Serious & Notifiable Infections Practice Questions

Q: A 19-year-old student presents with sudden onset headache, fever, vomiting, and drowsiness. On examination, she has neck stiffness and Kernig's sign is positive. Lumbar puncture shows: opening pressure 28 cmH2O, cloudy CSF, white cells 2400/mm³ (95% neutrophils), protein 3.2 g/L, glucose 1.8 mmol/L (plasma glucose 6.5 mmol/L). Gram stain shows Gram-negative diplococci. Which organism is most likely responsible?

Neisseria meningitidis. ***Neisseria meningitidis***- The presence of **Gram-negative diplococci** on the CSF Gram stain is the classic and most definitive finding for *Neisseria meningitidis*.- The clinical presentation of sudden onset fever, headache, meningeal signs (neck stiffness, Kernig's) in a **young adult** (19-year-old student), coupled with the CSF profile (elevated opening pressure, cloudy, high protein, low glucose, and marked **neutrophilic pleocytosis**), is highly characteristic of bacterial meningitis caused by this organism.*Escherichia coli*- *Escherichia coli* are **Gram-negative bacilli (rods)**, which would appear as rod-shaped bacteria on Gram stain, not diplococci.- While a cause of bacterial meningitis, *E. coli* is predominantly seen in **neonates** or immunocompromised individuals, making it less likely in a healthy 19-year-old.*Streptococcus pneumoniae*- *Streptococcus pneumoniae* is a major cause of bacterial meningitis but is characterized by **Gram-positive diplococci**, staining purple, not Gram-negative.- This organism is more commonly associated with very young children, older adults, or individuals with specific risk factors like **splenic dysfunction**.*Haemophilus influenzae type b*- *Haemophilus influenzae type b* (Hib) appears as **Gram-negative coccobacilli**, which are smaller, more pleomorphic, and often less distinctly diplococcal than *Neisseria*.- The incidence of Hib meningitis has been significantly reduced in many populations due to widespread **childhood vaccination programs**.*Listeria monocytogenes*- *Listeria monocytogenes* are characterized as **Gram-positive rods**, directly contradicting the Gram-negative finding on the CSF Gram stain.- It typically affects specific vulnerable populations, including **neonates**, pregnant women, the **elderly**, and **immunocompromised** individuals.

Q: A 32-year-old man with HIV (CD4 count 85 cells/mm³) presents with headache, fever, and confusion over 5 days. CT head shows multiple ring-enhancing lesions with surrounding oedema. Lumbar puncture reveals: opening pressure 24 cmH2O, CSF protein 0.8 g/L, glucose 2.1 mmol/L (plasma glucose 5.2 mmol/L), white cells 45/mm³ (90% lymphocytes). India ink stain is positive. What is the most likely causative organism?

Cryptococcus neoformans. ***Cryptococcus neoformans*** - The positive **India ink stain** demonstrating encapsulated yeasts in the CSF is pathognomonic for **Cryptococcus neoformans** in this immunocompromised patient (CD4 count 85 cells/mm³). - The clinical picture of **meningitis** (headache, fever, confusion, elevated opening pressure, lymphocytic pleocytosis, low glucose) is characteristic, and **cryptococcomas** can explain the ring-enhancing lesions. *Toxoplasma gondii* - While **Toxoplasma gondii** is the most common cause of **multiple ring-enhancing lesions** in HIV, it would not yield a positive **India ink stain** on CSF examination. - CSF parameters in toxoplasmosis are typically non-specific, lacking the distinct **fungal meningitis** profile (low glucose, lymphocytic pleocytosis) seen here. *Mycobacterium tuberculosis* - **Tuberculous meningitis** usually presents with more profoundly **low CSF glucose** and significantly **higher CSF protein** levels than seen in this case. - Diagnosis of TB meningitis relies on **Acid-Fast Bacilli (AFB)** staining, PCR, or culture for *Mycobacterium tuberculosis*, not an India ink stain. *JC virus* - **JC virus** causes **Progressive Multifocal Leukoencephalopathy (PML)**, which is characterized by **non-enhancing white matter lesions** on CT or MRI, not ring-enhancing lesions. - PML does not typically cause the meningitic syndrome or the inflammatory CSF changes, such as elevated white cells and protein, seen in this patient. *Listeria monocytogenes* - **Listeria monocytogenes** causes bacterial meningitis, typically presenting with a **neutrophilic pleocytosis** in the CSF, unlike the lymphocytic predominance here. - Being a bacterium, it would not be detected by an **India ink stain**, and while it affects immunocompromised patients, the overall picture here points away from *Listeria*.

Question 1

A 42-year-old woman presents with a 4-week history of headache, low-grade fever, and personality changes. She is originally from India and moved to the UK 6 months ago. CT head shows basal meningeal enhancement and hydrocephalus. Lumbar puncture reveals: opening pressure 32 cmH2O, clear CSF, white cells 180/mm³ (80% lymphocytes), protein 2.5 g/L, glucose 1.9 mmol/L (plasma glucose 5.8 mmol/L). Ziehl-Neelsen stain is negative. What is the most appropriate initial management?

