The existence of two separate lineages of Escherichia coli O157:H7 has previously been reported, and research indicates that one of these lineages (lineage I) might be more pathogenic toward human hosts. We postulated that the lineage more pathogenic expresses higher levels of
Shiga toxin 2 (Stx2) than do the nonpathogenic lineage II. A comprehensive set of methodologies were used to investigate the difference in Stx2 protein and mRNA expression between the two lineages. An initial Stx2-specific enzyme-linked immunosorbent assay was conducted, and lineage I overall
demonstrated significantly more toxin proteins expressed (P < 0.01). Gene expression analyses all showed significantly higher stx2 gene expression in lineage I (P < 0.02). PCR mapping revealed a possible explanation for decreased amounts of stx2
transcripts in the potentially nonpathogenic lineage II isolates, suggesting that genomic changes have modified the toxin-encoding region of the phage. This study provides additional data to support the existence of two diverse lineages of E. coli O157:H7, one of which may have lower
pathogenic potential in relation to human hosts. The PCR described also provides a possible screening tool for E. coli O157 populations to differentiate these lineages. This study provides useful information on the ecology of E. coli O157, with broad implications within the clinical,
scientific, and livestock industries.
Document Type: Research Article
U.S. Department of Agriculture, Agricultural Research Service Livestock Issues Research Unit, 1604 West FM 1294, Lubbock, Texas 79403, USA
Publication date: August 1, 2008
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