UK GCSE level age ~14-16, ~US grades 9-10 Biology revision notes re-edit 16/05/2023 [SEARCH]

 Communicable diseases: 5. Examples of bacterial pathogen communicable diseases - Cholera bacterium and Tuberculosis (TB)

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(5) Examples of bacterial pathogen communicable diseases

(5a) Cholera is from a bacterium called Vibrio cholerae

Cholera bacteria cause diarrhoea and in severe cases causes dangerous fluid loss - severe dehydration, which can cause complications which can be fatal.

What does the cholera pathogen do?

The cholera bacterium produces a toxin that causes secretion of chloride ions into the small intestine, reducing the water potential.

Therefore this causes osmotic movement of water into the gut, causing diarrhoea, dehydration and loss of salts from blood.

Cholera is a serious medical condition, with many fatalities to this day in poor countries where people do not have access to clean potable drinking water fit for human consumption.

The main symptom of diarrhoea, passing watery faeces, persists for a few days.

The diarrhoea can be treated using oral rehydration therapy.

A type of fluid replacement used to prevent and treat dehydration, especially due to diarrhoea.

It involves drinking water with modest amounts of sugar and salts, specifically those salts of sodium and potassium e.g. their chlorides and citrates.

The principal source, and cause of spreading, is contaminated water supply containing the cholera bacterium, which is the means by which the cholera bacteria are spread.

Poor hygiene further contributes to the spread of the infection because faeces contain the cholera bacteria too.

Cholera is most prevalent in developing countries where clean water is in limited supply - if at all.

Therefore, prevention is best obtained by using a clean water supply - there were outbreaks of cholera in Victorian England until it was realised the source of the infection was dirty water!


(5b) Tuberculosis (TB) is from a bacterium called Mycobacterium tuberculosis

The effects and symptoms of the tuberculosis bacteria infection include coughing and lung damage - older people can be severely weakened and further medical complications may arise - one disease can be compounded with another.

The bacteria are conveyed through the air when infected people cough or sneeze out droplets containing the bacterium - note that coughing and sneezing are the principal symptoms!

Ways to minimise the spread of tuberculosis infection

Infected people should minimise contact with people - avoid crowded places, sleep alone.

Although we all should, it is particularly important that a TB infected person should practice good hygiene - like coughing or blowing nose into tissues and carefully disposing them, washing hands regularly, wearing a face mask if near people, and keeping the house well ventilated also reduces the chances of transmission.


Stomach ulcers can be caused by the bacterium Helicobacter pylori

The disease, pathogen, symptoms-effects, means of spread and how to reduce or prevent transmission for XYZ bacterial communicable disease.

Stomach ulcer symptoms and effects include stomach pain, nausea and vomiting.

The bacteria reduce the stomach's defences against the acid it produces to digest food and causes inflammation of the stomach lining and damaging it.

The stomach acid (quite concentrated hydrochloric acid) penetrates the stomach lining creating a hole (the ulcer) that exposes the stomach tissue

The bacteria are ingested after eating contaminated food or drinking contaminated water - referred to as an example of oral transmission.

The chances of getting a stomach ulcers by transmission are greatly reduced by having access to clean water and watching your personal hygiene e.g. washing hands when going to the toilet, disinfecting food preparation spaces and a clean house - especially the bathroom and kitchen.

Treatments for stomach ulcers include the use of antibiotics and drugs that reduce stomach acid production.


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