Epidemiology and natural history ofPseudomonas aeruginosaairway infections in non-cystic fibrosis bronchiectasis

Abstract

The natural history and epidemiology of Pseudomonas aeruginosa infections in non-cystic fibrosis (non-CF) bronchiectasis is not well understood.As such it was our intention to determine the evolution of airway infection and the transmission potential of P. aeruginosa in patients with non-CF bronchiectasis.A longitudinal cohort study was conducted from 1986–2011 using a biobank of prospectively collected isolates from patients with non-CF bronchiectasis. Patients included were ≥18 years old and had ≥2 positive P. aeruginosa cultures over a minimum 6-month period. All isolates obtained at first and most recent clinical encounters, as well as during exacerbations, that were morphologically distinct on MacConkey agar were genotyped by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). A total of 203 isolates from 39 patients were analysed. These were compared to a large collection of globally epidemic and local CF strains, as well as non-CF isolates.We identified four patterns of infection in non-CF bronchiectasis including: 1) persistence of a single strain (n=26; 67%); 2) strain displacement (n=8; 20%); 3) temporary disruption (n=3; 8%); and 4) chaotic airway infection (n=2; 5%). Patterns of infection were not significant predictors of rates of lung function decline or progression to end-stage disease and acquisition of new strains did not associate with the occurrence of exacerbations. Rarely, non-CF bronchiectasis strains with similar pulsotypes were observed in CF and non-CF controls, but no CF epidemic strains were observed. While rare shared strains were observed in non-CF bronchiectasis, whole-genome sequencing refuted patient–patient transmission.We observed a higher incidence of strain-displacement in our patient cohort compared to those observed in CF studies, although this did not impact on outcomes.

Transmission of bacteria in bronchiectasis and chronic obstructive pulmonary disease: Low burden of cough aerosols

“…Our results found that no major Australian CF shared P. aeruginosa strains were detected in our current cohort. In fact, our study found no evidence of shared P. aeruginosa strain infections, which is in keeping with the published data that shared P. aeruginosa strains are uncommon in patients with bronchiectasis or COPD . The P. aeruginosa strains detected in our study are commonly found in other niches, such as the natural environment and non‐CF infections .…”

“…The P. aeruginosa strains detected in our study are commonly found in other niches, such as the natural environment and non‐CF infections . Our longitudinal analysis of P. aeruginosa isolates showed that the majority of participants retained the same unique P. aeruginosa strain over time, which is consistent with other recent studies . These results suggest that person‐to‐person transmission of P. aeruginosa is unlikely to occur in patients with bronchiectasis and COPD.…”

“…ERIC‐PCR banding patterns were visually analysed, with isolates showing a variance of ≥1 band allocated to a different rep‐PCR type. Furthermore, patterns of infection within patients were determined . Clinical records were reviewed to determine possible opportunities for cross‐infection, such as overlapping hospital admissions, outpatient clinic appointments (including lung function appointments if available) and emergency admissions.…”

“…13 Yet, unlike CF, cross-infection with P. aeruginosa is reported to be uncommon in patients with bronchiectasis and COPD. [14][15][16][17][18][19][20] Although the evidence for crossinfection is infrequent in non-CF suppurative lung diseases, 15,16 the transmission mechanism of possible person-to-person transmission events has not been studied previously. Therefore, we sought to determine if (i) patients with bronchiectasis or COPD can produce cough aerosols containing P. aeruginosa and (ii) if respiratory infections with shared P. aeruginosa strains occur in patients with bronchiectasis and COPD attending a centre that is co-located with a large adult CF centre.…”

“…In (non‐CF) bronchiectasis and chronic obstructive pulmonary disease (COPD), P. aeruginosa predominantly causes infection in those with severe disease and is associated with poorer prognosis, higher mortality and increased hospital admissions . Yet, unlike CF, cross‐infection with P. aeruginosa is reported to be uncommon in patients with bronchiectasis and COPD . Although the evidence for cross‐infection is infrequent in non‐CF suppurative lung diseases, the transmission mechanism of possible person‐to‐person transmission events has not been studied previously.…”