Viability ofPseudomonas aeruginosain cough aerosols generated by persons with cystic fibrosis

Abstract

BackgroundPerson-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.MethodsUsing 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.ResultsNineteen 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.ConclusionsViable P aeruginosa in cough aerosols travel further and last longer than recognised previously, providing additional evidence of airborne transmission between patients with CF.

Cystic fibrosis pathogens survive for extended periods within cough-generated droplet nuclei

“…The experimental equipment comprised of two validated, independent systems to study the distance travelled and survival duration of bacteria contained in aerosols generated during coughing 5. Participants completed five cough experiments; distance studies involved aerosol sampling at 2 and 4 m, while the duration studies involved the ageing of cough aerosol samples for 5, 15 and 45 min prior to extraction 5.…”

Epidemiology of infection and current guidelines for infection prevention in cystic fibrosis patients

“…The authors calculated that 90% of viable bacteria would be removed in 50 min at a ventilation rate of two air changes per hour, and in 13 min at 10 air changes per hour. 26 Significant variability was observed in aerosol production between different patients. Cough aerosol quantity correlated with sputum bacterial load.…”

Air Contamination with Bacteria in Cystic Fibrosis Clinics: Implications for Prevention Strategies

“…We previously reported that 8% of air samples obtained z3 feet from participants in CF clinics contained their respiratory tract pathogens (12). Cough aerosols from patients with CF contained infectious droplets within the respirable range that traveled 6-12 feet (13,14). Recently, patient-to-patient transmission of Mycobacterium abscessus occurred in a CF clinic, and airborne transmission was postulated (15).…”