What is the most common causative bacterial pathogen in community-acquired pneumonia (CAP) in immunocompetent adults?
Answer and explanation
Correct answer: A. Streptococcus pneumoniae
- Step 1: Community-acquired pneumonia (CAP) in immunocompetent adults can arise from multiple typical and atypical respiratory bacterial pathogens.
- Step 2: Across all adult age demographics worldwide, the Gram-positive lancet-shaped diplococcus Streptococcus pneumoniae (pneumococcus) is consistently the most common causative bacterial pathogen.
Answer
Streptococcus pneumoniae.
Why not the others: Pseudomonas aeruginosa is seen in cystic fibrosis and bronchiectasis, Staphylococcus aureus is common post-influenza or in IV drug users, and Klebsiella pneumoniae typically affects alcoholics and malnourished patients.
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