Fine-Particle Humidifiers — Source of Pseudomonas aeruginosa Infections in a Respiratory-Disease Unit

Abstract

In a pulmonary-disease ward containing a respiratory-disease intensive-care unit, 9 per cent of the patients on the ward and one fifth to one third of those in the intensive-care unit harbored Pseudomonas aeruginosa in their respiratory tracts. Eight patients acquired pseudomonas pulmonary infections in the hospital.

The fine-particle aerosol from unheated room humidifiers (Walton "centrifugal atomizer," Model HA) was shown to cause heavy environmental contamination by Ps. aeruginosa. Air sampling by the settling plate method yielded 300 gram-negative bacteria, including pseudomonas, per square foot per minute. Pyocin typing was used to identify the endemic strains of pseudomonas in reservoir water, in room air and in the sputum of patients with chronic respiratory disease. Each of four respirators in the intensive-care unit propagated 6 × 10⁶ organisms per day. Decontamination of humidifiers by various means was unsatisfactory, and their use was discontinued.