Enterotoxicity

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As enterotoxicity ( gr. Toxins = toxic and enteron = intestine) is called a direct poison-like effects of different substances (sg enterotoxins ) to the intestinal tract , which leads to an increased excretion of liquid from the intestinal wall. This can be caused by microorganisms in the intestine (e.g. E. coli ) that form enterotoxins, or the direct ( oral ) ingestion of substances with a corresponding effect on the intestine (e.g. food poisoning ). The classic leading symptom of enterotoxicity is diarrhea .

Mechanism and definition of terms

The enterotoxicity leads to an increased secretion of fluid from certain intestinal mucous membrane cells ( enterocytes ) into the intestinal lumen. The extent of this reaction depends not only on the amount and type of toxin, but also on the (lipid) composition of your cell membrane . The resulting increased excretion of fluid in the stool can be life-threatening ( dehydration ).

Not all mechanisms through which bacterial infections lead to diseases of the gastrointestinal tract are referred to with the term enterotoxicity. These include the adherence of bacteria to the surface of the mucous membrane ( bacterial adherence ), the destruction of cells ( cytotoxicity ) and the penetration of the surface of the intestinal wall ( invasiveness ).

causes

Substances that are in the intestinal lumen or are formed there by microorganisms are responsible for the toxic effects. A distinction is made between endotoxins and exotoxins . However, the term is also used for the effects of other substances (e.g. methotrexate ) on the intestinal surface.

Endo- and exotoxins

In endotoxins is components of cell membranes of ( gram-negative ) bacteria that are released in the intestinal lumen when the bacteria die or actively eliminate them. From a biochemical point of view, these are typically lipopolysaccharides whose lipid components are held responsible for the toxic effects and whose saccharide components are responsible for the immunogenically mediated effects. Examples of enterotoxicity triggered in this way are infections with Escherichia coli , salmonella ( salmonellosis ), shigella ( bacterial dysentery ) and pseudomonads .

The exotoxins is toxins that are actively secreted by bacteria. From a biochemical point of view, these are typically proteins ( polypeptides or proteins ). For example, dissolves Vibrio cholerae by the precipitation of cholera toxin , the cholera , a life-threatening diarrhea from.

Place where the poison arises

Enterotoxicity can be triggered by substances that are already in the food before consumption ( food poisoning ). Typical causes are Staphylococcus aureus , more rarely Clostridium perfringens and Bacillus cereus .

Alternatively, these toxins can also arise in relevant quantities after colonization of the intestinal tract and corresponding reproduction of the bacteria (e.g. Vibrio cholerae and Salmonella ).

Clinical pictures

Enterotoxicity leads to an increased fluid content of the faeces and is thus the cause of various clinical pictures. Clinically, these are usually diarrhea and often vomiting. Conversely, however, not every diarrheal illness is caused by enterotoxicity; other causes can also be present (e.g. EHEC infection). Mixed forms, in the development of which different factors are involved, also occur (e.g. food poisoning by Bacillus cereus - see below ).

The loss of fluid associated with enterotoxic clinical pictures can lead in the medium term to "drying out" (dehydration) of the body and thus ultimately to death via the stage of hypovolemic shock . Children are even more at risk than adults from the associated loss of water.

Food poisoning

In cases of food intoxication, the enterotoxins are already in critical quantities in the food before consumption. Neither the multiplication of the pathogens nor their toxin production after ingestion in the gastrointestinal tract play a significant role.

Staphylococcal enteritis

The vast majority (90%) of the by Staphylococcus aureus triggered Staphylokokkenenteritiden is to be distinguished immunologically by enterotoxin A, of the current 7 different variants, triggered. A mechanism of action has not yet been definitively proven, 2 possible approaches are being discussed. On the one hand, these enterotoxins could act as so-called " superantigens " (release of interleukin 2 from T cells and tumor necrosis factor -α from macrophages ) and, on the other hand, they could directly damage the nerve endings of the vagus nerve . Less than 1μg of toxin is required to trigger symptoms.

Clostridium perfringens enteritis

Enterotoxicity exists in Clostridium perfringens type A. A component of its spore envelope is a polypeptide , which corresponds to a receptor on the enterocyte cell membrane . If the toxin binds to this receptor, protein synthesis and the cytoskeleton of the affected cell are disrupted, which leads to a reduction in active non-electrolyte resorption .

Diarrhea caused by Bacillus cereus

The non-hemolytic enterotoxin (NHE) and the hemolysin BL (HBL) act as enterotoxins in diarrheal disease caused by Bacillus cereus . A third enterotoxin has been described for the bacterium, the necrotizing cytotoxin K, the main effect of which is cytotoxic .

Infectious diarrheal diseases

The pathogens that cause the disease are particularly often transmitted via faecal-oral infection routes or via food. A certain amount gets into the intestinal tract (after overcoming the acid barrier of the stomach ). When a critical number of pathogens (the number depends on their virulence ) has arrived there, they multiply and, depending on the type, form exo- or endotoxins, which trigger the corresponding symptoms.

Aeromonas

Aeromonas caviae, A. sobria and A. hydrophila are considered to be facultative human pathogens . The formation of an enterotoxin has been demonstrated for the latter, but its exact mechanism of action is not known.

Escherichia coli

The group of Escherichia coli leading to diseases of the gastrointestinal tract includes enterotoxic (ETEC), enteropathogenic (EPEC), enterohaemorrhagic (EHEC) and enteroinvasive (EIEC) forms. In the first, enterotoxicity is the cause of the clinical symptoms, which are often referred to as traveller's diarrhea . This requires at least 100 million pathogens.

Other diseases

Individual evidence

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  2. ↑ a b M. S. Hand: Clinical dietetics for small animals. Volume 1, Verlag Schlütersche, 2003, ISBN 3-87706-893-6 , p. 1390, books.google.de
  3. ↑ Focus: gastroenterology. (PDF) University of Veterinary Medicine Hannover, 2003, p. 14, accessed November 27, 2009.
  4. ↑ B. Ruehe: Basics gastroenterology. Urban & Fischer-Verlag, 2005, ISBN 3-437-42146-8 , p. 142, books.google.de
  5. ↑ T. Kenneth: Bacterial Endotoxin. In: Online Textbook of Bacteriology, 2008; Retrieved November 27, 2009.
  6. ↑ a b J. Stein: Practical Guide to Clinical Nutrition and Infusion Therapy. Springer, 2003, ISBN 3-540-41925-X , p. 815, books.google.de
  7. ^ BBB - Staphylococcus aureus. FDA, 2009; Retrieved November 27, 2009.
  8. ↑ Monika Ehling-Schulz : Toxin gene profiling of enterotoxic and emetic Bacillus cereus. In: FEMS Microbiol Lett. 2006 Jul; 260 (2), pp. 232-240, PMID 16842349
  9. ↑ Research report ( Memento of the original from May 11, 2005 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF) of the Weihenstephan Science Center, the Technical University of Munich - Institute for Microbiology Weihenstephan, 2002, p. 119; Retrieved November 27, 2009.  @1@ 2Template: Webachiv / IABot / www.wzw.tum.de
  10. ^ BBB - Aeromonas hydrophila. FDA, 2009; Retrieved November 27, 2009.
  11. ↑ BBB - Enterotoxigenic Escherichia coli (ETEC). FDA, 2009; Retrieved November 27, 2009