Certified Pediatric Nurse (CPN)

In a child diagnosed with croup, which organism is most likely responsible for the infection?

1. Streptococcus pneumoniae

2. Influenza A and B

3. Staphylococcus aureus

4. Haemophilus influenzae

The correct answer is: Influenza A and B

Croup, also known as laryngotracheobronchitis, is primarily caused by viral infections, with the most common culprits being the parainfluenza virus and respiratory syncytial virus (RSV). However, among the options presented, Influenza A and B viruses are notably associated with croup. These viruses can lead to inflammation and swelling of the upper airway, producing the characteristic cough and stridor observed in croup. While other organisms listed can cause respiratory infections, they are not typically the main pathogens behind croup. For example, Streptococcus pneumoniae and Staphylococcus aureus are more commonly associated with bacterial pneumonia or other types of bacterial infections rather than the viral pathogenesis involved in croup. Haemophilus influenzae is associated with serious bacterial infections, notably epiglottitis, which presents differently than croup. Therefore, Influenza A and B viruses are recognized as significant contributors to the croup syndrome, making them the organisms most likely responsible in this scenario.