Phenotypic and Genotypic Comparison of Epidemic and Non-Epidemic Strains of Pseudomonas aeruginosa from Individuals with Cystic Fibrosis

Abstract

Epidemic strains of Pseudomonas aeruginosa have been found worldwide among the cystic fibrosis (CF) patient population. Using pulse-field gel electrophoresis, the Prairie Epidemic Strain (PES) has recently been found in one-third of patients attending the Calgary Adult CF Clinic in Canada. Using multi-locus sequence typing, PES isolates from unrelated patients were found to consistently have ST192. Though most patients acquired PES prior to enrolling in the clinic, some patients were observed to experience strain replacement upon transitioning to the clinic whereby local non-epidemic P. aeruginosa isolates were displaced by PES. Here we genotypically and phenotypically compared PES to other P. aeruginosa epidemic strains (OES) found around the world as well as local non-epidemic CF P. aeruginosa isolates in order to characterize PES. Since some epidemic strains are associated with worse clinical outcomes, we assessed the pathogenic potential of PES to determine if these isolates are virulent, shared properties with OES, and if its phenotypic properties may offer a competitive advantage in displacing local non-epidemic isolates during strain replacement. As such, we conducted a comparative analysis using fourteen phenotypic traits, including virulence factor production, biofilm formation, planktonic growth, mucoidy, and antibiotic susceptibility to characterize PES, OES, and local non-epidemic isolates. We observed that PES and OES could be differentiated from local non-epidemic isolates based on biofilm growth with PES isolates being more mucoid. Pairwise comparisons indicated that PES produced significantly higher levels of proteases and formed better biofilms than OES but were more susceptible to antibiotic treatment. Amongst five patients experiencing strain replacement, we found that super-infecting PES produced lower levels of proteases and elastases but were more resistant to antibiotics compared to the displaced non-epidemic isolates. This comparative analysis is the first to be completed on a large scale between groups of epidemic and non-epidemic CF P. aeruginosa isolates.

Virulence adaptations of Pseudomonas aeruginosa isolated from patients with non-cystic fibrosis bronchiectasis

“…The median time between early and late isolate collection for patients was 3.16 years (range: 0.5-21.4 years). Our CF control cohort was derived from 28 patients chosen randomly from a collection of patients known to be infected with both unique and epidemic strains and included 39 early and 44 late isolates (Duong et al, 2015). The median time between early and late CF isolates collected was 14 years (range: 2-24 years).…”

“…Phenotypic clustering of virulence factors was done through the use of CLUSTER 3.0 (Stanford University) using the unweighted pair group method. The dendrogram was generated based on criteria set by Duong et al (2015) and visualized using Java TreeView (Saldanha, 2004).…”

Blocking the alternative sigma factor RpoN reduces virulence ofPseudomonas aeruginosaisolated from cystic fibrosis patients and increases antibiotic sensitivity in a laboratory strain

“…P. aeruginosa isolated from different CF patients or within the same CF patient have varied phenotypes and genotypes (39, 40). P. aeruginosa adapts over time, leading to mutations and changes in expression of genes related to motility, quorum sensing, and overall virulence (41, 43).…”

“…P. aeruginosa isolated from CF patients are highly variable (39, 40), with the rpoN gene often mutated or lost (41). The patient isolates evaluated in this study had a broad range of motility, biofilm formation, RpoN protein levels, and virulence in C. elegans .…”

“…P. aeruginosa isolated from CF patients are phenotypically and genetically varied (39, 40). Many P. aeruginosa clinical isolates have mutations, including deletion or loss of function, in the rpoN gene (41, 42).…”