title: Shiga toxin 2 overexpression in Escherichia coli O157:H7 strains associated with severe human disease.
abstract: Variation in disease severity among Escherichia coli O157:H7 infections may result from differential expression of Shiga toxin 2 (Stx2). Eleven strains belonging to four prominent phylogenetic clades, including clade 8 strains representative of the 2006 U.S. spinach outbreak, were examined for stx2 expression by real-time PCR and western blot analysis. Clade 8 strains were shown to overexpress stx2 basally, and following induction with ciprofloxacin when compared to strains from clades 1-3. Differences in stx2 expression generally correlated with Stx2 protein levels. Single-nucleotide polymorphisms identified in regions upstream of stx2AB in clade 8 strains were largely absent in non-clade 8 strains. This study concludes that stx2 overexpression is common to strains from clade 8 associated with hemolytic uremic syndrome, and describes SNPs which may affect stx2 expression and which could be useful in the genetic differentiation of highly-virulent strains.
authors.affiliation: Microbial Evolution and Epidemiology Laboratory, Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, United States.
authors.forename: Mahesh
authors.initials: M
authors.lastname: Neupane
authors.forename: Galeb S
authors.initials: GS
authors.lastname: Abu-Ali
authors.forename: Avishek
authors.initials: A
authors.lastname: Mitra
authors.forename: David W
authors.initials: DW
authors.lastname: Lacher
authors.forename: Shannon D
authors.initials: SD
authors.lastname: Manning
authors.forename: James T
authors.initials: JT
authors.lastname: Riordan
mesh_terms: D016000:Cluster Analysis; D004196:Disease Outbreaks; D004927:Escherichia coli Infections / Q000150:complications / Q000453:epidemiology / Q000382:microbiology*; D019453:Escherichia coli O157 / Q000145:classification / Q000235:genetics / Q000302:isolation & purification / Q000472:pathogenicity*; D015870:Gene Expression; D006463:Hemolytic-Uremic Syndrome / Q000453:epidemiology / Q000382:microbiology*; D006801:Humans; D058889:Molecular Typing; D020641:Polymorphism, Single Nucleotide; D022641:Shiga Toxin 2 / Q000096:biosynthesis*; D018724:Spinacia oleracea / Q000382:microbiology; D014481:United States / Q000453:epidemiology; D014774:Virulence
chemical_list: D022641:Shiga Toxin 2