Which statement accurately differentiates pneumonia etiologies (viral, bacterial, and atypical) in terms of common pathogens and antibiotic use?

• A. Viral pneumonia is caused by influenza and RSV and antibiotics are routinely indicated.
• B. Atypical pneumonia is caused by Mycoplasma and Chlamydophila and never requires antibiotics.
• C. Bacterial pneumonia is commonly caused by Streptococcus pneumoniae and Staphylococcus aureus, and antibiotics are indicated.
• D. Atypical pneumonia is caused by viruses and always requires macrolide therapy.

Answer: (C)

Understanding how pneumonia pathogens differ by etiology helps explain why antibiotic use varies. Bacterial pneumonia is most often caused by Streptococcus pneumoniae, with Staphylococcus aureus (including MRSA) also seen, and antibiotics are the standard treatment to target these bacteria.

Viral pneumonia, caused by pathogens such as influenza viruses and respiratory syncytial virus, generally does not require antibiotics because there is no bacterial infection to treat; management is usually supportive, though antiviral therapy may be appropriate for influenza and antibiotics may be added only if a bacterial coinfection is suspected.

Atypical pneumonia involves organisms like Mycoplasma pneumoniae and Chlamydophila pneumoniae. These are bacteria, but they behave differently from the classic extracellular bacteria, so they’re typically treated with antibiotics that cover atypical pathogens (for example macrolides or doxycycline, sometimes fluoroquinolones).

The statement that bacterial pneumonia is commonly caused by Streptococcus pneumoniae and Staphylococcus aureus, and antibiotics are indicated, best captures the clear distinction in common pathogens and the need for antibiotic therapy. The other options either misidentify the typical pathogens for viral or atypical etiologies or incorrectly state the role of antibiotics.