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United States Department of Agriculture

Agricultural Research Service

Research Project: PREVENTION AND CHARACTERIZATION OF PERSISTENT COLONIZATION BY E. COLI O157:H7 AND OTHER SHIGA TOXIN-PRODUCING E. COLI (STEC) IN CATTLE Title: Comparative genomic and phenotypic characterization of super-shedder Escherichia coli O157:H7

Authors
item Katani, Robab -
item Cote, Rebecca -
item Moreau, Mathew -
item Kudva, Indira
item Brandl, Maria
item Carter, Michelle
item Arthur, Terrance
item Debroy, Chitrita -

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: February 21, 2014
Publication Date: N/A

Technical Abstract: Shiga toxin-producing Escherichia coli O157:H7 (O157) are the cause of considerable morbidity and mortality worldwide. The pathogen is harbored in the terminal recto-anal junction (RAJ) of the intestinal tract of asymptomatic cattle, and is typically shed at 10 to 100 CFU/g of feces. Occasionally, “super-shedder” (SS) cattle excrete these bacteria in exceptionally large numbers (greater than or equal to 104 CFU/g of feces), and these individuals are thought to be major contributors to the persistence and spread of these pathogens on the farm and through the food production chain. Since the molecular mechanisms contributing to the super-shedding in cattle are unknown, we fully sequenced the genome of a strain of O157 recovered from SS cattle. Whole genome shotgun sequencing was used to obtain a high quality (greater than 100X coverage) scaffold of the genome of isolate SS17, and the genome was closed using a primer walking strategy. Automated (using RAST) and manual annotation was used to identify genes and other genomic features, and comprehensive comparative genomic analyses of SS17 with previously characterized reference E. coli genomes performed. The results show that SS17 has a genome size of slightly over 5.5Mb, and includes two plasmids, pO157 and pSS17 of 95, and 37 kb, respectively. Phylogenetic analyses also suggest that while SS17 appears genetically distinctive, it clusters with the LSPA lineage I/II genotype and previously described “spinach” outbreak strains. The adherence patterns of SS17 and other SS isolates to bovine RAJ squamous epithelium (RSE) cells was examined, and revealed that SS isolates manifest a unique strong aggregative adherence pattern on bovine RSE cells as compared with reference isolates. In addition, SS17 appeared to better attach and colonize to the surfaces of green leafy vegetables. Together, these results suggest that SS17 and other O157 isolates from SS cattle may harbor unique genomic and microbiologic features that may play a role in the super-shedding phenotype.

Last Modified: 8/1/2014
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