Knowing an antibiotic's class is different from deciding whether it is appropriate for a patient. The organism, infection site, severity, patient factors and available evidence all affect that decision. A susceptibility result is useful, but it is not a complete prescription.
This quiz combines sixteen original questions about mechanisms and clinical choices. The cases are fictional and framed mainly around adult UK practice, with the source and limits of each explanation made explicit. They are not a substitute for current local antimicrobial guidance, microbiology advice or individual assessment.
World AMR Awareness Week runs from 18 to 24 November 2026, providing an opportunity for a team discussion. This is an independent iatroX educational activity, not an official WHO quiz, and the questions remain useful beyond the campaign week.
Round 1: connect the drug to the mechanism
Choose the most precise answer. Recognising a class should not be taken as permission to substitute its members indiscriminately.
1. Penicillins and their target
Do penicillins principally interfere with bacterial cell-wall synthesis, viral uncoating or mammalian histamine receptors?
2. The tetracycline binding site
Tetracyclines inhibit bacterial protein synthesis through interaction with which ribosomal subunit: 30S or 50S?
3. The macrolide contrast
Macrolides also inhibit bacterial protein synthesis. Which ribosomal subunit is the principal target in the conventional mechanism description?
4. A sequential pathway
Trimethoprim and a sulfonamide act at different steps in the same bacterial metabolic pathway. Which pathway links their actions?
Round 2: spectrum is not a synonym for suitability
5. A target the organism does not have
Why are beta-lactam antibiotics unsuitable for treating Mycoplasma pneumoniae itself, despite their usefulness against many other bacterial causes of respiratory infection?
6. The culture allows a narrower choice
An inpatient is improving after empirical broad-spectrum treatment. Microbiology identifies the causative organism and a narrower active option that is appropriate for the infection site and the patient's circumstances. Should broader coverage be continued solely because it was the initial prescription?
Round 3: stewardship decisions
7. An uncomplicated cough
A well adult has a short history of cough following a viral respiratory illness. Clinical assessment identifies no pneumonia, important deterioration or other current indication for antibiotics. Does a cough becoming inconvenient create an antibiotic indication by itself?
8. A culture without symptoms
A healthy, non-pregnant woman has a positive urine culture obtained without a clear clinical indication. She has no urinary symptoms or systemic illness and no planned invasive urological procedure. Should the culture alone trigger treatment?
9. The allergy label needs a history
A record says "penicillin allergy". The patient recalls nausea during a previous course but has no known history of rash, swelling, respiratory symptoms or collapse. Should this be documented as confirmed anaphylaxis, or should the reaction history be clarified through the appropriate prescribing and allergy-assessment process?
10. Review the intravenous route
An adult has received intravenous antibiotics for approximately forty-eight hours. They are improving, can absorb and take oral medication, and have an appropriate oral option. No infection requiring a special prolonged intravenous strategy has been identified. Should the route remain intravenous automatically until discharge?
11. The urinary isolate and the infection site
A patient has fever, flank pain and a presentation concerning for upper urinary tract infection. A urine isolate is reported susceptible to nitrofurantoin. Does that laboratory result make nitrofurantoin an appropriate treatment for suspected pyelonephritis?
12. New diarrhoea during treatment
A patient develops frequent new watery diarrhoea during an antibiotic course, with abdominal discomfort. Should the clinician simply add an antidiarrhoeal medicine and ignore the antibiotic exposure, or assess for causes including C. difficile and review the treatment?
13. A systemic fluoroquinolone as the convenient default
A clinician considers a systemic fluoroquinolone even though another commonly recommended antibiotic is suitable. Under the MHRA restriction, is convenience alone sufficient to make the fluoroquinolone the default choice?
14. The diagnosis changes
Antibiotics were started while a possible infection was being assessed. Subsequent clinical review establishes a non-infective explanation and no remaining indication for antibacterial treatment. Must the original course still be completed simply because it was started?
