|
Toxinoses
Microbial toxins are toxins produced by micro-organisms, including bacteria, fungi, protozoa, dinoflagellates, and viruses. Many microbial toxins promote infection and disease by directly damaging host tissues and by disabling the immune system. Endotoxins most commonly refer to the lipopolysaccharide (LPS) or lipooligosaccharide (LOS) that are in the outer plasma membrane of Gram-negative bacteria. The botulinum toxin, which is primarily produced by ''Clostridium botulinum'' and less frequently by other '' Clostridium'' species, is the most toxic substance known in the world. However, microbial toxins also have important uses in medical science and research. Currently, new methods of detecting bacterial toxins are being developed to better isolate and understand these toxin. Potential applications of toxin research include combating microbial virulence, the development of novel anticancer drugs and other medicines, and the use of toxins as tools in neurobiology and cellular biolog ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bacterial Infection
Pathogenic bacteria are bacteria that can cause disease. This article focuses on the bacteria that are pathogenic to humans. Most species of bacteria are harmless and are often beneficial but others can cause infectious diseases. The number of these pathogenic species in humans is estimated to be fewer than a hundred. By contrast, several thousand species are part of the gut flora present in the digestive tract. The body is continually exposed to many species of bacteria, including beneficial commensals, which grow on the skin and mucous membranes, and saprophytes, which grow mainly in the soil and in decaying matter. The blood and tissue fluids contain nutrients sufficient to sustain the growth of many bacteria. The body has defence mechanisms that enable it to resist microbial invasion of its tissues and give it a natural immunity or innate resistance against many microorganisms. Pathogenic bacteria are specially adapted and endowed with mechanisms for overcoming the n ... [...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] |
Sepsis
Sepsis, formerly known as septicemia (septicaemia in British English) or blood poisoning, is a life-threatening condition that arises when the body's response to infection causes injury to its own tissues and organs. This initial stage is followed by suppression of the immune system. Common signs and symptoms include fever, tachycardia, increased heart rate, hyperventilation, increased breathing rate, and mental confusion, confusion. There may also be symptoms related to a specific infection, such as a cough with pneumonia, or dysuria, painful urination with a pyelonephritis, kidney infection. The very young, old, and people with a immunodeficiency, weakened immune system may have no symptoms of a specific infection, and the hypothermia, body temperature may be low or normal instead of having a fever. Severe sepsis causes organ dysfunction, poor organ function or blood flow. The presence of Hypotension, low blood pressure, high blood Lactic acid, lactate, or Oliguria, low urine o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clostridioides Difficile Infection
''Clostridioides difficile'' infection (CDI or C-diff), also known as ''Clostridium difficile'' infection, is a symptomatic infection due to the bacterial spores, spore-forming bacterium ''Clostridioides difficile''. Symptoms include watery diarrhea, fever, nausea, and abdominal pain. It makes up about 20% of cases of antibiotic-associated diarrhea. Antibiotics can contribute to detrimental changes in gut microbiota; specifically, they decrease short-chain fatty acid absorption which results in osmotic, or watery, diarrhea. Complications may include colitis#Infectious, pseudomembranous colitis, toxic megacolon, perforation of the colon, and sepsis. ''Clostridioides difficile'' infection is spread by bacterial spores found within feces. Surfaces may become contaminated with the spores with further spread occurring via the hands of healthcare workers. Risk factors for infection include antibiotic or proton pump inhibitor use, hospitalization, other health problems, and older a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glycosyltransferase
Glycosyltransferases (GTFs, Gtfs) are enzymes ( EC 2.4) that establish natural glycosidic linkages. They catalyze the transfer of saccharide moieties from an activated nucleotide sugar (also known as the "glycosyl donor") to a nucleophilic glycosyl acceptor molecule, the nucleophile of which can be oxygen- carbon-, nitrogen-, or sulfur-based. The result of glycosyl transfer can be a carbohydrate, glycoside, oligosaccharide, or a polysaccharide. Some glycosyltransferases catalyse transfer to inorganic phosphate or water. Glycosyl transfer can also occur to protein residues, usually to tyrosine, serine, or threonine to give O-linked glycoproteins, or to asparagine to give N-linked glycoproteins. Mannosyl groups may be transferred to tryptophan to generate C-mannosyl tryptophan, which is relatively abundant in eukaryotes. Transferases may also use lipids as an acceptor, forming glycolipids, and even use lipid-linked sugar phosphate donors, such as dolichol phosphates in eukaryotic o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clostridium Difficile Toxin B
