Phenotypic heterogeneity of Pseudomonas aeruginosa populations in a cystic fibrosis patient.

Matthew L Workentine,Christopher D Sibley,Harvey R Rabin,Michael D Parkins,Bryan Glezerson,Michael G Surette,Jens C Norgaard-Gron,Swathi Purighalla,John R Battista

doi:10.1371/journal.pone.0060225

Matthew L Workentine, Christopher D Sibley + Show 7 more

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https://doi.org/10.1371/journal.pone.0060225

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Abstract

The opportunistic pathogen Pseudomonas aeruginosa chronically infects the lower airways of patients with cystic fibrosis. Throughout the course of infection this organism undergoes adaptations that contribute to its long-term persistence in the airways. While P. aeruginosa diversity has been documented, it is less clear to what extent within-patient diversity contributes to the overall population structure as most studies have been limited to the analysis of only a few isolates per patient per time point. To examine P. aeruginosa population structure in more detail we collected multiple isolates from individual sputum samples of a patient chronically colonized with P. aeruginosa. This strain collection, comprised of 169 clonal isolates and representing three pulmonary exacerbations as well as clinically stable periods, was assayed for a wide selection of phenotypes. These phenotypes included colony morphology, motility, quorum sensing, protease activity, auxotrophy, siderophore levels, antibiotic resistance, and growth profiles. Each phenotype displayed significant variation even within isolates of the same colony morphotype from the same sample. Isolates demonstrated a large degree of individuality across phenotypes, despite being part of a single clonal lineage, suggesting that the P. aeruginosa population in the cystic fibrosis airways is being significantly under-sampled.

Highlights

Cystic fibrosis (CF) is an autosomal recessive disorder where mutations in the CF transmembrane conductance regulator lead to altered ion flux and the reduction of fluid covering the surface of airway epithelial cells [1,2,3]
The source patient was a 31 year old male with advanced CF airways disease, whom had been chronically infected with P. aeruginosa for 20 years
Thirty-four expectorated sputum samples were collected from the patient over one year, and comprised 16 samples collected during periods of clinical stability and 18 samples collected through three acute pulmonary exacerbations during which the patient was hospitalized and treated with parenteral anti-pseudomonal therapies (Table S1)

Summary

Introduction

Cystic fibrosis (CF) is an autosomal recessive disorder where mutations in the CF transmembrane conductance regulator lead to altered ion flux and the reduction of fluid covering the surface of airway epithelial cells [1,2,3]. Compromised innate immunity including reduced mucociliary clearance in patients with CF, gives a variety of species the opportunity to colonize the lower airways, generating long-term complex bacterial infections [2,4,5,6]. P. aeruginosa infections in the lower airways can be maintained for decades. Throughout this time P. aeruginosa exhibits genetic and phenotypic diversity thought to occur as the organism adapts to the lower airway environment [20,21]. Some factors considered to be the hallmarks of P. aeruginosa adaption to the CF airways include a switch to the mucoid phenotype [22] and loss of motility [23]. It has been suggested that these colony variants have adaptations specific for persistence in the lower airways [27]

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