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United States Department of Agriculture

Agricultural Research Service

Research Project: Molecular Biology of Human Pathogens Associated with Food

Location: Produce Safety and Microbiology Research

Title: Insights into Evolution of Escherichia coli O157:H7 from Complete Genome Sequence of Closely Related O55:H7 Precursor

Authors
item Kyle, Jennifer
item Parker, Craig
item Cummings, Craig -
item Huynh, Steven
item Degorocija, Lovorka -
item Vatta, Paolo -
item Newton, Elizabeth -
item Petrauskene, Olga -
item Barker, Melissa -
item Tebbs, Robert -
item Fang, Rixun -
item Furtado, Monohar -
item Mandrell, Robert

Research conducted cooperatively with:
item

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 24, 2011
Publication Date: N/A

Interpretive Summary: leading cause of infant mortality and morbidity in developing countries. The EPEC O55:H7 serotype has been established as a recent precursor to the virulent, food-borne enterohemorrhagic E. coli serotype O157:H7. We determined the DNA sequence a DEC5 clone of O55:H7 to help elucidate the close evolutionary relationship to the O157:H7 serotype. We utilized two state of the art second generation sequencing technologies were used to ensure complete and accurate DNA sequencing. The EPEC O55:H7 genome is approximately 5.3 million base pairs and includes five plasmids. Three plasmids show similarity to those sequenced from other EPEC strains; the remaining two appear to be small, cryptic plasmids. A total of 18 prophage or integrated virus elements were identified, including 16 shared with the previously completed EPEC O55:H7 strain CB9615. The overall pattern of bacteriophage insertion elements appears genetically intermediate between the previously sequenced O157:H7 and O55:H7 strains. Thus, analysis of the complete sequence of this clone permits further insight into the evolution and emergence of the deadly O157:H7 serotype.

Technical Abstract: Enteropathogenic Escherichia coli (EPEC) is a leading cause of infant mortality and morbidity in developing countries. In spite of this, only two EPEC genomes have been fully sequenced: the typical, model EPEC strain E2348/69 (O127:H6), and the contemporary, atypical EPEC strain CB9615 (O55:H7, Germany, 2003). This latter serotype has been established as a recent precursor to the virulent, enterohemorrhagic E. coli serotype O157:H7. We chose to sequence a strain, RM12579, isolated in 1974 from a patient in California due to its spatial and temporal proximity to the first identified EHEC O157:H7 strain from 1975. Methods Multiple second generation sequencing technologies were used to ensure complete and accurate coverage. The long reads from 454 Sequencing™ at 33X coverage yielded an initial assembly that was further refined by high fidelity SOLiD™ system reads at 730X coverage. The remaining gaps in repetitive regions were filled by PCR and Sanger sequencing. Results The RM12579 genome is approximately 5.3 million base pairs, not including five plasmids. Three plasmids show similarity to those sequenced from other EPEC strains; the remaining two appear to be small, cryptic plasmids. A total of 18 prophage elements were identified, including 16 shared with the previously completed O55:H7 strain CB9615. Conclusions The overall pattern of phage insertion elements appears intermediate between the previously sequenced O157:H7 and O55:H7 strains. Thus, analysis of the complete sequence of this RM12579 strain permits further insight into the evolution and emergence of the deadly O157:H7 serotype.

Last Modified: 9/22/2014
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