“Pneumonia Alba” is caused by:
**Core Concept**
Pneumonia Alba, also known as primary lobar pneumonia, is a type of bacterial pneumonia characterized by a dense consolidation of the lung parenchyma due to an inflammatory response. The condition is typically caused by a specific pathogen that invades the lung tissue, leading to an intense inflammatory reaction.
**Why the Correct Answer is Right**
The correct answer is **Streptococcus pneumoniae**. This bacterium is a Gram-positive coccus that is commonly found in the upper respiratory tract. It can invade the lung tissue, causing an intense inflammatory response and leading to the characteristic consolidation seen in Pneumonia Alba. **S. pneumoniae** produces a polysaccharide capsule that helps it evade the host's immune system, allowing it to cause disease.
**Why Each Wrong Option is Incorrect**
**Option A:** Haemophilus influenzae is a Gram-negative coccus that can cause pneumonia, but it is not typically associated with Pneumonia Alba. H. influenzae is more commonly linked to secondary bacterial pneumonia.
**Option B:** Klebsiella pneumoniae is a Gram-negative rod that can cause pneumonia, but it is not the primary cause of Pneumonia Alba. K. pneumoniae is more commonly seen in patients with underlying chronic diseases or alcoholism.
**Option C:** Pneumocystis jirovecii is a fungus that can cause pneumonia in immunocompromised patients, but it is not associated with Pneumonia Alba. P. jirovecii pneumonia is more commonly seen in patients with HIV/AIDS.
**Clinical Pearl / High-Yield Fact**
Pneumonia Alba is often associated with a high fever, chills, and a productive cough that may produce rust-colored sputum. The condition can be diagnosed with chest X-rays, which typically show lobar consolidation.
**Correct Answer:** C. Streptococcus pneumoniae.