Which pneumonia is classically associated with late summer and presents with high fever and bradycardia?

• A. Pneumococcal pneumonia
• B. Mycoplasma pneumoniae
• C. Chlamydia pneumoniae
• D. Legionella pneumophila

Answer: (D)

Legionella pneumonia is defined by a distinctive combination: high fever with relative bradycardia (the heart rate is lower than expected for the degree of fever, a phenomenon sometimes called a Faget sign) and an exposure pattern tied to aerosolized water sources. It tends to show up in outbreaks during late summer when people are more likely to encounter cooling towers, hot tubs, fountains, and other contaminated water systems. The organism is a Gram-negative rod that grows in warm water and isn’t spread person-to-person; diagnosis is often made by a urinary antigen test or culture on specialized media. Treatment relies on a macrolide or a fluoroquinolone.

This scenario fits Legionella best because the high fever paired with bradycardia is atypical for most other pneumonias, which usually present with tachycardia. Other causes like pneumococcal pneumonia, mycoplasma, or Chlamydia pneumoniae tend to lack this bradycardic response and aren’t typically linked to summer-time water-system exposure.