Serious & Notifiable Infections Practice Questions

Q: A 45-year-old woman with miliary tuberculosis is started on standard four-drug therapy. After 3 weeks of treatment, she develops confusion, ataxia, and ophthalmoplegia. Her serum sodium is 128 mmol/L, ALT is 45 U/L (baseline 35 U/L), and serum lactate is 4.2 mmol/L. Brain MRI shows bilateral symmetrical lesions in the mamillary bodies and thalamus. Which anti-tuberculous drug is most likely responsible for this presentation?

Isoniazid. ***Isoniazid*** - **Isoniazid** can cause **Wernicke's encephalopathy** (confusion, ataxia, ophthalmoplegia) by interfering with **thiamine (Vitamin B1) metabolism**, particularly in malnourished individuals or those with increased metabolic demand like miliary tuberculosis. - The characteristic MRI findings of bilateral symmetrical lesions in the **mamillary bodies** and **thalamus**, along with **elevated serum lactate**, are hallmarks of severe thiamine deficiency, as thiamine is a critical cofactor in carbohydrate metabolism (e.g., pyruvate dehydrogenase). *Rifampicin* - Primarily associated with **hepatotoxicity** (though ALT elevation here is mild) and **orange discoloration of body fluids**. - It is a potent **CYP450 inducer** but does not typically cause acute neurological syndromes like Wernicke's encephalopathy or interfere with thiamine metabolism. *Pyrazinamide* - Common side effects include **hepatotoxicity** (often dose-related) and **hyperuricemia**, which can precipitate gout. - It does not cause central nervous system lesions, ophthalmoplegia, or interfere with thiamine pathways leading to lactic acidosis. *Ethambutol* - The most significant adverse effect is **optic neuritis**, leading to decreased visual acuity and **red-green color blindness**. - It does not present with confusion, ataxia, or the specific MRI findings observed in this patient's brain. *Streptomycin* - As an aminoglycoside, its primary toxicities include **ototoxicity** (vestibular and auditory damage) and **nephrotoxicity**. - It is not implicated in causing metabolic encephalopathy, thiamine deficiency, or the specific neurological symptoms and MRI findings seen in Wernicke's encephalopathy.

Q: A 3-month-old infant is brought to the emergency department with fever of 38.8°C, irritability, poor feeding, and a bulging fontanelle. Blood tests show: WBC 18.5 × 10⁹/L (neutrophils 15.2 × 10⁹/L), CRP 145 mg/L. Lumbar puncture reveals CSF white cells 1200/mm³ (85% neutrophils), protein 1.8 g/L, glucose 1.5 mmol/L (plasma glucose 4.8 mmol/L). Gram stain shows Gram-positive cocci in chains. What is the most appropriate antibiotic regimen?

Intravenous cefotaxime and amoxicillin. ***Intravenous cefotaxime and amoxicillin*** - In infants under 3 months, **cefotaxime** is preferred over ceftriaxone because it does not displace bilirubin from albumin, avoiding the risk of **kernicterus**. - **Amoxicillin** must be added to the regimen to provide specific coverage for **Listeria monocytogenes**, an organism not covered by third-generation cephalosporins. *Intravenous ceftriaxone alone* - **Ceftriaxone** is generally avoided in neonates and very young infants due to its potential to cause **biliary sludging** and hyperbilirubinemia, leading to **kernicterus**. - This regimen lacks coverage for **Listeria monocytogenes**, which is a significant pathogen causing meningitis in infants under 3 months of age. *Intravenous benzylpenicillin alone* - While **benzylpenicillin** provides coverage for common Gram-positive cocci (like Group B Streptococcus), it lacks the necessary broad-spectrum coverage for important Gram-negative pathogens such as **E. coli**. - Given the high mortality of neonatal meningitis, **empiric therapy** must cover a wide range of common bacterial pathogens, which this single antibiotic does not achieve. *Intravenous ceftriaxone and vancomycin* - This regimen includes **ceftriaxone**, which is contraindicated in infants under 3 months due to the risk of **kernicterus**. - Although **vancomycin** covers resistant Gram-positives, this combination still does not provide adequate coverage for **Listeria monocytogenes**, a crucial pathogen in this age group. *Intravenous cefotaxime and gentamicin* - While **cefotaxime** is appropriate, **gentamicin** (an aminoglycoside) has poor penetration into the **cerebrospinal fluid (CSF)**, making it less effective for treating meningitis. - This combination also does not adequately cover **Listeria monocytogenes**, for which amoxicillin is specifically indicated in infants.

