title: Next generation sequencing analysis of nine Corynebacterium ulcerans isolates reveals zoonotic transmission and a novel putative diphtheria toxin-encoding pathogenicity island.
abstract: BACKGROUND
  Toxigenic Corynebacterium ulcerans can cause a diphtheria-like illness in humans and have been found in domestic animals, which were suspected to serve as reservoirs for a zoonotic transmission. Additionally, toxigenic C. ulcerans were reported to take over the leading role in causing diphtheria in the last years in many industrialized countries.
  
  
  METHODS
  To gain deeper insights into the tox gene locus and to understand the transmission pathway in detail, we analyzed nine isolates derived from human patients and their domestic animals applying next generation sequencing and comparative genomics.
  
  
  RESULTS
  We provide molecular evidence for zoonotic transmission of C. ulcerans in four cases and demonstrate the superior resolution of next generation sequencing compared to multi-locus sequence typing for epidemiologic research. Additionally, we provide evidence that the virulence of C. ulcerans can change rapidly by acquisition of novel virulence genes. This mechanism is exemplified by an isolate which acquired a prophage not present in the corresponding isolate from the domestic animal. This prophage contains a putative novel virulence factor, which shares high identity with the RhuM virulence factor from Salmonella enterica but which is unknown in Corynebacteria so far. Furthermore, we identified a putative pathogenicity island for C. ulcerans bearing a diphtheria toxin gene.
  
  
  CONCLUSIONS
  The novel putative diphtheria toxin pathogenicity island could provide a new and alternative pathway for Corynebacteria to acquire a functional diphtheria toxin-encoding gene by horizontal gene transfer, distinct from the previously well characterized phage infection model. The novel transmission pathway might explain the unexpectedly high number of toxigenic C. ulcerans.
authors.affiliation: LGL, Bavarian Health and Food Safety Authority, Oberschleißheim, 85764 Germany.
authors.forename: Dominik M
authors.initials: DM
authors.lastname: Meinel
authors.affiliation: LGL, Bavarian Health and Food Safety Authority, Oberschleißheim, 85764 Germany.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Margos
authors.affiliation: LGL, Bavarian Health and Food Safety Authority, Oberschleißheim, 85764 Germany ; National Consiliary Laboratory on Diphtheria, Oberschleißheim, 85764 Germany.
authors.forename: Regina
authors.initials: R
authors.lastname: Konrad
authors.affiliation: Laboratory for Functional Genome Analysis, Gene Center, Ludwig-Maximilians-University Munich, Munich, 81377 Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Krebs
authors.affiliation: Laboratory for Functional Genome Analysis, Gene Center, Ludwig-Maximilians-University Munich, Munich, 81377 Germany.
authors.forename: Helmut
authors.initials: H
authors.lastname: Blum
authors.affiliation: LGL, Bavarian Health and Food Safety Authority, Oberschleißheim, 85764 Germany ; National Consiliary Laboratory on Diphtheria, Oberschleißheim, 85764 Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Sing