What are the main pathogens that cause pneumonia? How would the treatment for pn

What are the main pathogens that cause pneumonia? How would the treatment for pneumonia in a 23 year-old otherwise healthy patient possibly differ from a 66 year-old diabetic COPD patient. Would you order the same antibiotics for both patients? How would you determine if a your patient needs to be hospitalized for pneumonia?
Expectations
Initial Post:
Length: A minimum of 250 words, not including references
Citations: At least one high-level scholarly reference in APA from within the last 5 years