Accepted Answer

Start four-drug anti-tuberculous therapy immediately

Answer

Wait for mycobacterial culture results before starting treatment

Answer

Perform repeat lumbar puncture for larger CSF volume before starting treatment

Answer

Start empirical aciclovir for possible viral meningoencephalitis

Answer

Start empirical treatment for fungal meningitis with amphotericin B

Question 2

A 55-year-old man with type 2 diabetes is diagnosed with pulmonary tuberculosis. He has been on metformin 1g twice daily and gliclazide 80mg twice daily for glycaemic control. After starting standard four-drug anti-tuberculous therapy, his HbA1c increases from 58 mmol/mol to 76 mmol/mol over 4 weeks. What is the most likely explanation for this deterioration in glycaemic control?

Accepted Answer

Rifampicin-induced cytochrome P450 enzyme induction reducing gliclazide levels

Answer

Isoniazid-induced pancreatitis reducing insulin secretion

Answer

Pyrazinamide causing insulin resistance

Answer

Ethambutol interfering with metformin absorption

Answer

Poor adherence to diabetic medications due to pill burden

Question 3

A 19-year-old student presents with sudden onset headache, fever, vomiting, and drowsiness. On examination, she has neck stiffness and Kernig's sign is positive. Lumbar puncture shows: opening pressure 28 cmH2O, cloudy CSF, white cells 2400/mm³ (95% neutrophils), protein 3.2 g/L, glucose 1.8 mmol/L (plasma glucose 6.5 mmol/L). Gram stain shows Gram-negative diplococci. Which organism is most likely responsible?

Accepted Answer

Neisseria meningitidis

Answer

Escherichia coli

Answer

Streptococcus pneumoniae

Answer

Haemophilus influenzae type b

Answer

Listeria monocytogenes

Question 4

A 28-year-old healthcare worker has a positive Mantoux test (15 mm induration) during routine occupational health screening. She is asymptomatic with a normal chest X-ray. She received BCG vaccination as a teenager. Her interferon-gamma release assay (IGRA) is positive. What is the most appropriate next management step?

Accepted Answer

Offer treatment for latent tuberculosis infection with 3 months of rifampicin and isoniazid

Answer

No treatment required; likely due to previous BCG vaccination

Answer

Offer treatment for latent tuberculosis infection with 6 months of isoniazid

Answer

Repeat Mantoux test in 6 weeks to confirm result

Answer

Commence full anti-tuberculous therapy with four drugs for 6 months

Question 5

A 32-year-old man with HIV (CD4 count 85 cells/mm³) presents with headache, fever, and confusion over 5 days. CT head shows multiple ring-enhancing lesions with surrounding oedema. Lumbar puncture reveals: opening pressure 24 cmH2O, CSF protein 0.8 g/L, glucose 2.1 mmol/L (plasma glucose 5.2 mmol/L), white cells 45/mm³ (90% lymphocytes). India ink stain is positive. What is the most likely causative organism?

Accepted Answer

Cryptococcus neoformans

Answer

Toxoplasma gondii

Answer

Mycobacterium tuberculosis

Answer

JC virus

Answer

Listeria monocytogenes

Question 6

A 45-year-old woman from Somalia, who moved to the UK 2 years ago, is diagnosed with active pulmonary tuberculosis. She lives in a house with her husband, two children aged 8 and 12 years, and her elderly mother. What is the most appropriate contact screening strategy for her household members?

Accepted Answer

Mantoux test for all contacts, with chest X-ray if positive; repeat Mantoux at 6 weeks if initially negative

Answer

Mantoux test and chest X-ray for all contacts immediately

Answer

Interferon-gamma release assay (IGRA) for all contacts immediately with chest X-ray

Answer

Chest X-ray for all contacts with Mantoux test only if symptomatic

Answer

IGRA test for adults and Mantoux test for children, both with immediate chest X-ray

Question 7

A 24-year-old university student presents to the emergency department with a 6-hour history of severe headache, photophobia, neck stiffness, and fever of 39.2°C. On examination, she has a non-blanching purpuric rash on her lower limbs. Blood pressure is 95/60 mmHg and heart rate is 115 bpm. What is the most appropriate immediate management before lumbar puncture?

Accepted Answer

Administer intravenous ceftriaxone immediately

Answer

Perform CT head scan first

Answer

Administer intravenous dexamethasone first

Answer

Obtain blood cultures before any antibiotic administration

Answer

Administer intravenous benzylpenicillin and await lumbar puncture results

Question 8

A 68-year-old man presents with a 3-week history of productive cough, night sweats, and unintentional weight loss of 5 kg. He is a former smoker with a 40 pack-year history. Chest X-ray shows upper lobe cavitation. Sputum smear microscopy reveals acid-fast bacilli. What is the most appropriate initial treatment regimen for this patient?

Accepted Answer

Rifampicin, isoniazid, pyrazinamide, and ethambutol for 2 months, then rifampicin and isoniazid for 4 months

Answer

Rifampicin and isoniazid for 6 months

Answer

Rifampicin, isoniazid, and pyrazinamide for 6 months

Answer

Rifampicin, isoniazid, pyrazinamide, and ethambutol for 6 months

Answer

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

Serious & Notifiable Infections — MCQs

Serious & Notifiable Infections — MCQs

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