Nebulizers Often Harbor Harmful Pathogens
French researchers reporting in the October issue of the American Journal of Infection Control managed to culture Pseudomonas aeruginosa from 17 of 44 nebulizers used by cystic fibrosis patients who harbored P. aeruginosa infections. In addition, 14 of the patients nebulizers were contaminated with Staphylococcus aureus, one with Haemophilus bacteria, and six with yeast.
Nebulizer contamination with P. aeurginosa was more common among cystic fibrosis patients who were heavily infected with the bacterium. Thirteen of the 27 patients whose sputum samples contained more than 10 million colony-forming units (CFU) per milliliter of P. aeruginosa also had a nebulizer contaminated with the organism. In contrast, just four of the nebulizers from 17 patients with lower levels of infection were contaminated with P. aeruginosa.
The study ran from March 1996 to June 1997 and involved P. aeruginosa-infected cystic fibrosis patients seven years of age or older. Initially, the researchers enrolled patients whose sputum P. aeruginosa levels were 1 million CFU/mL or higher. Because of the difficulty of recruiting patients with this level of infection, the research team later lowered the infection threshold to 100,000 CFU/mL.
All of the patients used a nebulizer to administer dornase alfa, a recombinant enzyme that cleaves DNA molecules. The drug is used by cystic fibrosis patients to improve lung function and reduce the incidence of respiratory-tract infections.
Each study enrollees P. aeruginosa infection was confirmed by sputum culture at least two weeks before the study began and again on the day of the study. On the study day, each patient received a single dose of dornase alfa, delivered using a single-patient nebulizer and a compressor.
At the end of the aerosol session, the researchers attempted to culture microorganisms from water rinsed from 10 of the 44 nebulizers. One nebulizer was tested for contamination after three hours, 13 after six hours, and the remaining 20 were tested after 24 hours. The extent or likelihood of nebulizer contamination did not increase over time.
According to the researchers, nebulizers that contain pathogenic microorganisms could pose a serious risk of lung infection, particularly among patients with an immune-system deficiency. Nebulizers and associated equipment, said the researchers, are difficult to disinfect. Many patients do not clean their nebulizers each day. Because of these factors, the researchers recommended that disposable nebulizer equipment be used by patients who are at high risk for contracting an infection.