Phenotypic and genotypic characteristics of Pseudomonas aeruginosa isolated from cystic fibrosis patients with chronic infections

Abstract

Patients with cystic fibrosis are predisposed to chronic respiratory tract infections caused by Pseudomonas aeruginosa. As the disease progresses, the microorganism diversifies into genotypically and phenotypically different strains which may coexist in the patient's airways for years. Adaptation of the microorganism to the airways of patients with cystic fibrosis probably occurs in response to the host's airway environment, the elements of the immune system and antibiotic therapy. Due to the chronic persistence of the microorganism in the airways, a comprehensive molecular analysis was conducted. The analysis included 120 strains isolated from 10 adult cystic fibrosis patients with chronic P. aeruginosa infection. The aim of the study was to analyze the molecular patterns of P. aeruginosa strains and to trace their transmission in the population of cystic fibrosis patients, as well as to study a relationship of the disease with specific phenotypic features. In the research, a genotypic analysis of P. aeruginosa was performed using pulsed-field gel electrophoresis. The results of a number of phenotypic features of the strains were added to the outcomes of the molecular studies. As a result, 28 different genotypes were distinguished. The study also showed cross-transmission of strains between patients. 3 transmissible clusters were identified, including IG1 and IG2 clusters with 9 strains of P. aeruginosa each, obtained from 2 patients and IG3 cluster with 6 strains of P. aeruginosa isolated from 3 patients. Moreover, it was found that in some patients, several unrelated strains of P. aeruginosa may transiently or permanently infect the respiratory tract. A comprehensive understanding of the P. aeruginosa adaptation may help to develop more effective antimicrobial therapies and to identify new targets for future drugs in order to prevent progression of the infection to chronic stages.

Figure 1

Distribution of 120 P. aeruginosa isolates belonging to different PFGE types among 10 cystic fibrosis patients.

Figure 2

Comparison of P. aeruginosa isolates between transmissible (n = 24) (blue) and non-transmissible (n = 96) (orange) P. aeruginosa isolates. Isolates were characterized for protease (a), elastase (b), swimming (c), swarming (d) and twitching (e) motility; biofilm CV (biomass) (f); MTT cell viability assay (g), pyocyanin production (h) and mucoid phenotype (i). Black horizontal bars represent the mean of each group.