title: Chromosomal dynamism in progeny of outbreak-related sorbitol-fermenting enterohemorrhagic Escherichia coli O157:NM.
abstract: Sorbitol-fermenting (SF) enterohemorrhagic Escherichia coli (EHEC) O157:NM (nonmotile) is a unique clone that causes outbreaks of hemorrhagic colitis and hemolytic-uremic syndrome. In well-defined clusters of cases, we have observed significant variability in pulsed-field gel electrophoresis (PFGE) patterns which could indicate coinfection by different strains. An analysis of randomly selected progeny colonies of an outbreak strain after subcultivation demonstrated that they displayed either the cognate PFGE outbreak pattern or one of four additional patterns and were <89% similar. These profound alterations were associated with changes in the genomic position of one of two Shiga toxin 2-encoding genes (stx2) in the outbreak strain or with the loss of this gene. The two stx2 alleles in the outbreak strain were identical but were flanked with phage-related sequences with only 77% sequence identity. Neither of these phages produced plaques, but one lysogenized E. coli K-12 and integrated in yecE in the lysogens and the wild-type strain. The presence of two stx2 genes which correlated with increased production of Stx2 in vitro but not with the clinical outcome of infection was also found in 14 (21%) of 67 SF EHEC O157:NM isolates from sporadic cases of human disease. The variability of PFGE patterns for the progeny of a single colony must be considered when interpreting PFGE patterns in SF EHEC O157-associated outbreaks.
authors.affiliation: Institut für Hygiene, Universität Münster, Robert Koch Str. 41, 48149 Münster, Germany. mbiela@uni-muenster.de
authors.forename: Martina
authors.initials: M
authors.lastname: Bielaszewska
authors.forename: Rita
authors.initials: R
authors.lastname: Prager
authors.forename: Wenlan
authors.initials: W
authors.lastname: Zhang
authors.forename: Alexander W
authors.initials: AW
authors.lastname: Friedrich
authors.forename: Alexander
authors.initials: A
authors.lastname: Mellmann
authors.forename: Helmut
authors.initials: H
authors.lastname: Tschäpe
authors.forename: Helge
authors.initials: H
authors.lastname: Karch
mesh_terms: D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000453:epidemiology / Q000382:microbiology; D002648:Child; D002876:Chromosomes, Bacterial / Q000235:genetics*; D004196:Disease Outbreaks; D016521:Electrophoresis, Gel, Pulsed-Field; D004927:Escherichia coli Infections / Q000453:epidemiology / Q000382:microbiology; D019453:Escherichia coli O157 / Q000145:classification / Q000235:genetics* / Q000254:growth & development / Q000302:isolation & purification; D005285:Fermentation; D020440:Gene Duplication; D006463:Hemolytic-Uremic Syndrome / Q000453:epidemiology* / Q000382:microbiology; D006801:Humans; D007223:Infant; D008297:Male; D008969:Molecular Sequence Data; D017422:Sequence Analysis, DNA; D022641:Shiga Toxin 2 / Q000235:genetics*; D013012:Sorbitol / Q000378:metabolism*
chemical_list: D022641:Shiga Toxin 2; D013012:Sorbitol