A middle-aged man with pneumonia, exposure to misted greens, and immunosuppression is most likely infected with which organism?

A middle-aged man with pneumonia, exposure to misted greens, and immunosuppression is most likely infected with which organism?

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

Answer: (A)

Exposure to aerosolized water containing a pathogen is a key clue. Legionella pneumophila thrives in man-made water systems and is classically acquired by inhaling contaminated aerosols from sources like humidifiers, cooling towers, fountains, or misted water. In immunocompromised individuals, this organism can cause a pneumonia that fits the scenario of exposure to misted greens, making Legionella the most likely culprit. The other organisms don’t fit as well with the exposure. Bordetella pertussis causes pertussis, marked by a paroxysmal cough and is spread by droplets rather than inhaled water aerosols. Klebsiella pneumoniae typically causes severe pneumonia in people with risk factors like alcoholism or chronic lung disease and isn’t tied to aerosolized water exposure. Moraxella catarrhalis is more often associated with COPD-related infections or otitis media and also isn’t linked to water aerosol exposure. So the pneumonia in this immunosuppressed patient after inhaling misted water points most strongly to Legionella pneumophila.

Exposure to aerosolized water containing a pathogen is a key clue. Legionella pneumophila thrives in man-made water systems and is classically acquired by inhaling contaminated aerosols from sources like humidifiers, cooling towers, fountains, or misted water. In immunocompromised individuals, this organism can cause a pneumonia that fits the scenario of exposure to misted greens, making Legionella the most likely culprit.

The other organisms don’t fit as well with the exposure. Bordetella pertussis causes pertussis, marked by a paroxysmal cough and is spread by droplets rather than inhaled water aerosols. Klebsiella pneumoniae typically causes severe pneumonia in people with risk factors like alcoholism or chronic lung disease and isn’t tied to aerosolized water exposure. Moraxella catarrhalis is more often associated with COPD-related infections or otitis media and also isn’t linked to water aerosol exposure.

So the pneumonia in this immunosuppressed patient after inhaling misted water points most strongly to Legionella pneumophila.