Pneumonia – Hospital Acquired Pneumonia versus Community Acquired Pneumonia Pathogens

History: 40 year old man with 1 week history of productive cough and fevers. 

Right middle lobe pneumonia: Single frontal upright chest radiograph shows discrete ground glass opacity with consolidation in the right middle lobe 

Right middle lobe pneumonia: Left lateral chest radiograph in the same patient shows marked consolidation of the right middle lobe, anterior and superior to the right oblique fissure.

This is a classic case of lobar pneumonia, which is most commonly bacterial in origin.

Hospital acquired pneumonia is commonly caused by: Staphylococcus Aureus, anaerobes, and gram negative organisms.

Community acquired pneumonia is commonly caused by: Pneumococcus, mycoplasma, viruses, and not commonly legionella or klebsiella.

If the lung consolidation doesn’t improve in 6-8 weeks, the concern is heightened for an obstructing lesion in the bronchus, such as bronchioalveolar cell carcinoma.

Read about the differential diagnosis for lung masses.

Read about the differential diagnosis for a solitary pulmonary nodule.