AMC MCQ Infection Questions: 10 Free Practice MCQs
Infection questions test source control, the right specimen and the right antibiotic. The AMC MCQ expects you to recognise sepsis, choose empirical cover from Australian guidance, and review it when cultures return. Tropical and imported infection appears more often than in UK exams, including dengue, malaria and tuberculosis. The blueprint also tests infection control, needlestick management and antimicrobial stewardship.
Where candidates lose marks
- Starting antibiotics without taking cultures when the patient is stable enough to allow it.
- Forgetting source control in an abscess, an infected joint or an obstructed urinary tract.
- Missing a notifiable disease or an infection that needs public health notification.
- Continuing broad spectrum antibiotics after sensitivities allow de-escalation.
Guideline to follow: The AMC MCQ follows eTG Antibiotic, the Australian national notifiable diseases guidance and the Antimicrobial Stewardship Clinical Care Standard.
Ten AMC MCQ-style infection questions with the answer and the reasoning behind it. They come from the AU.med bank, which has 71 infection questions and many more across every topic.
1 / 10
A 19-year-old university student presents to her GP with a 5-day history of sore throat, fever, and profound lethargy. Physical examination reveals tonsillar hypertrophy with exudates, palatal petechiae, and tender posterior cervical lymphadenopathy. Abdominal exam shows mild splenomegaly.
What is the most likely diagnosis?
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Answer: A. Infectious mononucleosis (Glandular fever)
Why: Infectious mononucleosis (glandular fever) is most commonly caused by the Epstein-Barr virus (EBV). The clinical presentation of fever, pharyngitis, exudative tonsillitis, splenomegaly, and symmetric posterior cervical adenopathy in a young adult is classic. Diagnostic tests include the monospot test (heterophile antibodies) and atypical lymphocytosis on FBC.
- B. While streptococcal infection causes sore throat and exudates, splenomegaly and posterior cervical lymphadenopathy are highly characteristic of glandular fever.
- C. Acute HIV can present with a mononucleosis-like syndrome, but is less common and usually features a maculopapular rash and painful mucocutaneous ulcers.
- D. Diphtheria is rare in immunized populations and presents with a thick, gray pseudomembrane that bleeds on scraping.
Sources: eTG complete, Infectious Diseases; RACGP Glandular Fever Management
2 / 10
A 24-year-old man undergoes a lumbar puncture for suspected meningitis. The cerebrospinal fluid (CSF) results show: Opening pressure 280 mmH2O (normal 100-200), Polymorphonuclear leukocytes (Neutrophils) 850 cells/uL (normal < 5), Lymphocytes 20 cells/uL (normal < 5), Protein 2.1 g/L (normal 0.15-0.45), Glucose 1.2 mmol/L (simultaneous blood glucose 6.2 mmol/L).
Which of the following is the most likely etiology of this patient's meningitis based on the CSF findings?
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Answer: A. Bacterial meningitis (e.g., Neisseria meningitidis)
Why: Bacterial meningitis is characterized by: 1) high opening pressure; 2) marked neutrophilic pleocytosis (usually > 1000 cells/uL); 3) significantly elevated protein (due to blood-brain barrier disruption); and 4) decreased glucose (CSF/blood glucose ratio < 0.4). This profile helps differentiate it from viral (lymphocytic, normal glucose) and tuberculous/fungal (lymphocytic, low glucose) causes.
- B. Viral meningitis characteristically presents with lymphocytic pleocytosis and normal CSF glucose levels.
- C. Fungal meningitis typically presents with lymphocytic pleocytosis, not a neutrophil-predominant reaction.
- D. All parameters (pressure, white cells, protein, glucose ratio) are severely abnormal in this CSF report.
Sources: eTG complete, Infectious Diseases, Meningitis; Queensland Health Meningitis Clinical Pathway
3 / 10
A GP receives a positive laboratory result for Salmonella enteritidis in a stool sample from a 35-year-old food handler.
What are the GP's statutory public health notification obligations in Australia?
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Answer: D. Notify the state public health unit within the mandated timeframe for Salmonellosis.
Why: Salmonella enteritidis is a notifiable condition. In Australia, clinicians have a statutory duty to notify their state or territory public health department of designated communicable diseases to enable surveillance and outbreak control.
