulism (ingestion of preformed toxin), infant bot ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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