Viability of Pseudomonas aeruginosa in cough aerosols generated by persons with cystic fibrosis

Knibbs, Luke D., Johnson, Graham R., Kidd, Timothy J., Cheney, Joyce, Grimwood, Keith, Kattenbelt, Jacqueline A., O'Rourke, Peter K., Ramsay, Kay A., Sly, Peter D., Wainwright, Claire E., Wood, Michelle E., Morawska, Lidia and Bell, Scott C. (2014) Viability of Pseudomonas aeruginosa in cough aerosols generated by persons with cystic fibrosis. Thorax, 69 8: 740-745. doi:10.1136/thoraxjnl-2014-205213

Author Knibbs, Luke D.
Johnson, Graham R.
Kidd, Timothy J.
Cheney, Joyce
Grimwood, Keith
Kattenbelt, Jacqueline A.
O'Rourke, Peter K.
Ramsay, Kay A.
Sly, Peter D.
Wainwright, Claire E.
Wood, Michelle E.
Morawska, Lidia
Bell, Scott C.
Title Viability of Pseudomonas aeruginosa in cough aerosols generated by persons with cystic fibrosis
Formatted title
Viability of Pseudomonas aeruginosa in cough aerosols generated by persons with cystic fibrosis
Journal name Thorax   Check publisher's open access policy
ISSN 0040-6376
Publication date 2014-08-01
Sub-type Article (original research)
DOI 10.1136/thoraxjnl-2014-205213
Open Access Status DOI
Volume 69
Issue 8
Start page 740
End page 745
Total pages 6
Place of publication London, United Kingdom
Publisher B M J Group
Language eng
Formatted abstract
Background Person-to-person transmission of respiratory pathogens, including Pseudomonas aeruginosa, is a challenge facing many cystic fibrosis (CF) centres. Viable P aeruginosa are contained in aerosols produced during coughing, raising the possibility of airborne transmission.

Methods Using purpose-built equipment, we measured viable P aeruginosa in cough aerosols at 1, 2 and 4 m from the subject (distance) and after allowing aerosols to age for 5, 15 and 45 min in a slowly rotating drum to minimise gravitational settling and inertial impaction (duration). Aerosol particles were captured and sized employing an Anderson Impactor and cultured using conventional microbiology. Sputum was also cultured and lung function and respiratory muscle strength measured.

Results Nineteen patients with CF, mean age 25.8 (SD 9.2) years, chronically infected with P aeruginosa, and 10 healthy controls, 26.5 (8.7) years, participated. Viable P aeruginosa were detected in cough aerosols from all patients with CF, but not from controls; travelling 4 m in 17/18 (94%) and persisting for 45 min in 14/18 (78%) of the CF group. Marked inter-subject heterogeneity of P aeruginosa aerosol colony counts was seen and correlated strongly (r=0.73–0.90) with sputum bacterial loads. Modelling decay of viable P aeruginosa in a clinic room suggested that at the recommended ventilation rate of two air changes per hour almost 50 min were required for 90% to be removed after an infected patient left the room.

Conclusions Viable P aeruginosa in cough aerosols travel further and last longer than recognised previously, providing additional evidence of airborne transmission between patients with CF.

What is the key question?
▸ Several studies have suggested that airborne transmission of Pseudomonas aeruginosa among patients with cystic fibrosis (CF) is feasible; however, it is unclear how far cough generated aerosols travel or how long they remain viable in the airborne phase.

What is the bottom line?
▸ Using two validated cough aerosol sampling systems to measure the viability of P aeruginosa in droplet nuclei we demonstrate that patients with CF produce cough aerosols containing viable organisms that are capable of travelling up to 4 m and persisting in the air for up to 45 min.

Why read on?
▸ Data presented here challenge current CF infection control practices of separating patients by 1 – 2 m to prevent cross-infection by respiratory bacteria, suggesting a re-examination of current infection control practices within the CF community is needed.
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

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Created: Wed, 09 Jul 2014, 17:45:07 EST by Luke Knibbs on behalf of School of Public Health