The commonest organism causing Empyema in a child under 2 years –
**Core Concept**
Empyema, a complication of pneumonia, is a collection of pus in the pleural space. In children under 2 years, the causative organism is often related to the common pathogens causing respiratory infections in this age group.
**Why the Correct Answer is Right**
The most common organism causing empyema in a child under 2 years is Staphylococcus aureus. This bacterium is a frequent cause of respiratory infections in young children, and its presence in the pleural space can lead to empyema. S. aureus produces enzymes like coagulase that contribute to its virulence and ability to cause disease.
**Why Each Wrong Option is Incorrect**
* **Option A:** Streptococcus pneumoniae is a common cause of pneumonia in children, but it is less frequently associated with empyema compared to S. aureus.
* **Option B:** Haemophilus influenzae type b (Hib) is a cause of pneumonia and meningitis in young children, but it is not typically associated with empyema.
* **Option D:** Klebsiella pneumoniae is a cause of pneumonia in children, but it is more commonly seen in older children and adults.
**Clinical Pearl / High-Yield Fact**
In children under 2 years, empyema is often a complication of Staphylococcus aureus pneumonia, and it may present with signs of respiratory distress, fever, and decreased breath sounds.
**Correct Answer: C. Staphylococcus aureus.**