Toxins and Human Diseases - Assignment Example

THE TYPE OF TOXIN DETERMINES THE CHARACTERISTICS OF THE DISEASE 8/22 "THE TYPE OF TOXIN DETERMINES THE CHARACTERISTICS OF THE DISEASE" Human disease and pathologies can result from a large number of infectious agents. Different diseases result from the invasion of the body by different microorganisms. But another important feature also needs to be understood that not only differing infectious organisms can result in different diseases but also the kind of toxins produced by a single microorganism provide for a reason for the determination of the characteristics of the disease. This is because these toxins produced by the same microorganism invade different body tissues and invoke different bodily responses. Not only this, different toxins also possess differing severities of their action and hence it is the type of the toxin that predetermines the features of the resulting disease. Microorganisms like the staphylococcus aureus which is a gram positive bacterium, Escherichia coli and pseudomonas aeruginosa which are gram negative bacteria and other microorganisms provide as examples of bacteria which produce different toxins. These toxins in turn then lead to distinctive diseases which present with varying clinical signs and symptoms. These toxins may either be exotoxins and endotoxins. Staphylococcus aureus belongs to the class of gram negative cocci. This bacterium is associated with a large number of diseases. The production of toxins by the bacteria is one major way of leading to the pathologies associated with it. The major toxins produced by staphylococcus aureus include enterotoxin, toxic shock syndrome toxin, exfoliatin and leukocidins. The enterotoxin produced by the bacteria acts in the gastrointestinal tract and stimulates the macrophages and the helper T cells. These lead to the excessive production of interleukin 1 and interleukin 2. It also leads to the production of cytokines from the lymphoid cells. These stimulate the centre of the brain which is associated with vomiting. This toxin is hence clinically responsible for leading to food poisoning with profuse vomiting as well as diarrhoea. The other exotoxin produced by staphylococcus aureus is toxic shock syndrome toxin which affects not only the gastrointestinal tract but it may also affect the hepatic and the renal system as well as the brain and the vascular system. The patient may develop pyrexia, low blood pressure, rashes as well as disturbances of the gastrointestinal tract which include diarrhoea as well as vomiting. This toxin can lead to toxic shock by leading to the production of increased amount of interleukin 1, interleukin2 as well as the tumour necrosis factor. This toxin is mainly produced in the nasal cavity or the vagina due to infection in tampons or nasal packing. It then enters the bloodstream and produces the clinical effects. Exfoliatin is another exotoxin produced by the same bacteria which leads to a condition referred to as the “scalded skin syndrome. This condition affects the skin leading to rashes and also to pyrexia. Loss of nails as well as hair might also be seen. Alpha toxin and P-V leukocidin belong to the class of a toxin produced by staphylococcus aureus which is known as leukocidin. Alpha toxin affects the skin by leading to necrosis and it also leads to the breakdown of the red blood cells. P-V leukocidin causes the breakdown of the white blood cells in the body. It can also lead to infecting the skin as well as the soft tissues of the body. Pneumonia associated with necrosis is also led to by this toxin. It can be considered that different toxins produced by the same bacteria staphylococcus aureus, present with differing clinical manifestations. These toxins do not affect the same body systems but rather lead to pathologies of varying degrees and are not restricted to any one body system. They also present with signs and symptoms which are unique to each of them as for instance enterotoxin does affect the gastrointestinal tract but does not present with pyrexia and the toxic shock syndrome toxin leads to gastrointestinal disturbances as well as fever. Escherichia Coli is another class of bacteria which is mainly classified as a gram negative rod which affects the intestinal system but is also affects the other systems of the body. The bacteria has the capability of producing exotoxins which attack the enteric system. It also produces endotoxins which affect the other systems of the body. The bacteria has the capability of attaching to the walls of the small intestine and then leading to the production of toxins of the enteric system which include the heat labile toxin and the heat stable toxin. These toxins possess the capability of attaching to the G protein on the cells of the small intestine particularly the ileum and the jejunum. The heat labile toxin activates the adenylyl cyclise and the heat stable protein activates the guanylate