Outbreaks in ICUs associated with faucet aerators and humidifiers commonly involve which microorganism?

• A. Klebsiella pneumoniae
• B. Pseudomonas aeruginosa
• C. Salmonella spp.
• D. Serratia marcescens

Answer: (B)

Moist hospital environments, like faucet aerators and humidifiers, favor organisms that can persist in water systems and be dispersed to patients. Pseudomonas aeruginosa fits this pattern best because it loves damp places, readily colonizes plumbing and device surfaces, and forms resilient biofilms. In ICUs, it can contaminate taps, humidifiers, and respiratory equipment, and when humidifiers aerosolize contaminated water, vulnerable patients—especially those with impaired immunity or lung disease—are at higher risk for serious infections such as pneumonia or bacteremia. Its intrinsic resistance to many disinfectants makes these water-associated outbreaks particularly troublesome, helping explain why faucet aerators and humidifiers are classic sources.

While Klebsiella pneumoniae and Serratia marcescens can cause hospital infections and may appear in water-related contexts, they do not show the same strong association with faucet aerators and humidifiers as Pseudomonas aeruginosa. Salmonella is not typically linked to hospital water system outbreaks.