Y12 AS - Cholera discussion

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Discuss how cholera can be contracted, treated and how the bacterium effects the intestinal function.

Posted: 18-11-09 22:16 by Mike McNicholas

Cholera can be contracted through contaminated food and drinking water. It is caused by the vibrio cholrae bacteria. It can be treated by oral rehydration solution which rehydrates cholera sufferers from the water they had lost due to diarrhoea. The bacterium affects the intestinal function because it prevents water being absorbed back into the body, which consequently causes the sufferer to have diarrhoea which can vary from mild to very severe depending on the infection.

Posted: 21-11-09 18:01 by Kerry Foulger

the vibrio cholera infects the epithelial cells causing the sodium ions in the cells flood into the blood and this causes water to move into the blood by osmosis since the blood now has a higher solute concentration and a lower water concentration than the cells. thus causing dehydration diarrhoea.

ORS is a mixture of Glucose salt and water which has a higher water potential than the infected cells this creates a concentraion gradient allowing water to go back into the cells.

the contaminated food must have come into contact with the faeces of an chlorea infected person for the food or water ( e.g human waste being used as fertiliser or a leak in a sewage pipe) to become intaminated.

Posted: 25-11-09 01:30 by matthew tumelty

Cholera is contracted when people eat food or drink water that has been contaminated with ***** matter (excreted waste) containing Vibrio cholerae.

Cholera is treated by ORS - oral rehydration solution which is a mixture containing the correct concentration of water- to rehydrate the tissues, sodium- to replace the sodium ions lost from the epithelium of the intestine, glucose- to stimulate the uptake of sodium ions from the intiestine and to provide energy also potassium- to replace lost potassium ions and to stimulate appetite and other electrolytes (cholride and citrate ions)- to help prevent electrolyte imbalance. ORS works as;

  • If both sodium ions and glucose are present the bind to the sodium-glucose co-transporter protein. Transport only works if both molecules are present, which is why salt alone is not an effective treatment.
  • The transporter protein carries the sodium ions and glucose into the cell, down their concentration gradients.
  • This then lowers the water potential inside the epithelial cells.
  • So water diffuses from the lumen into the epithelial cells by osmosis, rehydrating the cells.

Cholera bacterium vibrio cholerae effects the intestinal function as the toxin prevents chloride ion exchange, which leads to preotein channels being kept open and chloride ions flood the intestine lumen lowering the water potential, the water then moves out of the blood across the epithelium intestine lumen- by osmosis. Treatment for this involves utilization of an alternative carrier protein system.

Posted: 29-11-09 12:42 by Abbie Craven

Good reply Abbie. You extended Matthew's ORS part well.

Both you and kerry have discussed the intestinal function and linked it to infection - your answer takes Kerry's on a stage. Again well done.

Can anyone go one better?

Posted: 29-11-09 20:48 by Mike McNicholas

THIS COMMENT IS FROM ADAM HELSTRIP... please feel free to comment...

Cholera is transmitted by the ingestion of water, or more rarely food, which has been contaminated by faecal material containing the pathogen. Such contamination can arise because:
Drinking water is not properly purified,
Untreated sewage leaks in to water courses,
Food is contaminated by people, who prepare it and serve it,
Organisms, especially shellfish, have fed on untreated sewage released in to rivers or the sea.
Vibrio cholerae bacteria ingested by humans are killed by the acidic conditions in the stomach; however there may be few that survive especially if the Ph of the stomach acid is above 4.5
When the surviving bacteria reach the small intestine they use their flagella to propel themselves in a corkscrew-like fashion, through the mucus lining of the intestine wall.
They then start to produce a toxin protein, this protein has two parts, one binds to the specific carbohydrate receptors on the cell surface membrane. As only the cells of the small intestine have these receptors, the cholera toxin only affects this region of the body. The other (toxin part) enters the epithelial cell this causes the ion channels of the cell surface membrane to open, so that the chloride ions that are normally contained within the cells to flood in to the lumen of the intestine.
The loss of chloride ions from the epithelial cells raises their water potential, while the increase of the chloride ions in the lumen of the intestines lowers its water potential; water therefore flows from the cells into the lumen.
The loss of ions from the epithelial cells establishes a concentration gradient, ions therefore move by diffusion into the epithelial cells from the surrounding tissues, including the blood. This then establishes a water potential gradient that causes water to move by osmosis from the blood and other cells/tissues into the intestine.
It is this loss of water from that causes the symptoms of cholera.

The main symptom of cholera is diarrhoea; this is an intestinal disorder in which watery faeces are produced frequently. The causes include:
Damage to the epithelial cell lining the intestine,
Loss of Microvilli due to toxins,
Excessive secretion of water due to toxins, this leads on to dehydration, then even death.

Cholera can be treated in different ways. The main way of treating cholera and other diseases that cause diarrhoea, is by oral rehydration therapy.
Oral rehydration therapy is one of the best ways to rehydrate the patient of the diarrhoeal disease. Oral rehydration solutions contain water, but just pure water is not effective for two reasons;
One because water is not being absorbed from the intestine, instead it is being lost from the cells of the intestine,
And two because drinking water does not replace the electrolytes that are being lost from the epithelial cells of the intestine.

Oral rehydration solutions are effective because they not only rehydrate the patient they also replace the electrolytes lost, the ORS contains,
Water to rehydrate tissues,
Sodium to replace the sodium ions lost from the epithelium of the intestine and to make optimum use of the alternative sodium-glucose carrier proteins,
Glucose to stimulate the uptake of sodium ions from the intestine and to provide energy
Potassium to replace lost potassium ions and to stimulate appetite,
Other electrolytes such as chloride and citrate ions, to help prevent electrolyte imbalance.
It is possible to replace water and electrolytes intravenously by a drip, but this requires trained personnel, and this may not be available in developing countries.

these ingredience are mixed and can be mixed with boiled water to make the solution, this method of treating cholera can be administeated by people with minimal training. the solution must be given in large amounts, through out the illness.

this method of treatment only rehydrates the patient, other means may be needed to cure the illness.

Posted: 03-12-09 00:03 by Mike McNicholas

thanks sir, finally its letting me post comments :)

Posted: 04-12-09 01:52 by Adam Helstrip

I have no feedback to 'feed' on cholera. I haven't a clue. So, i think ill sit and make notes from everyone else's feedback. Then get back to you. :)

Posted: 05-01-10 19:03 by danielle pace