Clostridium difficile toxin B is a cytotoxin produced by the bacteria ''Clostridioides difficile (bacteria), Clostridioides difficile'', formerly known as ''Clostridium difficile''. It is one of two major kinds of toxins produced by ''C. difficile'', the other being an related enterotoxin (Clostridium difficile toxin A, Toxin A). Both are very potent and lethal. Structure Toxin B (TcdB) is a cytotoxin that has a molecular weight of 270 kDa and an isoelectric point, pl, of 4.1. Toxin B has four different structural domains: catalytic, cysteine protease, protein translocation, translocation, and receptor binding. The N-terminal glucosyltransferase catalytic domain includes amino acid residues 1–544 while the cysteine protease domain includes residues 545–801. Additionally, the translocation region incorporates amino acid residues from 802 to 1664 while the receptor binding region is part of the C-terminal region and includes amino acid residues from 1665 to 2366. The gl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clostridium Difficile Toxin A
Clostridium difficile toxin A (TcdA) is a toxin generated by ''Clostridioides difficile'', formerly known as ''Clostridium difficile''. It is similar to ''Clostridium difficile'' Toxin B. The toxins are the main virulence factors produced by the gram positive, anaerobic, ''Clostridioides difficile'' bacteria. The toxins function by damaging the intestinal mucosa and cause the symptoms of ''C. difficile'' infection, including pseudomembranous colitis. TcdA is one of the largest bacterial toxins known. With a molecular mass of 308 kDa, it is usually described as a potent enterotoxin, but it also has some activity as a cytotoxin. The toxin acts by modifying host cell GTPase proteins by glucosylation, leading to changes in cellular activities. Risk factors for ''C. difficile'' infection include antibiotic treatment, which can disrupt normal intestinal microbiota and lead to colonization of ''C. difficile'' bacteria. ''tcdA'' gene The gene contains an open reading frame (ORF ... [...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] |
Hemolysin
Hemolysins or haemolysins are lipids and proteins that cause lysis of red blood cells by disrupting the cell membrane. Although the lytic activity of some microbe-derived hemolysins on red blood cells may be of great importance for nutrient acquisition, many hemolysins produced by pathogens do not cause significant destruction of red blood cells during infection. However, hemolysins are often capable of lysing red blood cells ''in vitro''. While most hemolysins are protein compounds, some are lipid biosurfactants. Properties Many bacteria produce hemolysins that can be detected in the laboratory. It is now believed that many clinically relevant fungi also produce hemolysins. Hemolysins can be identified by their ability to lyse red blood cells ''in vitro''. Not only are the erythrocytes affected by hemolysins, but there are also some effects among other blood cells, such as leucocytes (white blood cells). ''Escherichia coli'' hemolysin is potentially cytotoxic to monocytes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Leukocidin
A leukocidin is a type of cytotoxin created by some types of bacteria (''Staphylococcus''). It is a type of pore-forming toxin. The model for pore formation is step-wise. First, the cytotoxin’s “S” subunit recognizes specific protein-containing receptors, or an integrin on the host cell’s surface. The S subunit then recruits a second, “F” subunit, and the two subunits dimerize on the surface of the host’s cell. After dimerization, oligomerization occurs. Finally, the oligomers, consisting of alternating S and F subunits, undergo a significant structural change and form a beta-barrel, that pierces through the host cell’s lipid bilayer. Leukocidins get their names by killing ("-cide") leukocytes. Leukocidins target phagocytes, natural killer cells, dendritic cells, and T lymphocytes and therefore targets both, innate and adaptive immune responses. Leukocidins fall into the category of bacterial invasin Invasins are a class of proteins associated with the penetration ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neurotoxin
Neurotoxins are toxins that are destructive to nerve tissue (causing neurotoxicity). Neurotoxins are an extensive class of exogenous chemical neurological insultsSpencer 2000 that can adversely affect function in both developing and mature nervous tissue.Olney 2002 The term can also be used to classify endogenous compounds, which, when abnormally contacted, can prove neurologically toxic. Though neurotoxins are often neurologically destructive, their ability to specifically target neural components is important in the study of nervous systems. Common examples of neurotoxins include lead, ethanol (drinking alcohol), glutamate,Choi 1987 nitric oxide, botulinum toxin (e.g. Botox), tetanus toxin,Simpson 1986 and tetrodotoxin. Some substances such as nitric oxide and glutamate are in fact essential for proper function of the body and only exert neurotoxic effects at excessive concentrations. Neurotoxins inhibit neuron control over ion concentrations across the cell membrane, or com ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Enterotoxin
An enterotoxin is a protein exotoxin released by a microorganism that targets the intestines. Enterotoxins are chromosomally encoded or plasmid encoded exotoxins that are produced and secreted from several bacterial organisms. They are heat labile (>60⁰), and are of low molecular weight and water-soluble. Enterotoxins are frequently cytotoxic and kill cells by altering the apical membrane permeability of the mucosal (epithelial) cells of the intestinal wall. They are mostly pore-forming toxins (mostly chloride pores), secreted by bacteria, that assemble to form pores in cell membranes. This causes the cells to die. Clinical significance Enterotoxins have a particularly marked effect upon the gastrointestinal tract, causing traveler's diarrhea and food poisoning. The action of enterotoxins leads to increased chloride ion permeability of the apical membrane of intestinal mucosal cells. These membrane pores are activated either by increased cAMP or by increased calcium ion c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
