A middle-aged man with a history of smoking and heavy alcohol use develops atypical pneumonia. He works in the produce section where greens are misted. Which organism is the most likely etiologic agent?

A middle-aged man with a history of smoking and heavy alcohol use develops atypical pneumonia. He works in the produce section where greens are misted. Which organism is the most likely etiologic agent?

• A. Moraxella catarrhalis
• B. Legionella pneumophila
• C. Bordetella pertussis
• D. Klebsiella pneumoniae

Answer: (C)

Legionella pneumophila fits best because it’s a classic cause of pneumonia linked to inhaling aerosolized water from environmental sources, such as misting systems in produce departments. Legionella thrives in water systems and is acquired when someone breathes in contaminated droplets, which matches the scenario of greens being misted in a store. The patient’s age and smoking history also raise the risk for atypical pneumonias like Legionella. Bordetella pertussis, by contrast, causes pertussis (whooping cough) and is transmitted mainly through respiratory droplets between people; it features a prolonged paroxysmal cough rather than the atypical pneumonia pattern associated with Legionella. The other organisms listed are less consistent with the setting and presentation: Moraxella catarrhalis tends to cause spread among people with COPD, Klebsiella pneumoniae is classically linked to severe lobar pneumonia in alcoholics, and neither is typically tied to environmental water aerosols in a workplace producing an atypical pneumonia.

Legionella pneumophila fits best because it’s a classic cause of pneumonia linked to inhaling aerosolized water from environmental sources, such as misting systems in produce departments. Legionella thrives in water systems and is acquired when someone breathes in contaminated droplets, which matches the scenario of greens being misted in a store. The patient’s age and smoking history also raise the risk for atypical pneumonias like Legionella.

Bordetella pertussis, by contrast, causes pertussis (whooping cough) and is transmitted mainly through respiratory droplets between people; it features a prolonged paroxysmal cough rather than the atypical pneumonia pattern associated with Legionella. The other organisms listed are less consistent with the setting and presentation: Moraxella catarrhalis tends to cause spread among people with COPD, Klebsiella pneumoniae is classically linked to severe lobar pneumonia in alcoholics, and neither is typically tied to environmental water aerosols in a workplace producing an atypical pneumonia.