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Title: ASSOCIATION OF SPECIFIC PER AND FLHD ALLELES IN ESCHERICHIA COLI O157:H7 WITH SORBITOL FERMENTATION

Author
item Bono, James - Jim
item Keen, James
item Laegreid, William

Submitted to: American Society of Microbiologists Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 2/17/2006
Publication Date: 5/1/2006
Citation: Bono, J.L., Keen, J.E., Laegreid, W.W. 2006. Association of specific per and flhd alleles in Escherichia coli O157:H7 with sorbitol fermentation [abstract]. American Society of Microbiologists. Poster No. C-056.

Interpretive Summary:

Technical Abstract: Enterohemorrhagic Escherichia coli (EHEC) O157 cause disease in humans via ingestion of contaminated food or water or contact with infected animals or people. Disease manifestations include hemorrhagic colitis and hemolytic uremic syndrome. EHEC O157 can be divided into two major subgroups, sorbitol non-fermenting (SNF) E. coli O157:H7/NM and sorbitol fermenting (SF) E. coli O157:NM. Each subgroup is epidemiologically, phenotypically and genetically different. In order to identify specific genotypic markers of these two major EHEC O157 subgroups, the per gene in the rfb O-antigen locus and the flhD gene in the flagellar master control operon, flhDC, were sequenced from five SF and SNF E. coli O157 isolates. These two operons were targeted because (1) preliminary sequencing of the E. coli O157 O-antigen operon identified a single nucleotide polymorphism (SNP) that associated with NSF and SF E. coli O157 isolates (Bono et al, unpublished) and (2) previous research demonstrated an association of a 12 bp deletion in the flhDC operon with SF E. coli O157:NM isolates (Monday, S. R., S. A. Minnich, and P. C. H. Feng. 2004. J Bacteriol. 168(6):2319-2327). We hypothesized SNP existence in NSF and SF E. coli O157 populations in one or both of these operons that would associate with sorbitol fermentating E. coli O157 isolates. We identified SNPs in both genes, per-sp11 and flhD-sp1, that defined two alleles, with NSF E. coli O157:H7:NM isolates bearing the A allele and SF E. coli O157:NM isolates bearing the B allele. Real-time PCR genotyping assays were designed against these two SNPs and tested against an additional diverse set of 315 SNF E. coli O157:H7 and 26 SF E. coli O157:NM isolates. With both the per-sp11 and flhC-sp1 assays, 26/26 SF E. coli O157:NM isolates had allele B (sensitivity 100%; 95% CI, 86.8 to 100) while only 1/315 and 3/315 of NSF E. coli O157:H7 possessed the B allele (specificity 99.7%; 95% CI, 98.3 to 99.9; 99.1%; 95% CI, 97.3 to 99.8, respectively). These results suggest that both the per-sp11 and flhC-sp1 SNPs are excellent targets for real-time PCR assays to discriminate SF E. coli O157:NM isolates from NSF E. coli O157:H7.