Which diagnostic test is used to identify the causative organism in pneumonia before starting antibiotic therapy?

• A. Sputum culture
• B. Chest x-ray only
• C. MRI
• D. ECG

Answer: (A)

The important concept here is identifying the exact pathogen causing pneumonia so antibiotics can be targeted rather than broad-spectrum. A sputum culture provides the specific organism and, with susceptibility testing, guides which antibiotic will be most effective. Collecting a good respiratory specimen before starting antibiotics maximizes the chance of growing the causative bacteria and obtaining meaningful results, which helps tailor therapy and improve outcomes.

Imaging tests like chest x-ray show that pneumonia is present and its extent but do not reveal the organism. MRI and ECG are not used to identify causative pathogens in pneumonia.