title: Analysis of a long-term outbreak of XDR Pseudomonas aeruginosa: a molecular epidemiological study.
abstract: OBJECTIVE
  Here we report on a long-term outbreak from 2009 to 2012 with an XDR Pseudomonas aeruginosa on two wards at a university hospital in southern Germany.
  
  
  METHODS
  Whole-genome sequencing was performed on the outbreak isolates and a core genome was constructed for molecular epidemiological analysis. We applied a time-place-sequence algorithm to improve estimation of transmission probabilities.
  
  
  RESULTS
  By using conventional infection control methods we identified 49 P. aeruginosa strains, including eight environmental isolates that belonged to ST308 (by MLST) and carried the metallo-β-lactamase IMP-8. Phylogenetic analysis on the basis of a non-recombinant core genome that contained 22 outbreak-specific SNPs revealed a pattern of four dominant clades with a strong phylogeographic structure and allowed us to determine the potential temporal origin of the outbreak to July 2008, 1 year before the index case was diagnosed. Superspreaders at the root of clades exhibited a high number of probable and predicted transmissions, indicating their exceptional position in the outbreak.
  
  
  CONCLUSIONS
  Our results suggest that the initial expansion of dominant sublineages was driven by a few superspreaders, while environmental contamination seemed to sustain the outbreak for a long period despite regular environmental control measures.
authors.affiliation: Institute of Medical Microbiology and Hygiene, University of Tübingen, Tübingen, Germany German Center for Infection Research (DZIF), partner site Tübingen, Tübingen, Germany will80@gmx.de.
authors.forename: Matthias
authors.initials: M
authors.lastname: Willmann
authors.affiliation: Genomic and Epigenomic Variation in Disease Group, Centre for Genomic Regulation (CRG), Barcelona, Spain Universitat Pompeu Fabra (UPF), Barcelona, Spain.
authors.forename: Daniela
authors.initials: D
authors.lastname: Bezdan
authors.affiliation: Genomic and Epigenomic Variation in Disease Group, Centre for Genomic Regulation (CRG), Barcelona, Spain Universitat Pompeu Fabra (UPF), Barcelona, Spain.
authors.forename: Luis
authors.initials: L
authors.lastname: Zapata
authors.affiliation: Genomic and Epigenomic Variation in Disease Group, Centre for Genomic Regulation (CRG), Barcelona, Spain Universitat Pompeu Fabra (UPF), Barcelona, Spain.
authors.forename: Hana
authors.initials: H
authors.lastname: Susak
authors.affiliation: Medical Center, Department of Hematology, Oncology, Immunology, Rheumatology & Pulmonology, University of Tübingen, Tübingen, Germany.
authors.forename: Wichard
authors.initials: W
authors.lastname: Vogel
authors.affiliation: Institute of Medical Microbiology and Hygiene, University of Tübingen, Tübingen, Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Schröppel
authors.affiliation: Institute of Medical Microbiology and Hygiene, University of Tübingen, Tübingen, Germany German Center for Infection Research (DZIF), partner site Tübingen, Tübingen, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Liese
authors.affiliation: Institute of Medical Microbiology and Hygiene, University of Tübingen, Tübingen, Germany German Center for Infection Research (DZIF), partner site Tübingen, Tübingen, Germany.
authors.forename: Christopher
authors.initials: C
authors.lastname: Weidenmaier
authors.affiliation: Institute of Medical Microbiology and Hygiene, University of Tübingen, Tübingen, Germany German Center for Infection Research (DZIF), partner site Tübingen, Tübingen, Germany.
authors.forename: Ingo B
authors.initials: IB
authors.lastname: Autenrieth
authors.affiliation: Genomic and Epigenomic Variation in Disease Group, Centre for Genomic Regulation (CRG), Barcelona, Spain Universitat Pompeu Fabra (UPF), Barcelona, Spain.
authors.forename: Stephan
authors.initials: S
authors.lastname: Ossowski
authors.affiliation: Institute of Medical Microbiology and Hygiene, University of Tübingen, Tübingen, Germany German Center for Infection Research (DZIF), partner site Tübingen, Tübingen, Germany.
authors.forename: Silke
authors.initials: S
authors.lastname: Peter
mesh_terms: D004196:Disease Outbreaks; D018562:Disease Transmission, Infectious; D024901:Drug Resistance, Multiple, Bacterial; D004783:Environmental Microbiology; D016021:Epidemiologic Studies; D016680:Genome, Bacterial; D005858:Germany / Q000453:epidemiology; D006785:Hospitals, University; D006801:Humans; D017720:Molecular Epidemiology; D058889:Molecular Typing; D011552:Pseudomonas Infections / Q000453:epidemiology* / Q000382:microbiology* / Q000635:transmission; D011550:Pseudomonas aeruginosa / Q000145:classification* / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D017422:Sequence Analysis, DNA; D062211:Spatio-Temporal Analysis
keywords: IMP carbapenemase; outbreak investigation; transmission analysis; whole-genome sequencing