The following is the paraphrased version of question 125, with five options and a correct answer explanation.
---
**Specialty: Infectious Disease**
**Question 125)**
A 60-year-old woman presents with fever, cough, and pleuritic chest pain. She has a history of chronic obstructive pulmonary disease (COPD). Her chest X-ray shows a right lower lobe consolidation. Blood cultures and sputum samples are taken. What is the most likely causative organism for her condition?
A) Streptococcus pneumoniae
B) Staphylococcus aureus
C) Mycobacterium tuberculosis
D) Haemophilus influenzae
E) Pseudomonas aeruginosa
**Correct Answer:** A) Streptococcus pneumoniae
**Explanation:** Streptococcus pneumoniae is the most common cause of community-acquired pneumonia (CAP), especially in patients with underlying conditions such as COPD. Although Haemophilus influenzae is also a common pathogen in COPD patients, Streptococcus pneumoniae remains the most frequent cause of lobar pneumonia across different patient populations. The choice of Streptococcus pneumoniae is supported by the clinical presentation and radiologic findings typical of pneumococcal pneumonia.