Bacterial diseases — AQA GCSE Biology
Test yourself on Bacterial diseases with AQA GCSE practice questions.
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Bacterial diseases explained
Salmonella is a bacterium that causes food poisoning when it is swallowed in contaminated food or transferred onto food during unhygienic preparation.
Read the full explanation
The bacteria multiply in the gut and release toxins that irritate the digestive system, causing symptoms such as cramps, diarrhoea, vomiting and fever. Common sources include undercooked poultry, eggs and meat, while cross-contamination occurs when raw food touches cooked or ready-to-eat food, or when hands, boards and knives are not washed. Prevention therefore focuses on cooking food thoroughly, storing raw and cooked foods separately, washing hands and surfaces, and keeping food at safe temperatures. Most people recover, but severe cases can cause dehydration, so rehydration is important.
Your focus
- State that Salmonella is a bacterium spread by contaminated food.
- Describe how unhygienic preparation causes cross-contamination.
- Explain how cooking and hygiene measures reduce the risk of food poisoning.
Bacterial diseases exam tips
Marking Points
- Salmonella is a bacterium that causes food poisoning.
- Infection occurs when contaminated food containing the bacteria is eaten.
- Unhygienic preparation can transfer bacteria onto food, for example via hands, utensils or surfaces.
- Symptoms include diarrhoea, vomiting, cramps and fever caused by toxins.
- Prevention includes thorough cooking, hand washing, separating raw and cooked food and safe storage.
Examiner Tips
- 💡Name a specific food source such as undercooked chicken or eggs to make the answer concrete.
- 💡Use the term cross-contamination when explaining how bacteria reach ready-to-eat food.
- 💡Link each symptom to the effect of bacterial toxins on the digestive system.
Common Mistakes
- Calling Salmonella a virus; correction: Salmonella is a bacterium, so it can be treated with antibiotics in serious cases and is controlled by hygiene and cooking.
- Thinking food poisoning is caused by food going off only; correction: Salmonella can be present in food that looks and smells normal, so thorough cooking is essential.
- Ignoring cross-contamination; correction: bacteria can transfer from raw meat to salad via a chopping board, so separate boards and washing are needed.