- A. Notifying the employer directly violates patient confidentiality.
- B. Both laboratories and clinicians have statutory duties to notify.
- C. Notification is triggered by diagnosis, not clinical severity.
Sources: State Public Health Act; National Notifiable Diseases List
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4 / 10
A 68-year-old man presents to the clinic with cough, purulent sputum, fever, and dyspnea. On examination, he is alert and oriented, BP is 125/80 mmHg, respiratory rate is 22 breaths per minute, and heart rate is 90 bpm. Chest auscultation reveals right lower lobe bronchial breathing. He has no significant comorbidities and is assessed as having mild community-acquired pneumonia (CAP).
Which of the following is the most appropriate first-line empirical antibiotic regimen according to the Therapeutic Guidelines (eTG)?
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Answer: D. Oral Amoxicillin 1g three times daily (or Doxycycline 100mg twice daily)
Why: In Australia, the empirical antibiotic choice for community-acquired pneumonia is guided by severity. For mild CAP, Streptococcus pneumoniae is the primary target. Oral Amoxicillin 1g eight-hourly is first-line. Doxycycline (100mg twelve-hourly) is an acceptable alternative, particularly if atypical pathogens (e.g. Mycoplasma pneumoniae) are suspected or if there is a penicillin allergy.
- A. Cefalexin has poor activity against Streptococcus pneumoniae and atypical pathogens, making it inappropriate for pneumonia treatment.
- B. Intravenous broad-spectrum cephalosporins are reserved for moderate-to-severe pneumonia requiring hospital admission.
- C. Fluoroquinolones are reserved for confirmed resistant infections or severe penicillin allergy to prevent the development of resistance.
Sources: eTG complete, Infectious Diseases, Community-Acquired Pneumonia; AMH
5 / 10
A 3-year-old girl has confirmed meningococcal disease after presenting with fever and a purpuric rash. She has been treated with intravenous ceftriaxone, is now haemodynamically stable and afebrile, and the organism is fully sensitive to penicillin.
What is the most appropriate duration of intravenous antibiotic treatment?
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Answer: C. 5 days of intravenous treatment
Why: Confirmed meningococcal disease requires 5 days of intravenous treatment, continuing a third generation cephalosporin until sensitivities are confirmed. Shorter courses of 24 hours or 3 days risk relapse, while 14 days is longer than necessary and prolongs hospital stay, particularly as treatment can often be completed through hospital in the home services once the child is stable and afebrile.
- A. A single day of treatment is inadequate to eradicate Neisseria meningitidis and prevent relapse in invasive disease.
- B. Three days is shorter than the recommended 5 day course for confirmed meningococcal disease.
- D. A 14 day course is longer than required and prolongs inpatient care, since confirmed meningococcal disease responds to 5 days of intravenous therapy.
Sources: The Royal Children's Hospital Melbourne, Clinical Practice Guidelines: Acute meningococcal disease (last updated May 2026)
6 / 10
A 29-year-old female dental assistant presents with a 3-day history of throbbing pain and swelling around the nail fold of her right index finger. On examination, there is localized erythema, swelling, and a visible collection of pus under the lateral nail fold.
What is the most appropriate management?
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Answer: B. Surgical incision and drainage under digital nerve block.
Why: Acute paronychia with a visible abscess requires drainage, which can be performed under local digital nerve block using a scalpel (e.g. 11 blade) or by gently elevating the lateral nail fold with a blunt probe/needle. Antibiotics are reserved for cases with spreading cellulitis or immunocompromised states.
- A. Antibiotics and warm soaks are appropriate for early cellulitis, but once an abscess forms, drainage is key.
- C. This is a bacterial infection, not herpetic whitlow, which presents with vesicles.
- D. Nail extraction is not indicated for simple paronychia unless the infection extends beneath the nail plate.
Sources: eTG Complete: Hand Infections
7 / 10
A 30-year-old woman attends her first antenatal visit at 9 weeks gestation. The clinic is arranging routine syphilis serology with her other booking blood tests, and the laboratory offers several different assays.
Which assay does RANZCOG recommend for initial syphilis screening in pregnancy?