Question 1

A 40-year-old woman with rheumatoid arthritis treated with methotrexate and infliximab undergoes screening for latent tuberculosis before starting therapy. Her Mantoux test shows 8 mm induration, and interferon-gamma release assay (IGRA) is positive. Chest X-ray is normal. She has no symptoms of active TB. What is the most appropriate management?

Accepted Answer

Commence isoniazid for 6 months before starting anti-TNF therapy

Answer

Start anti-TNF therapy immediately as the chest X-ray is normal

Answer

Commence full four-drug anti-tuberculous therapy for 6 months before starting anti-TNF therapy

Answer

Repeat the Mantoux test in 4 weeks to confirm the result

Answer

Perform a CT chest and bronchoscopy before making any treatment decisions

Question 2

A 5-year-old girl is brought to the emergency department with a 4-hour history of high fever, drowsiness, and a non-blanching purpuric rash on her legs and trunk. She is tachycardic with a capillary refill time of 4 seconds. Blood pressure is 85/50 mmHg. Blood cultures are taken and she is given immediate intravenous ceftriaxone. Which statutory notification requirement applies in this case?

Accepted Answer

Notification to the local Proper Officer must be made upon clinical suspicion, without waiting for laboratory confirmation

Answer

Notification to the UK Health Security Agency must be made within 3 working days of clinical diagnosis

Answer

Notification is only required once laboratory confirmation of Neisseria meningitidis is obtained

Answer

Notification should be made to the General Medical Council within 24 hours

Answer

Notification is the responsibility of the microbiologist once blood culture results are available

Question 3

A 35-year-old asylum seeker from Eritrea presents with a 2-month history of cough, weight loss, and fever. Chest X-ray shows bilateral upper lobe cavitation. Sputum microscopy reveals acid-fast bacilli. He has no known drug allergies and HIV test is negative. What is the most appropriate initial treatment regimen for this patient?

Accepted Answer

Rifampicin, isoniazid, pyrazinamide, and ethambutol for 2 months, followed by rifampicin and isoniazid for 4 months

Answer

Rifampicin, isoniazid, and pyrazinamide for 6 months

Answer

Rifampicin and isoniazid for 9 months

Answer

Rifampicin, isoniazid, pyrazinamide, ethambutol, and streptomycin for 2 months, followed by rifampicin, isoniazid, and ethambutol for 10 months

Answer

Moxifloxacin, isoniazid, pyrazinamide, and ethambutol for 6 months

Question 4

A 52-year-old man from Pakistan with newly diagnosed smear-positive pulmonary tuberculosis requires treatment. He has HIV coinfection (CD4 200 cells/mm³) and is taking tenofovir/emtricitabine/efavirenz. He also has chronic hepatitis B, hypertension (amlodipine 5mg daily), and epilepsy well-controlled on phenytoin 300mg daily. Initial ALT is 65 U/L, bilirubin 18 µmol/L. What is the most critical drug interaction requiring immediate management modification?

Accepted Answer

Rifampicin will reduce phenytoin levels significantly increasing seizure risk

Answer

Rifampicin will reduce efavirenz levels requiring dose adjustment of antiretroviral therapy

Answer

Isoniazid and rifampicin together create high hepatotoxicity risk with pre-existing liver disease

Answer

Rifampicin will reduce amlodipine levels causing inadequate blood pressure control

Answer

Pyrazinamide will worsen hepatitis B liver disease requiring modified TB regimen

Question 5

A 60-year-old man presents with progressive confusion, fever, and left-sided weakness over 3 days. MRI brain shows asymmetrical temporal lobe changes with haemorrhagic features. Lumbar puncture reveals: opening pressure 18 cmH2O, CSF red blood cells 850/mm³, white cells 245/mm³ (75% lymphocytes), protein 0.9 g/L, glucose 3.8 mmol/L (plasma glucose 5.5 mmol/L). CSF PCR for herpes simplex virus is positive. Despite intravenous aciclovir for 5 days, he remains confused with worsening seizures. What is the most appropriate next management step?

