What are the main pathogens that cause pneumonia?

What are the main pathogens that cause pneumonia?

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 your patient needs to be hospitalized for pneumonia?