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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: E. coli serotype O55:H7 diversity supports parallel acquisition of bacteriophage at Shiga toxin phage insertion sites during evolution of the O157:H7 lineage

item Kyle, Jennifer
item Cummings, Craig
item Parker, Craig
item Quiñones, Beatriz
item Vatta, Paolo
item Newton, Elizabeth
item Huynh, Steven
item Swimley, Michelle
item Degoricija, Lovorka
item Barker, Melissa
item Walker, Samarpita
item Nguyen, Kimberly
item Patel, Ronak
item Fang, Rixun
item Tebbs, Robert
item Petrauskene, Olga
item Furtado, Manohar
item Mandrell, Robert

Submitted to: Journal of Bacteriology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/27/2012
Publication Date: 3/28/2012
Publication URL:
Citation: Kyle, J.L., Cummings, C.A., Parker, C., Quinones, B., Vatta, P., Newton, E., Huynh, S., Swimley, M.S., Degoricija, L., Barker, M., Fontanoz, S., Nguyen, K.M., Patel, R.N., Fang, R., Tebbs, R., Petrauskene, O., Furtado, M., Mandrell, R.E. 2012. E. coli serotype O55:H7 diversity supports parallel acquisition of bacteriophage at Shiga toxin phage insertion sites during evolution of the O157:H7 lineage. Journal of Bacteriology. 194:1885-1896.

Interpretive Summary: Enteropathogenic Escherichia coli (EPEC) is a 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 RM12579 an O55:H7 strain from a California 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: Insights into Evolution of Escherichia coli O157:H7 from Complete Genome Sequence of Closely Related O55:H7 Precursor Enteropathogenic Escherichia coli (EPEC) continues to be a leading cause of mortality and morbidity in children around the world. The O55:H7 serotype is a recent precursor to the virulent enterohemorrhagic E. coli (EHEC) serotype O157:H7. To explore this diversity, we fully sequenced EPEC O55:H7 str. RM12579 from California, collected one year before the first US isolate of O157:H7 was identified in 1975 in California. The RM12579 chromosome was 5,263,980 bp and possessed five plasmids, two of which encoded resistance to ampicillin and streptomycin antibiotics. Phage-related sequences accounted for nearly all differences between the two fully sequenced O55:H7 strains. Mobile genomic islands encode the majority of virulence factors in pathogenic E. coli, and we also examined the genetic diversity of 14 other O55:H7 by testing for key virulence genes. Additionally, O55:H7 and O157:H7 strains were tested for the presence and insertion site of Shiga toxin gene (stx)-containing bacteriophages. Although separate analysis of non-phage-associated genes supported core elements of previous O157:H7 evolutionary models, phage composition and insertion analyses suggested a key refinement. Specifically, the placement and presence of stx-containing bacteriophages should not be considered a stable evolutionary marker, nor a requirement for placing O55:H7 and O157:H7 strains within the stepwise evolutionary model. Exploration of O55:H7 diversity improved our understanding of the evolution of the E. coli O157:H7 pathogen, and further suggested that new configurations of stx-containing E. coli will continue to appear in the future.

Last Modified: 10/16/2017
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