title: Differences in adherence and virulence gene expression between two outbreak strains of enterohaemorrhagic Escherichia coli O157 : H7.
abstract: The Escherichia coli O157 : H7 TW14359 strain was implicated in a multi-state outbreak in North America in 2006, which resulted in high rates of severe disease. Similarly, the O157 : H7 RIMD0509952 (Sakai) strain caused the largest O157 : H7 outbreak to date. Both strains were shown to represent divergent phylogenetic lineages. Here we compared global gene expression patterns before and after epithelial cell exposure, as well as the ability to adhere to and invade epithelial cells, between the two outbreak strains. Epithelial cell assays demonstrated a 2.5-fold greater adherence of the TW14359 strain relative to Sakai, while whole-genome microarrays detected significant differential expression of 914 genes, 206 of which had a fold change >/=1.5. Interestingly, most locus of enterocyte effacement (LEE) genes were upregulated in TW14359, whereas flagellar and chemotaxis genes were primarily upregulated in Sakai, suggesting discordant expression of these genes between the two strains. The Shiga toxin 2 genes were also upregulated in the TW14359 strain, as were several pO157-encoded genes that promote adherence, including type II secretion genes and their effectors stcE and adfO. Quantitative RT-PCR confirmed the expression differences detected in the microarray analysis, and expression levels were lower for a subset of LEE genes before versus after exposure to epithelial cells. In all, this study demonstrated the upregulation of major and ancillary virulence genes in TW14359 and of flagellar and chemotaxis genes in Sakai, under conditions that precede intimate bacterial attachment to epithelial cells. Differences in the level of adherence to epithelial cells were also observed, implying that these two phylogenetically divergent O157 : H7 outbreak strains vary in their ability to colonize, or initiate the disease process.
authors.affiliation: Microbial Evolution Laboratory, National Food Safety and Toxicology Center, Michigan State University, East Lansing, MI 48824, USA.
authors.forename: Galeb S
authors.initials: GS
authors.lastname: Abu-Ali
authors.affiliation: Microbial Evolution Laboratory, National Food Safety and Toxicology Center, Michigan State University, East Lansing, MI 48824, USA.
authors.forename: Lindsey M
authors.initials: LM
authors.lastname: Ouellette
authors.affiliation: Microbial Evolution Laboratory, National Food Safety and Toxicology Center, Michigan State University, East Lansing, MI 48824, USA.
authors.forename: Scott T
authors.initials: ST
authors.lastname: Henderson
authors.affiliation: Microbial Evolution Laboratory, National Food Safety and Toxicology Center, Michigan State University, East Lansing, MI 48824, USA.
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Whittam
authors.affiliation: Microbial Evolution Laboratory, National Food Safety and Toxicology Center, Michigan State University, East Lansing, MI 48824, USA.
authors.forename: Shannon D
authors.initials: SD
authors.lastname: Manning
mesh_terms: D000818:Animals; D001422:Bacterial Adhesion / Q000235:genetics; D002417:Cattle; D002460:Cell Line; D004196:Disease Outbreaks; D004847:Epithelial Cells / Q000382:microbiology; D004927:Escherichia coli Infections / Q000453:epidemiology / Q000235:genetics / Q000382:microbiology*; D019453:Escherichia coli O157 / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D008969:Molecular Sequence Data; D009656:North America / Q000453:epidemiology; D020411:Oligonucleotide Array Sequence Analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D022641:Shiga Toxin 2 / Q000235:genetics / Q000378:metabolism; D013045:Species Specificity; D014774:Virulence / Q000235:genetics
chemical_list: D029968:Escherichia coli Proteins; D022641:Shiga Toxin 2