Streptococcus pneumoniae is diagnosed by which two methods?

• A. Sputum and blood cultures
• B. Urine antigen and serology
• C. Sputum Gram stain and chest X-ray
• D. Blood culture and pleural fluid analysis

Answer: (A)

Diagnosis relies on directly identifying Streptococcus pneumoniae from clinical specimens. The most straightforward way is to isolate the organism in culture from respiratory material to diagnose pneumonia, with sputum culture commonly used for that purpose. Blood cultures are important because they detect pneumococcemia, confirming invasive disease when present. While urinary antigen testing can rapidly indicate infection and imaging like chest X-ray shows pneumonia, they don’t provide the organism’s identity as reliably as culture does. When both respiratory infection and possible bacteremia are being evaluated, sputum culture and blood culture together offer the clearest confirmation.