Cough-generated aerosols of Pseudomonas aeruginosa and other Gram-negative bacteria from patients with cystic fibrosis
- C E Wainwright1,2,
- M W France3,
- P O’Rourke4,
- S Anuj2,5,
- T J Kidd5,6,7,
- M D Nissen1,2,5,6,
- T P Sloots2,5,
- C Coulter8,
- Z Ristovski9,
- M Hargreaves9,
- B R Rose10,
- C Harbour10,
- S C Bell3,7,
- K P Fennelly11
- 1Royal Children’s Hospital and Health Service District, Brisbane, Australia
- 2Department of Paediatrics and Child Health, University of Queensland, Brisbane, Australia
- 3Thoracic Medicine, The Prince Charles Hospital, Brisbane, Australia
- 4Queensland Institute of Medical Research, Brisbane, Australia
- 5Qpid Laboratory, Sir Albert Sakzewski Virus Research Centre, Herston, Australia
- 6Pathology Queensland, Herston, Australia
- 7School of Medicine, University of Queensland, Brisbane, Australia
- 8Infectious Diseases, The Prince Charles Hospital, Brisbane, Australia
- 9IHBI Queensland University Technology, Brisbane, Australia
- 10Department of Infectious Diseases, University of Sydney, Sydney, Australia
- 11UMDNJ-New Jersey Medical School, New Jersey, USA
- Correspondence to Dr C E Wainwright, Department of Respiratory Medicine, Royal Children’s Hospital, Brisbane 4029, Australia;
- Received 15 December 2008
- Accepted 15 June 2009
- Published Online First 1 July 2009
Background: Pseudomonas aeruginosa is the most common bacterial pathogen in patients with cystic fibrosis (CF). Current infection control guidelines aim to prevent transmission via contact and respiratory droplet routes and do not consider the possibility of airborne transmission. It was hypothesised that subjects with CF produce viable respirable bacterial aerosols with coughing.
Methods: A cross-sectional study was undertaken of 15 children and 13 adults with CF, 26 chronically infected with P aeruginosa. A cough aerosol sampling system enabled fractioning of respiratory particles of different sizes and culture of viable Gram-negative non-fermentative bacteria. Cough aerosols were collected during 5 min of voluntary coughing and during a sputum induction procedure when tolerated. Standardised quantitative culture and genotyping techniques were used.
Results: P aeruginosa was isolated in cough aerosols of 25 subjects (89%), 22 of whom produced sputum samples. P aeruginosa from sputum and paired cough aerosols were indistinguishable by molecular typing. In four cases the same genotype was isolated from ambient room air. Approximately 70% of viable aerosols collected during voluntary coughing were of particles ⩽3.3 μm aerodynamic diameter. P aeruginosa, Burkholderia cenocepacia, Stenotrophomonas maltophilia and Achromobacter xylosoxidans were cultivated from respiratory particles in this size range. Positive room air samples were associated with high total counts in cough aerosols (p = 0.003). The magnitude of cough aerosols was associated with higher forced expiratory volume in 1 s (r = 0.45, p = 0.02) and higher quantitative sputum culture results (r = 0.58, p = 0.008).
Conclusion: During coughing, patients with CF produce viable aerosols of P aeruginosa and other Gram-negative bacteria of respirable size range, suggesting the potential for airborne transmission.
See Editorial, p 921
▸ Additional details are published online only at http://thorax.bmj.com/content/vol64/issue11
SCB and KPF contributed equally to this study.
Funding Supported by Royal Children’s Hospital Foundation, Brisbane, Australian Cystic Fibrosis Research Trust and a University of Queensland Travel Grant Award.
Competing interests None.
Ethics approval The study was approved by the ethics committees of both CF centres and the University of Queensland and the Institutional Review Board of UMDNJ. Informed consent was obtained from all subjects and in addition from the parents or guardians of all young people under 18 years of age.
Provenance and Peer review Not commissioned; externally peer reviewed.