Population structure of Pseudomonas aeruginosa in CF and COPD

Chronic airway infections with Pseudomonas aeruginosa are common in individuals with bronchiectasis or cystic fibrosis (CF). P. aeruginosa can also be isolated from the sputum of adults with chronic obstructive pulmonary disease (COPD), but the role of the organism in the course of the disease is less well characterized than in other clinical settings. The population genetics of P. aeruginosa in these diseases and in acute infections was investigated by a microarray analysis representing the core genome by single nucleotide polymorphisms and the accessory genome by markers of genomic islets and islands, yielding an identification fidelity >99,8%.

612 sequential P. aeruginosa isolates from 36 CF patients treated at two large CF clinics (collected over a period of 20 years) were genotyped. The distribution of CF clones was compared with the global population structure and the influence of adaptive radiation and clade on the clinical course and the severity of the infection were analyzed. 134 P. aeruginosa isolates collected from 39 adults with COPD (colonization up to ten years) were genotyped and compared to the world-wide P. aeruginosa population.

In both CF and COPD, the spectrum of the infecting clones was comparable (e.g. most abundant clones were the globally dominant clones PA14 and C), but different from the distribution of strains causing acute infections like pneumonia or keratitis. Additionally, the carriage patterns of P. aeruginosa were different in CF and COPD. For example, the intraclonal microevolution and a frequent turnover or loss of clones are typical for the infections with P. aeruginosa in COPD. Only seven of the 39 patients (18%) were persistently colonized with the same P. aeruginosa clone for several years. In contrast, 60% of the chronically colonized CF patients at the CF clinic Hannover still harboured the initially acquired P. aeruginosa clone after more than ten years of colonization.