The causative agent of pneumonia acquired by inhalation from air-conditioners is which organism?

The causative agent of pneumonia acquired by inhalation from air-conditioners is which organism?

• A. Chlamydia pneumoniae
• B. Pneumocystis carinii
• C. Legionella pneumophila
• D. Salmonella typhi

Answer: (C)

Pneumonia acquired from inhaling aerosols produced by air-conditioning systems is classically caused by Legionella pneumophila. This organism thrives in water systems—cooling towers, hot water tanks, humidifiers—and spreads when aerosolized droplets are inhaled. Transmission isn’t typically person-to-person, which helps distinguish it from other pneumonias. Chlamydia pneumoniae can cause atypical pneumonia but is usually spread between people and isn’t tied to AC-related aerosols. Pneumocystis carinii (jirovecii) pneumonia occurs mainly in immunocompromised individuals, not specifically from air-conditioning aerosols. Salmonella typhi causes typhoid fever and is transmitted via contaminated food or water, not through inhaled aerosols from AC systems.

Pneumonia acquired from inhaling aerosols produced by air-conditioning systems is classically caused by Legionella pneumophila. This organism thrives in water systems—cooling towers, hot water tanks, humidifiers—and spreads when aerosolized droplets are inhaled. Transmission isn’t typically person-to-person, which helps distinguish it from other pneumonias. Chlamydia pneumoniae can cause atypical pneumonia but is usually spread between people and isn’t tied to AC-related aerosols. Pneumocystis carinii (jirovecii) pneumonia occurs mainly in immunocompromised individuals, not specifically from air-conditioning aerosols. Salmonella typhi causes typhoid fever and is transmitted via contaminated food or water, not through inhaled aerosols from AC systems.