A 62-year-old man with COPD presents with acute onset fever (39.2°C), productive cough with purulent sputum, and dyspnea for 3 days. Chest X-ray shows patchy infiltrates in the right lower and middle lobes with a bronchial distribution. Which investigation is most appropriate to confirm the diagnosis and guide antimicrobial therapy?
A. High-resolution CT chest with contrast
B. Serum procalcitonin level
C. Sputum culture and Gram stain
D. Bronchoscopic alveolar lavage
Explanation
Investigation of Choice in Bronchopneumonia
Key Point
Sputum culture and Gram stain is the gold standard for microbiological diagnosis and antibiotic susceptibility testing in bronchopneumonia.
Rapid progression in patients with underlying lung disease (COPD)
Sputum examination provides:
1.
Direct identification of causative organism (Gram stain morphology)
2.
Culture for definitive organism isolation
3.
Antimicrobial susceptibility for targeted therapy
4.
Non-invasive collection method
Diagnostic Approach in Pneumonia
Table
Investigation
Indication
Yield
Invasiveness
Sputum culture & Gram stain
Outpatient/ward bronchopneumonia
High (>80%)
Non-invasive
Blood culture
Sepsis, bacteremia risk
Moderate (10–20%)
Minimally invasive
HRCT chest
Atypical presentation, complications
High (anatomical detail)
Non-invasive, imaging
BAL (bronchoscopy)
Immunocompromised, no sputum
High
Invasive
Serum procalcitonin
Prognostication, severity
Moderate
Non-invasive
Clinical Pearl
In community-acquired bronchopneumonia with productive cough, a good-quality sputum sample (>25 WBCs, <10 epithelial cells per low-power field) is diagnostic and cost-effective.
High-YieldNEET PG
Bronchopneumonia in COPD patients is commonly caused by Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis — organisms that grow readily on routine culture media.
Why Other Investigations Are Secondary
HRCT: Provides anatomical detail but does NOT identify organism; reserved for complications or atypical cases
BAL: Invasive; reserved for immunocompromised patients or when sputum cannot be obtained
Procalcitonin: Prognostic marker, not diagnostic; does not guide organism-specific therapy
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