Accepted Answer

Add foscarnet to the treatment regimen due to possible aciclovir resistance

Answer

Continue aciclovir for full 14-day course as initial improvement takes time

Answer

Switch from intravenous aciclovir to oral valaciclovir for better CNS penetration

Answer

Stop aciclovir and start ganciclovir for possible CMV encephalitis

Answer

Increase the dose of aciclovir to 15 mg/kg three times daily

Question 6

A 29-year-old woman completes 6 months of treatment for drug-sensitive pulmonary tuberculosis with documented sputum culture conversion at 2 months. She is now asymptomatic with a normal chest X-ray. She wishes to conceive. She asks about the risk of TB recurrence during pregnancy and the safety of becoming pregnant. What is the most appropriate counselling regarding her conception plans?

Accepted Answer

She can conceive immediately as treatment is complete and risk of relapse is low

Answer

She should wait 12 months after treatment completion before conceiving due to high risk of relapse

Answer

She should wait 6 months after treatment completion and undergo repeat sputum cultures before conceiving

Answer

She should avoid pregnancy indefinitely due to risk of reactivation during immunosuppression of pregnancy

Answer

She should wait 24 months after treatment completion to ensure no late relapse

Question 7

A 45-year-old woman with miliary tuberculosis is started on standard four-drug therapy. After 3 weeks of treatment, she develops confusion, ataxia, and ophthalmoplegia. Her serum sodium is 128 mmol/L, ALT is 45 U/L (baseline 35 U/L), and serum lactate is 4.2 mmol/L. Brain MRI shows bilateral symmetrical lesions in the mamillary bodies and thalamus. Which anti-tuberculous drug is most likely responsible for this presentation?

Accepted Answer

Isoniazid

Answer

Rifampicin

Answer

Pyrazinamide

Answer

Ethambutol

Answer

Streptomycin

Question 8

A 72-year-old man develops acute bacterial meningitis and is treated with intravenous ceftriaxone and dexamethasone. Blood cultures grow Streptococcus pneumoniae with penicillin MIC of 2 mg/L. His clinical condition improves over 48 hours. CSF culture at 48 hours shows continued growth of the organism. What is the most appropriate modification to his antibiotic regimen?

Accepted Answer

Add vancomycin to the current regimen

Answer

Continue current regimen as clinical improvement suggests adequate treatment

Answer

Switch from ceftriaxone to high-dose benzylpenicillin

Answer

Add rifampicin to the current regimen

Answer

Stop dexamethasone and increase ceftriaxone dose

Question 9

A 38-year-old man with newly diagnosed HIV (CD4 count 120 cells/mm³) presents with fever, cough, and weight loss. Chest X-ray shows bilateral upper lobe infiltrates with cavitation. Three sputum samples are AFB smear-positive, and culture confirms Mycobacterium tuberculosis fully sensitive to first-line drugs. He is started on standard TB treatment. When should antiretroviral therapy (ART) be initiated?

Accepted Answer

After 2 weeks of TB treatment

Answer

Immediately, concurrent with TB treatment

Answer

After 2 months of TB treatment when the intensive phase is complete

Answer

After 6 months when TB treatment is complete

Answer

ART should be deferred until CD4 count falls below 100 cells/mm³

Question 10

A 3-month-old infant is brought to the emergency department with fever of 38.8°C, irritability, poor feeding, and a bulging fontanelle. Blood tests show: WBC 18.5 × 10⁹/L (neutrophils 15.2 × 10⁹/L), CRP 145 mg/L. Lumbar puncture reveals CSF white cells 1200/mm³ (85% neutrophils), protein 1.8 g/L, glucose 1.5 mmol/L (plasma glucose 4.8 mmol/L). Gram stain shows Gram-positive cocci in chains. What is the most appropriate antibiotic regimen?

Accepted Answer

Intravenous cefotaxime and amoxicillin

Answer

Intravenous ceftriaxone alone

Answer

Intravenous benzylpenicillin alone

Answer

Intravenous ceftriaxone and vancomycin

Answer

Intravenous cefotaxime and gentamicin

Serious & Notifiable Infections — MCQs

Serious & Notifiable Infections — MCQs

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