Describe antibiotic resistance in bacteria
Assign resistance to the bacterium and the specified drug.
Exam scope and assessment notes
Core and Extended · Biology 0970, 2026–2028. Use the stated specimen features and evidence. Diagrams are schematic. Written practice is self-checked; human subject-teacher review, supervised practical competence and cumulative assessment remain pending. Cambridge states that IGCSE 0970 has the same subject content as IGCSE 0610, with 9–1 grading. This StudyForA pathway maps the 2026–2028 syllabus only. This 9–1 graded qualification is available only in a limited number of administrative zones. Confirm that your centre can enter you for this code and exam series with Cambridge International. Cambridge has published a separate syllabus for 2029. StudyForA has not reconciled that version yet; this page supports exams in 2026, 2027 and 2028 only.
Before you begin
- Distinguish bacteria from viruses; recall enzymes, chemical reactions, pathogens and reproduction of bacteria.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which entity is antibiotic-resistant in this account?
What you will learn
- Identify survival despite a particular antibacterial treatment
- Explain reduced effectiveness without claiming resistance to every drug
Describe antibiotic resistance in bacteria
| Feature | Meaning |
|---|---|
| Susceptible strain | Controlled by the specified antibiotic |
| Resistant strain | Can survive or grow despite that antibiotic |
| Consequence | Reduced drug effectiveness against that strain |
| Not implied | Host-body resistance or resistance to every other antibiotic |
Further reading: CDC explanation of antimicrobial resistance.
Identify survival despite a particular antibacterial treatment
Some bacteria are resistant to particular antibiotics. Resistance means that the specified antibiotic does not control those bacteria as expected, so they can survive or continue growing under the relevant conditions. The resistant entity is the bacterium, not the person’s body becoming resistant. The consequence is reduced effectiveness of that antibiotic against an infection caused by those bacteria.
Susceptibility and resistance are relative to a particular drug or drug group. A strain resistant to antibiotic A is not automatically resistant to every other antibiotic. Nor does one susceptible strain establish that all bacteria of the same broad type will respond identically. Use the strain and antibiotic labels in a supplied table before predicting an effect.
Explain reduced effectiveness without claiming resistance to every drug
In a simplified model with susceptible and resistant bacteria exposed to antibiotic A, the susceptible group is killed while the resistant group survives. That contrast illustrates why an infection containing resistant bacteria may not be eliminated by A. It does not require the host to have repeatedly taken the drug: resistant bacteria can also be acquired through transmission.
A genuine laboratory susceptibility test needs standardised conditions and professional interpretation. The written course uses stated model identities and outcomes instead of asking learners to grow pathogens or handle antibiotics. Describe the resistance and reduced effectiveness using the supplied evidence; the Supplement lessons later explain changes in population proportions through selection and reproduction.
Pause and explain
If a strain is resistant to A, what follows about B?
Worked example
Strain R survives antibiotic A; strain S is killed. Describe the contrast.
Show the worked solution
- R is resistant to A under the stated conditions.
- S is susceptible to A.
Answer R is resistant to antibiotic A; S is susceptible to it. A is less effective against R.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Describe what antibiotic resistance means for a specified bacterial strain and drug.
Give me a hint
Include both survival or growth and reduced effectiveness.
Compare my reasoning
- The strain is not controlled as expected by that drug.
- It may survive or continue growing, reducing treatment effectiveness.
The bacterial strain can survive or continue growing despite the specified antibiotic, reducing that antibiotic’s effectiveness against it.
Look for these in your work
- Assign resistance to bacteria
- Connect survival with reduced effectiveness
A kills strain S but not strain R. Classify both and state the implication for A.
Give me a hint
Use response to the same drug.
Compare my reasoning
- S is susceptible; R is resistant.
- A is less effective against R.
S is susceptible to A; R is resistant to A. A is less effective against R.
Look for these in your work
- Classify both strains
- State the drug-specific consequence
Correct: a person who has never taken A cannot acquire bacteria resistant to A, and all other antibiotics must also fail.
Give me a hint
Separate transmission and drug-specific response.
Compare my reasoning
- Resistant bacteria can be acquired through transmission.
- Response to other antibiotics needs separate evidence.
A person can acquire bacteria already resistant to A. Resistance to A alone does not establish resistance to every other antibiotic.
Look for these in your work
- Allow transmitted resistance
- Avoid unsupported all-drug claims
Common mistakes
- Calling the patient’s body the resistant bacterium.
- Assuming resistance to A means resistance to all antibiotics.
What can you explain now?
If a strain is resistant to A, what follows about B?
Compare with the explanation
Its response to B needs separate evidence
Resistance is drug-specific.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Describe bacterial resistance and correct both the host-body and all-antibiotic misconceptions.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.