title: Genotypic Diversity within a Single Pseudomonas aeruginosa Strain Commonly Shared by Australian Patients with Cystic Fibrosis.
abstract: In cystic fibrosis (CF), Pseudomonas aeruginosa undergoes intra-strain genotypic and phenotypic diversification while establishing and maintaining chronic lung infections. As the clinical significance of these changes is uncertain, we investigated intra-strain diversity in commonly shared strains from CF patients to determine if specific gene mutations were associated with increased antibiotic resistance and worse clinical outcomes. Two-hundred-and-one P. aeruginosa isolates (163 represented a dominant Australian shared strain, AUST-02) from two Queensland CF centres over two distinct time-periods (2001-2002 and 2007-2009) underwent mexZ and lasR sequencing. Broth microdilution antibiotic susceptibility testing in a subset of isolates was also performed. We identified a novel AUST-02 subtype (M3L7) in adults attending a single Queensland CF centre. This M3L7 subtype was multi-drug resistant and had significantly higher antibiotic minimum inhibitory concentrations than other AUST-02 subtypes. Prospective molecular surveillance using polymerase chain reaction assays determined the prevalence of the 'M3L7' subtype at this centre during 2007-2009 (170 patients) and 2011 (173 patients). Three-year clinical outcomes of patients harbouring different strains and subtypes were compared. MexZ and LasR sequences from AUST-02 isolates were more likely in 2007-2009 than 2001-2002 to exhibit mutations (mexZ: odds ratio (OR) = 3.8; 95% confidence interval (CI): 1.1-13.5 and LasR: OR = 2.5; 95%CI: 1.3-5.0). Surveillance at the adult centre in 2007-2009 identified M3L7 in 28/509 (5.5%) P. aeruginosa isolates from 13/170 (7.6%) patients. A repeat survey in 2011 identified M3L7 in 21/519 (4.0%) P. aeruginosa isolates from 11/173 (6.4%) patients. The M3L7 subtype was associated with greater intravenous antibiotic and hospitalisation requirements, and a higher 3-year risk of death/lung transplantation, than other AUST-02 subtypes (adjusted hazard ratio [HR] = 9.4; 95%CI: 2.2-39.2) and non-AUST-02 strains (adjusted HR = 4.8; 95%CI: 1.4-16.2). This suggests ongoing microevolution of the shared CF strain, AUST-02, was associated with an emerging multi-drug resistant subtype and possibly poorer clinical outcomes.
authors.affiliation: Queensland Children's Medical Research Institute, Children's Health Queensland, South Brisbane, Queensland, Australia.|Adult Cystic Fibrosis Centre, Department of Thoracic Medicine, The Prince Charles Hospital, Chermside, Queensland, Australia.|School of Medicine, The University of Queensland, Herston, Queensland, Australia.
authors.forename: Anna Sze
authors.initials: AS
authors.lastname: Tai
authors.affiliation: Adult Cystic Fibrosis Centre, Department of Thoracic Medicine, The Prince Charles Hospital, Chermside, Queensland, Australia.|QIMR Berghofer Medical Research Institute, Herston, Queensland, Australia.
authors.forename: Scott Cameron
authors.initials: SC
authors.lastname: Bell
authors.affiliation: Queensland Children's Medical Research Institute, Children's Health Queensland, South Brisbane, Queensland, Australia.|Centre for Infection and Immunity, Queen's University Belfast, Belfast, United Kingdom.
authors.forename: Timothy James
authors.initials: TJ
authors.lastname: Kidd
authors.affiliation: Queensland Children's Medical Research Institute, Children's Health Queensland, South Brisbane, Queensland, Australia.|School of Medicine, The University of Queensland, Herston, Queensland, Australia.
authors.forename: Ella
authors.initials: E
authors.lastname: Trembizki
authors.affiliation: Queensland Children's Medical Research Institute, Children's Health Queensland, South Brisbane, Queensland, Australia.
authors.forename: Cameron
authors.initials: C
authors.lastname: Buckley
authors.affiliation: Queensland Children's Medical Research Institute, Children's Health Queensland, South Brisbane, Queensland, Australia.|School of Medicine, The University of Queensland, Herston, Queensland, Australia.
authors.forename: Kay Annette
authors.initials: KA
authors.lastname: Ramsay
authors.affiliation: Queensland Children's Medical Research Institute, Children's Health Queensland, South Brisbane, Queensland, Australia.|School of Population Health, The University of Queensland, Herston, Queensland, Australia.
authors.forename: Michael
authors.initials: M
authors.lastname: David
authors.affiliation: Queensland Children's Medical Research Institute, Children's Health Queensland, South Brisbane, Queensland, Australia.|Department of Respiratory and Sleep Medicine, Lady Cilento Children's Hospital, South Brisbane, Queensland, Australia.
authors.forename: Claire Elizabeth
authors.initials: CE
authors.lastname: Wainwright
authors.affiliation: Queensland Children's Medical Research Institute, Children's Health Queensland, South Brisbane, Queensland, Australia.|Menzies Health Institute Queensland, Griffith University and the Gold Coast University Hospital, Gold Coast, Queensland, Australia.
authors.forename: Keith
authors.initials: K
authors.lastname: Grimwood
authors.affiliation: Queensland Children's Medical Research Institute, Children's Health Queensland, South Brisbane, Queensland, Australia.|Pathology Queensland Central Laboratory, Herston, Queensland, Australia.
authors.forename: David Mark
authors.initials: DM
authors.lastname: Whiley
mesh_terms: D000328:Adult; D000900:Anti-Bacterial Agents / Q000494:pharmacology / Q000627:therapeutic use; D001315:Australia; D003550:Cystic Fibrosis / Q000382:microbiology*; D005260:Female; D005798:Genes, Bacterial; D014644:Genetic Variation; D006801:Humans; D008297:Male; D008826:Microbial Sensitivity Tests; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000235:genetics*; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D000900:Anti-Bacterial Agents