title: Comparative genomic analysis of two novel sporadic Shiga toxin-producing Escherichia coli O104:H4 strains isolated 2011 in Germany.
abstract: A large outbreak of gastrointestinal disease occurred in 2011 in Germany which resulted in almost 4000 patients with acute gastroenteritis or hemorrhagic colitis, 855 cases of a hemolytic uremic syndrome and 53 deaths. The pathogen was an uncommon, multiresistant Escherichia coli strain of serotype O104:H4 which expressed a Shiga toxin characteristic of enterohemorrhagic E. coli and in addition virulence factors common to enteroaggregative E. coli. During post-epidemic surveillance of Shiga toxin-producing E. coli (STEC) all but two of O104:H4 isolates were indistinguishable from the epidemic strain. Here we describe two novel STEC O104:H4 strains isolated in close spatiotemporal proximity to the outbreak which show a virulence gene panel, a Shiga toxin-mediated cytotoxicity towards Vero cells and aggregative adherence to Hep-2 cells comparable to the outbreak strain. They differ however both from the epidemic strain and from each other, by their antibiotic resistance phenotypes and some other features as determined by routine epidemiological subtyping methods. Whole genome sequencing of these two strains, of ten outbreak strain isolates originating from different time points of the outbreak and of one historical sporadic EHEC O104:H4 isolate was performed. Sequence analysis revealed a clear phylogenetic distance between the two variant strains and the outbreak strain finally identifying them as epidemiologically unrelated isolates from sporadic cases. These findings add to the knowledge about this emerging pathogen, illustrating a certain diversity within the bacterial core genome as well as loss and gain of accessory elements. Our results do also support the view that distinct new variants of STEC O104:H4 repeatedly might originate from yet unknown reservoirs, rather than that there would be a continuous diversification of a single epidemic strain established and circulating in Germany after the large outbreak in 2011.
authors.affiliation: Department of Infectious Diseases, Division of Enteropathogenic Bacteria and Legionella, National Reference Centre for Salmonella and other Bacterial Enteric Pathogens, Wernigerode Branch of Robert Koch-Institute, Berlin, Germany.
authors.forename: Erhard
authors.initials: E
authors.lastname: Tietze
authors.affiliation: Centre for Biological Threats and Special Pathogens, Robert Koch-Institute, Berlin, Germany.
authors.forename: Piotr Wojciech
authors.initials: PW
authors.lastname: Dabrowski
authors.affiliation: Department of Infectious Diseases, Division of Enteropathogenic Bacteria and Legionella, National Reference Centre for Salmonella and other Bacterial Enteric Pathogens, Wernigerode Branch of Robert Koch-Institute, Berlin, Germany.
authors.forename: Rita
authors.initials: R
authors.lastname: Prager
authors.affiliation: Centre for Biological Threats and Special Pathogens, Robert Koch-Institute, Berlin, Germany.
authors.forename: Aleksandar
authors.initials: A
authors.lastname: Radonic
authors.affiliation: Department of Infectious Diseases, Division of Enteropathogenic Bacteria and Legionella, National Reference Centre for Salmonella and other Bacterial Enteric Pathogens, Wernigerode Branch of Robert Koch-Institute, Berlin, Germany.
authors.forename: Angelika
authors.initials: A
authors.lastname: Fruth
authors.affiliation: Department of Infectious Diseases, Division of Enteropathogenic Bacteria and Legionella, National Reference Centre for Salmonella and other Bacterial Enteric Pathogens, Wernigerode Branch of Robert Koch-Institute, Berlin, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Auraß
authors.affiliation: Centre for Biological Threats and Special Pathogens, Robert Koch-Institute, Berlin, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Nitsche
authors.affiliation: Department of Infectious Diseases, Robert Koch-Institute, Berlin, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Mielke
authors.affiliation: Department of Infectious Diseases, Division of Enteropathogenic Bacteria and Legionella, National Reference Centre for Salmonella and other Bacterial Enteric Pathogens, Wernigerode Branch of Robert Koch-Institute, Berlin, Germany.
authors.forename: Antje
authors.initials: A
authors.lastname: Flieger
mesh_terms: D000818:Animals; D001422:Bacterial Adhesion; D002522:Chlorocebus aethiops; D004269:DNA, Bacterial / Q000235:genetics; D004196:Disease Outbreaks; D004927:Escherichia coli Infections / Q000453:epidemiology / Q000382:microbiology*; D016680:Genome, Bacterial; D005858:Germany / Q000453:epidemiology; D056945:Hep G2 Cells; D006801:Humans; D008969:Molecular Sequence Data; D010802:Phylogeny; D010957:Plasmids / Q000235:genetics; D020641:Polymorphism, Single Nucleotide; D017422:Sequence Analysis, DNA; D065288:Serogroup; D054323:Shiga-Toxigenic Escherichia coli / Q000145:classification / Q000235:genetics / Q000472:pathogenicity; D014709:Vero Cells; D014774:Virulence / Q000235:genetics
chemical_list: D004269:DNA, Bacterial
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