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.

Association of Cell-adhesion Activities with Virulence in Shiga toxin-producing <i>Escherichia coli</i> O103：H2

“…Adhesion genes iha and saa and the genes coding enzymes that assist in the colonization of STEC espP, katP, and stcE were sporadically possessed. However, the prevalence of these genes was not correlated with the level of symptom and the cell-adhesion activity Table 1 . On the other hand, it has been reported that there is variation in the expression of the genes on LEE among STEC O157 strains with differing cell-adhesion activity Abu-Ali et al, 2010Tobe et al, 2005 . Accordingly, we next analyzed the expression of these genes eae, espB, espD, and tir among six strains ESC531, ESC574, ESC552, ESC553, ESC554, ESC569 .…”

“…First, we examined the variations in adhesion activity to Caco-2 cells among the strains. Abu-Ali et al Abu-Ali et al, 2010 showed differences in the level of adhesion to epithelial duplicate for every sample. The amplifications of eae and 16S rRNA gene were performed with the primers previously described Bergholz et al, 2007 Nielsen andAndersen, 2003 .…”

Virulence genes of Shiga toxin-producing Escherichia coli O157:H7 strains isolated from calves and cattle

“…It has been reported that cattle are main reservoir for STEC (2,20,26). Investigations carried out in different part of Europe, Asia, North America have showed that 10-80% cattle were infected with STEC (1,2,5,8,27,39). The occurrence of E.coli O157:H7 were also detected in different regions of Turkey.…”

“…The pathogenicity of STEC O157:H7 is associated with a number of virulence factors, including Shiga toxins 1 and 2, as well as intimin and enterohaemolysin (1,2,6,8,27,31,37). Kang et al (19) reported that stx(1) and stx(2) appear to play a major role in the pathogenesis of haemorrhagic colitis and haemolyticuremic syndrome and STEC strains predominantly carries either stx(1) or stx(2) or both genes.…”

“…E. coli O157:H7 produced verotoxins are very similar to cytotoxins called stxs. However, stx (1) and stx (2) are encoded by different sets of genes. Therefore, stx(1) and stx (2) are different proteins but their active molecular structure and biological functions are identical to the other Shiga toxins (23).…”