MI7.1-5 | Respiratory Tract Infections — Graded Quiz

A 65-year-old retired farmer from Rajasthan presents with 5 days of productive cough, fever 39°C, and dyspnoea. Pulse 110/min, RR 28/min, BUN 24 mg/dL, SpO2 88%. His chest X-ray shows right lower lobe consolidation. Using CURB-65, how many points does this patient score, and what is the appropriate management?

A 28-year-old construction worker is admitted with high-grade fever, dry cough, and myalgia after returning from a conference at a luxury hotel in Pune. His urine is sent for Legionella antigen testing, which returns positive. Which statement best explains why urinary antigen testing is the preferred rapid diagnostic tool for this infection?

A 4-month-old infant in a government hospital NICU develops worsening tachypnoea and hypoxia. On auscultation, fine bilateral crackles are heard. Nasopharyngeal aspirate is sent for direct fluorescent antibody (DFA) testing, which is positive for a paramyxovirus. Which of the following statements about this pathogen is most accurate?

A 55-year-old patient with COPD develops fever and purulent sputum 10 days after ventilation for an exacerbation in the MICU. His tracheal aspirate Gram stain shows Gram-negative rods. Which empirical antibiotic regimen is most appropriate for ventilator-associated pneumonia (VAP) in this setting?

A 7-year-old unvaccinated child presents with a paroxysmal cough that ends in an inspiratory whoop followed by post-tussive vomiting. Blood count shows lymphocyte count of 18,000/µL. Culture on Bordet-Gengou agar grows small, smooth, glistening colonies with a surrounding zone of haemolysis. Which virulence mechanism of this pathogen directly inhibits phagocyte function?

An immunocompetent 40-year-old archaeologist who recently returned from excavating a site in Maharashtra develops fever, weight loss, and bilateral hilar lymphadenopathy with multiple pulmonary nodules on CT. Bronchoalveolar lavage cytology shows small, oval yeast cells within macrophages (2–4 µm). Which organism is most likely, and what is the definitive treatment for disseminated disease?

A 32-year-old HIV-positive patient (CD4 count 80/µL) from Mumbai has a chest X-ray showing a thick-walled cavity in the right upper lobe. A high-resolution CT shows a round, dense opacity within the cavity with a crescent of air around it ('air crescent sign'). He is not currently on any antifungal therapy. What is the most likely diagnosis and the pathological mechanism of cavity formation?

A nurse in a Delhi tuberculosis ward has a BCG vaccination scar and a positive Mantoux test (18 mm induration). She has no symptoms and a normal chest X-ray. She undergoes QuantiFERON-TB Gold In-Tube (IGRA) testing, which is positive. How should this discordance be interpreted?

A 45-year-old man with pulmonary tuberculosis on second month of HRZE therapy (Category I NTEP regimen) has a sputum smear that remains positive. A drug sensitivity test returns: resistant to Isoniazid and Rifampicin, sensitive to fluoroquinolones and injectables. What category of TB does he have, and what regimen change is appropriate?

A 70-year-old man with poor dentition is found unconscious after a seizure at home and is brought to the casualty. He is intubated. A chest X-ray taken 48 hours later shows consolidation in the right lower lobe (posterior segment). Blood cultures are negative. Sputum culture grows a polymicrobial mixture including Fusobacterium nucleatum and Prevotella melaninogenica. What is the most appropriate first-line antibiotic for this condition?

A 72-year-old male ex-miner on long-term prednisolone for COPD presents with fever, haemoptysis, and rapidly progressive bilateral pulmonary infiltrates. Bronchoalveolar lavage reveals septate hyphae with 45° acute-angle dichotomous branching. What is the pathogenesis underlying the high mortality in this condition?

During a microbiology practical, a student processes a sputum sample from a suspected CAP patient. After Gram staining, she observes lancet-shaped Gram-positive diplococci surrounded by clear zones (capsule not staining). She inoculates the sample on Blood Agar + 5% CO2 and Optochin discs are placed. Next morning, she notices alpha-haemolysis with a zone of inhibition around the Optochin disc. Which confirmatory test is next, and what does a bile solubility test result of 'complete lysis' indicate?