AQA GCSE Combined Science: Trilogy Biology Paper 2 (Higher), 2018: Question 2

6 marks · High Demand difficulty · Extended Answer

Explain what advice doctors should be given to prevent the spread of a new antibiotic-resistant strain of Pseudomonas bacteria.

Practise this question

Question

The question image shows exam question 02 with text stating that Pseudomonas bacteria cause infections in hospital patients and that a new strain has evolved which can only be killed by the antibiotic fluoroquinolone. It asks students to explain the advice doctors should be given to prevent the spread of this new strain in the human population. The question is worth 6 marks and is followed by multiple blank lined spaces for an extended written response.
Question text

02 Pseudomonas bacteria cause infections in hospital patients.

A new strain of Pseudomonas bacteria has evolved. This new strain can only be

killed by one antibiotic called fluroquinolone.

Scientists want to prevent the new strain of Pseudomonas from spreading in the

human population.

Explain the advice doctors should be given to prevent the spread of the new strain.

[6 marks]

Mark scheme

Show the mark scheme The mark scheme image is a level-of-response table for question 02, with Level 3 worth 5 to 6 marks for a detailed, logically linked account, Level 2 worth 3 to 4 marks, Level 1 worth 1 to 2 marks, and 0 for no relevant content. Indicative content includes not prescribing antibiotics for mild or viral infections, ensuring patients finish the full course, only prescribing fluoroquinolone when needed for the new strain, and explaining antibiotic resistance. Additional acceptable points include handwashing, disinfecting wards, and isolating infected patients to prevent spread.

AO /

Question Answers Mark

Spec. Ref.

02 Level 3: Relevant points (advice / reasons) are identified, given in 5–6 AO2

detail and logically linked to form a clear account.

Level 2: Relevant points (advice / reasons) are identified, and there 3–4 AO2

are attempts at logical linking. The resulting account is not fully AO1

clear.

Level 1: Points are identified and stated simply, but their relevance 1–2 AO1

is not clear and there is no attempt at logical linking.

No relevant content 0

Indicative content 4.6.3.4

4.3.1.8

precautions with reasons

• do not prescribe fluroquinolone / antibiotics for mild infections

• because they will get better due to the body’s normal immune

system

• do not prescribe fluroquinolone / antibiotics for viral infections /

colds / flu

• because antibiotics do not kill viruses

• if you do prescribe fluroquinolone / antibiotics make sure the

patient finishes the course

• because any bacteria left may develop resistance, survive and

reproduce rapidly (due to lack of competition)

• only prescribe fluroquinolone if the patient has the new strain

• because routine use would lead to an increase in resistant

bacteria

other relevant content

• doctors and nurses in the practice / hospital should be using

antibacterial / alcohol hand wash between each patient and / or

disinfectant to clean wards

• to kill (resistant) bacteria

• doctors should isolate patients with this strain of bacteria

• to prevent other patients getting the resistant infection

Total 6

How to answer it

Pseudomonas: preventing spread of a resistant strain

What this question tests

Understanding how to stop the spread of antibiotic-resistant bacteria in hospitals and the community. You need to explain infection control steps, correct antibiotic use, and why these actions reduce the number of resistant bacteria.

Question 02

Explain the advice doctors should be given to prevent the spread of the new strain

6 marks — extended response

✅ Correct answers to include

  • Only prescribe fluoroquinolone when it is really needed, not for mild infections.
  • Do not use antibiotics for viral infections such as colds or flu.
  • Make sure the patient finishes the full course of antibiotics.
  • Use handwashing, disinfectant, and antiseptic/alcohol hand gel between patients.
  • Isolate patients infected with the resistant strain.
  • Explain that routine use of the antibiotic increases the number of resistant bacteria.

💡 Key knowledge

  • Antibiotics kill bacteria, but they do not kill viruses.
  • If some bacteria survive treatment, they may be resistant.
  • Resistant bacteria reproduce quickly because there is less competition.
  • Infection control in hospitals stops bacteria moving from one patient to another.

🧠 Exam technique

  • This is a “explain” question, so give a reason for each action.
  • Top answers are linked: advice → why it works → result.
  • To reach Level 3, your answer should be clear, detailed, and logically connected.
  • Use the words resistant , spread , kill , and isolate correctly.
Part (whole question)

Model full-mark answer

Doctors should only prescribe fluoroquinolone when it is necessary, because routine use will increase the number of resistant bacteria. They should not give antibiotics for viral infections such as colds or flu, because antibiotics do not kill viruses. If a patient does need the antibiotic, they should be told to finish the full course so that fewer bacteria survive to become resistant and reproduce rapidly. In hospitals, staff should wash hands and use disinfectant or alcohol gel between patients, and patients with this strain should be isolated so the resistant bacteria do not spread to other patients.

This would score highly because it gives several correct actions and explains each one. The ideas are linked in a logical chain, which is exactly what the Level 3 mark scheme asks for.
Part (whole question)

How marks are awarded

Mark scheme levels

  • Level 3 (5–6 marks): relevant points are explained in detail and linked clearly.
  • Level 2 (3–4 marks): relevant points are made, with some linking, but the account is not fully clear.
  • Level 1 (1–2 marks): simple points are stated with little or no explanation.

What separates top answers

  • They do not just list facts.
  • They explain why each action reduces spread.
  • They mention both antibiotic stewardship and infection control.
Part (whole question)

✅ Checklist for a 6-mark answer

Write at least 3–4 of these

  • Prescribe only when necessary.
  • Do not use antibiotics for viruses.
  • Complete the full course.
  • Use hygiene measures between patients.
  • Isolate infected patients.

❌ Common errors

  • Saying antibiotics kill viruses.
  • Only naming a precaution with no reason.
  • Talking about “immune system” without linking it to the question.
  • Forgetting the idea of resistant bacteria surviving and reproducing.
  • Not mentioning hospital spread / patient-to-patient transmission.
Part (whole question)

Why these measures work

📐 Step-by-step reasoning

  1. Some bacteria survive if the antibiotic is overused or not finished.
  2. Survivors are likely resistant to the antibiotic.
  3. They reproduce rapidly because there is less competition.
  4. Infection control stops resistant bacteria moving to other patients.

💡 Examiner insight

  • Students often lost marks by giving only one idea, such as “wash hands”.
  • Better answers combined drug use with hygiene and isolation.
  • The strongest responses showed a clear link between reducing unnecessary antibiotic use and reducing resistant bacteria.
Final revision

One-sentence summary

To stop the new Pseudomonas strain spreading, doctors should use fluoroquinolone only when needed, make patients finish the course, avoid using antibiotics for viral infections, and use strict hygiene and isolation so resistant bacteria cannot spread between patients.

Topics

Biology · B3: Infection and Response · B6: Inheritance, Variation and Evolution

Question and mark scheme from the AQA GCSE Combined Science: Trilogy examination, Biology Paper 2 (Higher), 2018. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.