(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!

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(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.

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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 a bacterial communicable disease causing stomach ulcers.

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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Key points Source of information is based on textbooks & syllabus-specifications for students taking the AQA GCSE, Edexcel GCSE and OCR GCSE level biology examinations (~US grades 9-10).

Key points about Cholera and Tuberculosis

Bacterial Pathogen Communicable Diseases: Cholera & Tuberculosis

1. What Are Bacterial Diseases?

• Caused by pathogenic bacteria — single-celled prokaryotic organisms.

• Bacteria reproduce rapidly and often cause illness by:

  • Releasing toxins.

  • Damaging host tissues.

  • Triggering immune responses.

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Cholera

Pathogen: Vibrio cholerae

Transmission:

• Waterborne: Spread through contaminated water or food.

• Common in areas with poor sanitation and unsafe drinking water.

Symptoms:

• Severe watery diarrhoea

• Dehydration

• Vomiting

• Muscle cramps

• Can lead to shock and death if untreated.

How It Works:

• The bacterium produces a toxin that causes the small intestine to release chloride ions.

• Water follows by osmosis, leading to massive water loss from the body.

Treatment:

• Oral Rehydration Therapy (ORT): A solution of salts and sugars to replace lost fluids.

• Antibiotics: In severe cases, to reduce the duration of illness.

• Prevention:

  • Access to clean water.

  • Proper sanitation and hygiene.

  • Vaccination in high-risk areas.

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Tuberculosis (TB)

Pathogen: Mycobacterium tuberculosis

Transmission:

• Airborne droplets: Spread when an infected person coughs or sneezes.

• Close contact in crowded or poorly ventilated spaces increases risk.

Symptoms:

• Persistent cough (often with blood)

• Chest pain

• Fever and night sweats

• Fatigue

• Weight loss

How It Works:

• Bacteria infect the lungs, causing tissue damage.

• Can spread to other organs if untreated.

Treatment:

• Long-term antibiotic course (usually 6 months or more).

• Common drugs: Rifampicin, Isoniazid.

• Directly Observed Therapy (DOT) may be used to ensure patients complete treatment.

Prevention:

• BCG vaccine (Bacillus Calmette–Guérin) for high-risk individuals.

• Isolation of infected individuals.

• Good ventilation and respiratory hygiene.

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Why Is This Important in Human Biology?

• Highlights how different bacteria affect different body systems (digestive vs. respiratory).

• Reinforces the importance of hygiene, sanitation, and vaccination.

• Shows how antibiotics work and why completing treatment is vital to prevent resistance.

• Links to public health, epidemic control, and global health challenges.

• Encourages understanding of disease transmission, immune response, and preventative medicine.

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Quick Comparison Table

Keywords, phrases and learning objectives for this part on the bacterial pathogens cholera bacterium and Tuberculosis (TB)

Be able to describe the communicable disease infection of Cholera from the Vibrio cholerae bacteria.

Be able to describe the communicable disease tuberculosis TB from the Mycobacterium tuberculosis bacterium.

Be able to describe how cholera and TB infections are transmitted, their characteristic symptoms and treatment of the disease.

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