15. Cultures and a deteriorating patient
A patient is acutely deteriorating with suspected serious bacterial infection. Appropriate cultures are desirable, but obtaining them is becoming difficult. Should a prolonged attempt to obtain samples delay urgently indicated antimicrobial treatment and resuscitation?
16. The incomplete antimicrobial plan
The prescription is legible and the dose has been checked, but the notes do not explain the indication, intended duration or review point. What is the most useful addition to make the plan assessable by the next clinician?
Answers: mechanisms and spectrum
1. Bacterial cell-wall synthesis
Penicillins interfere with peptidoglycan cross-linking through penicillin-binding proteins. They do not treat a viral illness by acting on a viral equivalent of that structure. See OpenStax's antibacterial mechanisms.
2. The 30S subunit
Tetracyclines act at the 30S subunit and interfere with aminoacyl-tRNA binding. Naming a shared ribosomal target does not make all protein-synthesis inhibitors the same class. See antibacterial mechanisms.
3. The 50S subunit
Macrolides act at the 50S subunit. This distinguishes their conventional mechanism from that of tetracyclines, while leaving important drug-specific properties to be assessed separately. See antibacterial mechanisms.
4. Folate metabolism
Sulfonamides and trimethoprim interrupt different steps in bacterial folate synthesis and processing. The relationship is sequential inhibition, not two names for an identical target. See antibacterial mechanisms.
For another mechanism-based activity, clinical connections asks players to find precise relationships among sixteen concepts. Its daily subject matter is mixed clinical science, not a guaranteed antimicrobial edition.
5. Mycoplasmas lack the relevant cell wall
The CDC's clinical guidance states that mycoplasmas lack a cell wall and are inherently resistant to beta-lactams. An antibiotic needs an applicable target; a broad reputation cannot supply one. Selection among alternatives still depends on the patient, setting and resistance information.
6. No: review and narrow when appropriate
The question supplies a suitable narrower option. Initial empirical coverage is not a reason to retain unnecessary breadth after review. UKHSA's Start Smart Then Focus toolkit supports reassessing and amending treatment using the clinical and microbiological information.
Answers: clinical decisions
7. No: inconvenience is not a new indication
The scenario states that assessment has not identified a reason for antibiotics. Explain the expected course, symptom measures and reasons for reassessment rather than prescribing solely because the cough is unwelcome. The NHS cough guidance distinguishes common self-limiting presentations from those needing further assessment or treatment.
The important qualification is that the patient has actually been assessed. The answer is not a blanket rule that every cough is viral or that deterioration should be ignored.
8. No: avoid treating this result alone
The IDSA asymptomatic-bacteriuria guideline recommends against treatment in healthy non-pregnant women without an applicable exception. Pregnancy and specified invasive urological procedures change the assessment, which is why the stem makes those circumstances explicit.
This US professional guideline supports the stated clinical principle; local UK pathways still govern implementation. New symptoms would require reassessment rather than permanent attachment of an "asymptomatic" label.
9. Clarify the reaction rather than relabelling it by assumption
Nausea can be a non-allergic adverse effect and is not equivalent to anaphylaxis. The NHS antibiotic side-effect guidance distinguishes gastrointestinal effects from allergic features.
Establish the medicine, timing, symptoms, severity and subsequent exposures. This question does not authorise an unsupervised drug challenge or automatic deletion of an allergy label from an incomplete account. A reliable history should inform the appropriate assessment and prescribing decision.
10. Review for an appropriate intravenous-to-oral switch
The UKHSA adult IVOS criteria support considering the route within forty-eight hours and reviewing regularly thereafter.
Improvement, gastrointestinal function, a suitable oral agent and the infection being treated matter. The stem excludes a known special intravenous indication; it does not imply that every bloodstream or deep-seated infection can be switched using this abbreviated case. The route is a decision to reassess, not an automatic marker of treatment quality.
