Pneumonia and other Lower Respiratory Tract Infections Quiz

See Lung Abscesses. Option B is correct because Streptococcus pneumoniae (also called the pneumococcus) is the most common bacterial cause of community-acquired pneumonia worldwide. Community-acquired pneumonia means pneumonia that starts outside hospital. Streptococcus pneumoniae is a gram-positive coccus (a round bacterium that stains purple with the Gram stain) that usually lives harmlessly in the nose and throat and can spread down into the lungs, where it triggers inflammation in the alveoli, the air sacs. The air sacs fill with fluid and inflammatory cells, a process called consolidation, which gives the classic signs of fever, productive cough, pleuritic chest pain and dull percussion with bronchial breathing. Other important causes include Haemophilus influenzae, atypical bacteria such as Mycoplasma and Legionella, and respiratory viruses. A useful way to remember it is that the commonest community pneumonia has a common bug, the pneumococcus.

• Organism: Streptococcus pneumoniae, a gram-positive coccus, is the most common bacterial cause of community-acquired pneumonia worldwide.
• Setting: community-acquired pneumonia means pneumonia that starts outside hospital.
• Consolidation: the air sacs fill with fluid and inflammatory cells, giving fever, productive cough, pleuritic chest pain and dull percussion with bronchial breathing.

The setting in which pneumonia is acquired therefore guides the likely organism: think of the pneumococcus first for a typical community illness, and of hospital organisms such as Staphylococcus aureus and Pseudomonas when the pneumonia starts after at least 48 hours in hospital.