cyclise. Hence they initiate a cascade of reactions which induce the activity of intracellular enzymes. These enzymes then activate the ion transporting machinery of the cell which performs its functions of moving essential ions which are normally retained within the cell into the lumen of the small intestine. These ions include potassium and chloride. The loss of these ions from the intestinal cells into the intestine leads to diarrhoea. These two toxins do not inflame or infect the cells of the small intestine and the diarrhoea is without blood. On the other hand verotoxin is a toxin produced by a strain of Escherichia coli which invades as well as leads to the inflammation of the walls of the large intestine. The resulting clinical manifestation is dysentery and neutrophils are also seen on microscopic examination of the stool which indicate the fact that an inflammatory response has been invoked in the intestinal cells . This toxin can also prove to be lethal because it can lead to a condition which is referred to as the “haemolytic uremic syndrome” . This condition results when the bacteria escapes the gastrointestinal tract and enters the systemic circulation. It leads to haemolytic anaemia, failure of the kidneys as well as reduction in the amount of circulating platelets. Escherichia Coli possesses a cell wall lipopolysaccharide which acts as an endotoxin. This endotoxin can result in pyrexia, reduced blood pressure as well as disseminated intravascular coagulation. Thus even enterotoxins produced by Escherichia Coli can result in conditions which differ from each other to an extent that two toxins lead to watery diarrhoea but verotoxin can lead to not only bloody diarrhoea but also result in a condition referred to as “haemolytic uremic syndrome” which can prove to be fatal. The endotoxin on the other hand leads to pathologies which differ from the entertoxins and are not related to the gastrointestinal tract. Pseudomonas aeruginosa is another bacterium which is also classified as a gram negative rod but its effect is not related much to the enteric tract. The toxins of this bacterium include endotoxin, exoenzyme S and exotoxin A. The endotoxin of pseudomonas is responsible for leading to spread of infection in the bloodstream. If not treated, this sepsis can result in shock. It can lead to fever, low blood pressure and disemminated intravascular coagulation The exoenzyme A has a role in disturbing the normal functioning of the phagocytes of the human body. The sites where the activities of the phagocytes is altered includes the vascular circulation as well as the internal organs present in the human body. This mechanism is considered to be of assistance for the pseudomonas aeruginosa to invade the body and hence lead to infections and pathologies. The exotoxin A is the most prominent amongst the toxins of this bacterium. This exotoxin directly affects the protein forming machinery of cells in the human body. It performs this action by adding a ADP ribosyl unit to the elongation factor 2 which leads to a halt in the formation of protein in the cell under attack. The Exotoxin A leads to infection at the site where the bacteria has colonized. This is presented as necrosis of the area and this serves to attract more bacteria to this site. It can also result in affecting the systems of the body. The exotoxin A can lead to pneumonia. Exotoxin A can also prove to be fatal for animals as well. It is also found out that pseudomonas aeruginosa can lead to a more active form of pneumonia in patients who have been infected with a toxin containing strain of this organism. Hence, this organism also proves to clarify the fact that different toxins provide for the characteristics of the resulting pathologies. Toxins are produced by different bacteria. These toxins assist the microorganisms in infecting and invading the body and resulting in the clinical manifestations of these infectious agents. Different microorganisms may produce more than one toxin. These toxins can have similar as well as varying effects. Staphylococcus aureus, pseudomonas aeruginosa and Escherichia coli provide examples of certain bacteria which produce different toxins and each of these toxins invade the human body in a unique way and lead to specific clinical pictures. It can hence be said that it is the type of toxin which determines the characteristics of the disease. REFERENCES: Top of Form Brooks, G. F., Butel, J. S., Morse, S. A., & Jawetz, E. (2004). Jawetz, Melnick, & Adelbergs medical microbiology. Lange medical book. New York, N.Y: Lange Medical Books/McGraw-Hill, Medical Pub. Division. Bottom of Form Top of Form Levinson, W. (2008). Review of medical microbiology and immunology. New York: McGraw-Hill Medical. Todar, K. (2004). Todar’s online textbook of bacteriology. University of Wisconsin, Madison Department of Bacteriology. Retrieved from http://www.textbookofbacteriology.net/pseudomonas.html Bottom of Form Read More