# A patient is prescribed a course of antibiotics to treat a bacterial infection. After a few days, the patient begins to feel better and stops taking the antibiotics early. Explain why stopping a course of antibiotics early can lead to antibiotic-resistant bacteria developing in the population.

> Pearson Edexcel A-Level Biology A (9BI0) — 5.4 Antibiotics and resistance · Explain · 5 marks

> Antibiotic resistance is an increasing global health concern. Doctors advise patients to always complete a full course of antibiotics, even if they feel better before the course has ended.

## Mark scheme (5 marks)

1. Some bacteria in the infection may have a random mutation that makes them less susceptible / resistant to the antibiotic
2. If the course is stopped early, not all bacteria are killed / some resistant bacteria survive
3. The surviving resistant bacteria reproduce / multiply, passing on the resistance gene / mutation to offspring
4. Natural selection means resistant bacteria have a survival advantage / are more likely to survive and reproduce than non-resistant bacteria
5. Over time the proportion of resistant bacteria in the population increases, so the antibiotic becomes less effective / ineffective at treating the infection

## Key terms

- [antibiotic](https://www.gradenine.co.uk/glossary/antibiotic)
- [antibiotic-resistant bacteria](https://www.gradenine.co.uk/glossary/antibiotic-resistant-bacteria)
- [population](https://www.gradenine.co.uk/glossary/population)

## Related

- [Revision notes for Pearson Edexcel A-Level Biology A (9BI0)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-patient-is-prescribed-a-course-1c149703) · Published by Druglandscape Ltd.