title: Enterohemorrhagic Escherichia coli O26:H11/H-: a new virulent clone emerges in Europe.
abstract: BACKGROUND
  Enterohemorrhagic Escherichia coli (EHEC) O26 causes diarrhea and hemolytic uremic syndrome (HUS). Strains harboring the stx1a gene prevail, but strains with stx2a as the sole Shiga toxin-encoding gene are now emerging. The traits and virulence of the latter set of strains are unknown. We correlated stx genotypes of 272 EHEC O26 strains isolated in 7 European countries between 1996 and 2012 with disease phenotypes. We determined phylogeny, clonal structure, and plasmid gene profiles of the isolates and portray geographic and temporal distribution of the different subgroups.
  
  
  METHODS
  The stx genotypes and plasmid genes were identified using polymerase chain reaction, phylogeny was assigned using multilocus sequence typing, and clonal relatedness was established using pulsed-field gel electrophoresis.
  
  
  RESULTS
  Of the 272 EHEC O26 isolates, 107 (39.3%), 139 (51.1%), and 26 (9.6%) possessed stx1a, stx2a, or both genes, respectively. Strains harboring stx2a only were significantly associated with HUS (odds ratio, 14.2; 95% confidence interval, 7.9-25.6; P < .001) compared to other stx genotypes. The stx2a-harboring strains consist of 2 phylogenetically distinct groups defined by sequence type (ST) 21 and ST29. The ST29 strains are highly conserved and correspond by plasmid genes to the new virulent clone of EHEC O26 that emerged in Germany in the 1990s. This new clone occurred in 6 of the 7 countries and represented approximately 50% of all stx2a-harboring EHEC O26 strains isolated between 1996 and 2012.
  
  
  CONCLUSIONS
  A new highly virulent clone of EHEC O26 has emerged in Europe. Its reservoirs and sources warrant identification.
authors: Institute for Hygiene and the National Consulting Laboratory on Hemolytic Uremic Syndrome, University of Münster, Wernigerode, Germany. mbiela@uni-muenster.de
authors: Martina
authors: M
authors: Bielaszewska
authors: Alexander
authors: A
authors: Mellmann
authors: Stefan
authors: S
authors: Bletz
authors: Wenlan
authors: W
authors: Zhang
authors: Robin
authors: R
authors: Köck
authors: Annelene
authors: A
authors: Kossow
authors: Rita
authors: R
authors: Prager
authors: Angelika
authors: A
authors: Fruth
authors: Dorothea
authors: D
authors: Orth-Höller
authors: Monika
authors: M
authors: Marejková
authors: Stefano
authors: S
authors: Morabito
authors: Alfredo
authors: A
authors: Caprioli
authors: Denis
authors: D
authors: Piérard
authors: Geraldine
authors: G
authors: Smith
authors: Claire
authors: C
authors: Jenkins
authors: Katarína
authors: K
authors: Curová
authors: Helge
authors: H
authors: Karch
mesh_terms: D000293:Adolescent; D000328:Adult; D000900:Anti-Bacterial Agents / Q000494:pharmacology / Q000627:therapeutic use; D016009:Chi-Square Distribution; D002648:Child; D002675:Child, Preschool; D004269:DNA, Bacterial / Q000235:genetics; D016521:Electrophoresis, Gel, Pulsed-Field; D054324:Enterohemorrhagic Escherichia coli / Q000235:genetics / Q000302:isolation & purification* / Q000472:pathogenicity; D004927:Escherichia coli Infections / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology*; D005060:Europe / Q000453:epidemiology; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008826:Microbial Sensitivity Tests; D010641:Phenotype; D010802:Phylogeny; D010957:Plasmids / Q000235:genetics; D016133:Polymerase Chain Reaction; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial