Lobar pneumonia is primarily caused by which bacterium?

Lobar pneumonia is primarily caused by Streptococcus pneumoniae, a Gram-positive bacterium that is a common pathogen in community-acquired pneumonia. This organism typically leads to a significant inflammatory response in the alveoli, resulting in consolidation of lung tissue, which is characteristic of lobar pneumonia. The infection often presents with symptoms such as high fever, chills, cough, and pleuritic chest pain.

Streptococcus pneumoniae is particularly notorious for affecting healthy individuals and can cause severe respiratory illness. The ability of this bacterium to form a thick capsule makes it virulent, as it helps evade the host's immune response. The inflammatory process it induces causes fluid and pus to fill the alveolar spaces, leading to the classical presentation on chest imaging and clinical findings associated with lobar pneumonia.

Other pathogens listed have different associations with pneumonia types. For example, Staphylococcus aureus is usually linked with post-viral pneumonia or lung infections in individuals with comorbidities. Escherichia coli is more commonly associated with aspiration pneumonia and not typically with lobar pneumonia. Mycoplasma pneumoniae is known for causing atypical pneumonia, which often has a different clinical course and presentation than lobar pneumonia caused by Streptococcus pneumoniae