Pseudomonas aeruginosa transcriptome analysis in a cystic fibrosis lung model reveals metabolic changes accompanying biofilm maturation and increased antibiotic tolerance over time

Abstract

AbstractThe opportunistic pathogen Pseudomonas aeruginosa forms biofilm infections in the lungs of people with the genetic condition cystic fibrosis (CF) that can persist for decades. There are numerous P. aeruginosa lifestyle changes associated with chronic biofilm infection cued by the CF lung environment. These include a loss of virulence, metabolic changes, and increased antimicrobial tolerance. We have investigated P. aeruginosa PA14 biofilm infection over 7 d in an ex vivo pig lung (EVPL) model for CF, previously shown to facilitate formation of a clinically-relevant P. aeruginosa biofilm structure with gene expression comparable to human infection. We extracted and sequenced P. aeruginosa RNA from EVPL-associated biofilms 24 h, 48 h, and 7 d after infection, and compared gene expression between sequential time points. We also investigated tolerance to polymyxins across these three time points. Our results indicate that the EVPL model can maintain a P. aeruginosa biofilm population, which exhibits increased antibiotic tolerance, for at least 7 d. Differential expression of antimicrobial resistance-associated genes was not observed, however there was significant upregulation of sulfur metabolism and phenazine biosynthesis-related genes, as well as maintenance of a structured biofilm. These findings provide further insight into the incidence of increased P. aeruginosa antibiotic tolerance during infection of the CF lung, and the gene expression changes that arise as chronic infection establishes.