What is the most common cause of community-acquired pneumonia in adults?

Streptococcus pneumoniae is the most common cause of community-acquired pneumonia in adults. This bacterium is encapsulated, gram-positive, and is particularly adept at evading the immune system, which makes it a frequent culprit in respiratory infections. The prevalence of Streptococcus pneumoniae in community-acquired pneumonia is well-documented in clinical guidelines and studies, attributing to it a significant percentage of cases seen in outpatient settings and among hospitalized patients.

Moreover, the virulence factors of Streptococcus pneumoniae, such as its polysaccharide capsule, contribute to its ability to cause disease and facilitate infection by adhering to respiratory epithelial cells and avoiding phagocytosis. As a result, clinicians often initiate empirical antibiotic therapy targeting this pathogen when diagnosing community-acquired pneumonia in adults, especially in populations at risk, such as the elderly or those with underlying health conditions.