11. No: the site still matters
The MHRA nitrofurantoin advice states that it should not be used for suspected upper urinary tract infection or sepsis secondary to a urinary infection.
An in-vitro susceptibility result does not establish adequate treatment of the involved tissues. Assess severity and use an appropriate pathway and agent for the clinical presentation. The question deliberately tests site suitability, not a renal-function threshold.
12. Assess the diarrhoea and review the antibiotic
Antibiotic exposure is relevant to possible C. difficile infection, but it does not prove that every episode of diarrhoea has that cause. Assess severity, hydration and the need for testing, infection-control measures and treatment review. See NHS C. difficile guidance.
Simply suppressing the symptom can miss the clinical problem. Equally, the clinician should not replace one automatic assumption with another; the diagnosis and ongoing need for the original antibiotic require assessment.
13. No: other recommended options must be inappropriate
The MHRA fluoroquinolone restriction limits systemic use to situations in which other commonly recommended antibiotics are inappropriate. The warning concerns potentially serious, prolonged adverse effects.
This restriction was introduced in January 2024; it is not a new November 2026 announcement. A clinician should document why the chosen treatment is appropriate rather than treating convenience or familiarity as a substitute for that judgement.
14. No: an appropriate clinical review can stop treatment
When no indication remains, continuing merely to finish the original plan is not required. Start Smart Then Focus includes cessation after reassessment. This is a clinician-led change with explanation, not advice for patients to stop prescribed treatment without discussing it.
15. No: do not create an unsafe delay
Obtain relevant cultures before treatment where practicable, but not at the expense of urgently needed care. The UKHSA inpatient toolkit links appropriate sampling with prompt treatment of severe infection. Continue resuscitation, escalation and investigation in parallel.
16. Add the indication and an explicit review or stopping plan
Record why treatment is being given, the intended duration or review point, and how the decision will be revisited. The UKHSA toolkit supports that documentation. A checked dose alone does not communicate the whole antimicrobial plan to the receiving team.
Debrief the distinction that changed the answer
The sixteen questions address several different problems. Some concern a drug target, some the limits of a laboratory result and others the timing of reassessment. They should not all be reduced to the message "use fewer antibiotics".
A useful teaching response identifies what changed the decision. In question 6, it is new information supporting a suitable narrower option. In question 11, it is the infection site despite the susceptibility result. In question 14, it is the loss of the original indication after assessment.
For each case, ask what additional fact could change the answer. Do not alter the conclusion merely to preserve a general slogan. Appropriate antimicrobial use includes starting effective treatment when needed as well as withholding or stopping it when it is not.
Use a shorter teaching selection
For a brief meeting, use questions 1, 5, 8, 10, 11 and 16. This combines a mechanism, an organism-specific limitation and four different clinical decisions.
Ask participants to write an answer privately before discussing it. After the explanation, ask someone else to describe the rule in a new sentence rather than repeat the wording on the page.
The clinical teaching guide offers additional facilitation ideas. A teacher should recheck the clinical guidance before a future session, particularly where local susceptibility patterns or pathways affect a management choice.
Continue with a different daily task
stat provides three independent UK-context decisions about priorities, next steps and plan review. clinical connections provides a grouping puzzle with explanations and an optional application question.
Neither promises that today's edition is an antibiotic quiz. This article supplies the antimicrobial-specific exercise itself, while the games provide another complete challenge for readers who enjoy the format.
Frequently asked questions
Can this quiz replace my local antimicrobial guideline?
No. It tests selected principles. Actual treatment depends on the patient, infection site, severity, local guidance and appropriate specialist or microbiology advice.
Are the scenarios taken from today's iatroX games?
No. They are original article exercises. The daily games have separate mixed clinical editions and are not guaranteed to cover antimicrobials on a particular date.
Which game fits readers who preferred the mechanism questions?
clinical connections is the relevant grouping activity. Readers who preferred choosing an action can try stat. Neither score establishes prescribing competence.
Find a fresh set of clinical relationships in today's puzzle