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Answer: D. Treponema pallidum particle agglutination assay (TPPA)
Why: Routine syphilis testing is recommended at the first antenatal contact. RANZCOG advises screening with a specific Treponema pallidum assay, for example the Treponema pallidum haemagglutination assay (TPHA) or the Treponema pallidum particle agglutination assay (TPPA). The non-specific assays such as RPR or VDRL are cheaper but are less likely to detect latent infection and so are not the preferred screening approach. An IgM enzyme immunoassay is not part of the recommended initial screening strategy.
- A. Non-specific tests such as RPR are cheaper but are less likely to detect latent infection, so they are not the recommended screening assay.
- B. The VDRL test shares the limitations of other non-treponemal assays and may miss latent syphilis in pregnancy.
- C. An IgM immunoassay is not the screening test the college nominates, because screening relies on a specific treponemal assay.
Sources: RANZCOG Routine antenatal assessment in the absence of pregnancy complications (C-Obs 3b), March 2022
8 / 10
A 35-year-old woman at 12 weeks gestation is found to have hepatitis B surface antigen detected at booking. She feels well, has no jaundice and her liver function tests are reported as normal.
What is the most appropriate next step in her care?
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Answer: D. Assess hepatitis B DNA and HBe antigen status and liver function and refer for specialist support
Why: RANZCOG advises that all pregnant women should be screened for hepatitis B. A woman found to be a chronic carrier should have an assessment of her viral replicative status, including hepatitis B DNA level and HBe antigen status, together with liver function tests, and should be referred for specialist support. Delaying this work or limiting care to infant vaccination alone would leave maternal disease unassessed and miss the opportunity to reduce mother to child transmission.
- A. Postponing assessment until after birth would delay the maternal evaluation and specialist input that chronic hepatitis B in pregnancy requires.
- B. Infant immunisation is important but does not replace the maternal assessment of viral replicative status and liver function that the college recommends.
- C. Deferring assessment to the third trimester wastes the opportunity to plan antiviral and neonatal management early in the pregnancy.
Sources: RANZCOG Routine antenatal assessment in the absence of pregnancy complications (C-Obs 3b), March 2022
9 / 10
A 28-year-old pregnant woman at 14 weeks gestation is diagnosed with symptomatic bacterial vaginosis based on a fishy vaginal odour, thin greyish discharge, and the presence of clue cells on vaginal smear. Her pregnancy is otherwise uncomplicated, but she has a history of a late miscarriage at 18 weeks in her previous pregnancy.
What is the clinical significance and recommended management for this patient?
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Answer: C. Prescribe oral metronidazole 400 mg twice daily for 7 days
Why: Bacterial vaginosis (BV) in pregnancy is associated with adverse outcomes including late miscarriage, preterm pre-labour rupture of membranes (PPROM), and preterm delivery. Symptomatic pregnant women should be treated with oral metronidazole (400 mg twice daily for 7 days) or oral clindamycin. Metronidazole is safe to use in all trimesters of pregnancy.
- A. Symptomatic bacterial vaginosis in pregnancy is associated with late miscarriage and preterm birth; treatment is indicated.
- B. Azithromycin is used to treat chlamydia, not bacterial vaginosis.
- D. IV penicillin is used for intrapartum GBS prophylaxis, not for bacterial vaginosis.
Sources: eTG Complete: Vaginal Infections; RANZCOG Guidelines
10 / 10
A 32-year-old male presents with a single, painless, indurated ulcer (chancre) on the glans penis and regional lymphadenopathy during a localized syphilis outbreak.
What is the primary test for diagnosis?
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Answer: B. Swab for PCR (Treponema pallidum)
Why: Primary syphilis presents with a painless chancre. Swab of the lesion for Treponema pallidum PCR is the preferred diagnostic test in early primary syphilis because serology (VDRL/RPR and treponemal antibodies) may be negative in the first 1-2 weeks following lesion appearance.
- A. Incorrect. Viral swab (HSV PCR) tests for Herpes Simplex Virus, which presents with painful clustered vesicles and shallow ulcers.
- C. Incorrect. Blood cultures do not reliably grow Treponema pallidum and are not used for syphilis diagnosis.
- D. Incorrect. Visual inspection alone cannot differentiate syphilis from other genital ulcer etiologies without microbiological confirmation.
Sources: Australian STI Management Guidelines
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