Submitted to: International Symposium and Workshop on Shiga Toxin ... Escherichia coli
Publication Type: Abstract Only
Publication Acceptance Date: 2/28/2003
Publication Date: 6/9/2003
Citation: LAEGREID, W.W., BONO, J.L., CLAWSON, M.L., KEEN, J.E. SEQUENCE DIVERSITY OF ESCHERICHIA COLI O157:H7 ISOLATES. INTERNATIONAL SYMPOSIUM AND WORKSHOP ON SHIGA TOXIN ... ESCHERICHIA COLI. 2003. Abstract p. 137. Interpretive Summary:
Technical Abstract: Much of the evolution, virulence and other properties of shiga toxin-producing E. coli (STEC) O157:H7 are the result of acquisition of specific sets of genes through lateral transfer. However, nucleotide sequence variation in those genes, as well as other genes more broadly distributed amongst E. coli, contributes to phenotypic variation within EHEC O157:H7. To estimate the extent of sequence variation in EHEC O157:H7, a set of 11 genes were randomly selected from the K-12 genome and sequenced in 24 EHEC O157:H7 isolates. The panel included human clinical isolates, food isolates and bovine field isolates, as well as K-12. In addition to randomly selected genes, a set of genes that might be expected to be under some external selective pressure, including outer membrane, receptor, flagellar and virulence genes, were also sequenced. A high degree of sequence homology was detected in randomly selected genes with less than 0.04% sequence divergence within EHEC O157:H7 isolates and an average of 0.97% divergence from K-12. As expected, genes expected to be under some selection had higher divergence, 0.22% within EHEC O157:H7 and 8.0% compared to K-12. These results support previous findings of the highly clonal nature of EHEC O157:H7 but also indicate the presence of single nucleotide polymorphisms within genes associated with virulence or other properties of these bacteria. The functional significance of these polymorphisms remains to be determined.