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ARS Home » Plains Area » Clay Center, Nebraska » U.S. Meat Animal Research Center » Meat Safety and Quality » Research » Publications at this Location » Publication #371300

Research Project: Genomic and Metagenomic Differences in Foodborne Pathogens and Determination of Ecological Niches and Reservoirs

Location: Meat Safety and Quality

Title: Changes in a closed feedlot Escherchia coli O157:H7 population over 22 years

item Weinroth, Margaret - Maggie
item Clawson, Michael - Mike
item Arthur, Terrance
item Wells, James - Jim
item Harhay, Dayna
item Bono, James - Jim

Submitted to: Journal of Food Protection
Publication Type: Abstract Only
Publication Acceptance Date: 5/1/2020
Publication Date: 8/2/2020
Citation: Weinroth, M., Clawson, M., Arthur, T., Wells, J., Harhay, D., Bono, J. 2020. Changes in a closed feedlot Escherchia coli O157:H7 population over 22 years. [Abstract]. International Association for Food Protection Conference, Cleveland, Ohio, August 2-5 2020. Virtual. Journal of Food Protection. 83(Supplement A):P2-198.

Interpretive Summary:

Technical Abstract: Introduction: Shiga toxin-containing Escherichia coli O157:H7 (STEC O157:H7) is a naturally occurring pathogen in beef feedlots. Many epidemiology studies have tracked STEC O157:H7 populations in feedlots but typically for only a short period. To better understand how STEC O157:H7 populations change over time, we studied the genomes from strains isolated over 22 years. Purpose: The objective of this study was to characterize genetic variation of STEC O157:H7 in cattle from a closed feedlot over a 22-year period. Methods: From 1997 to 2019, STEC O157:H7 isolates were collected annually from the same feedlot and stored at -80°C. Up to 10 isolates per year were inoculated in TSB and grown overnight. DNA was extracted, libraries constructed, and sequenced on an Illumina NextSeq sequencing platform. Sequencing reads were assembled with SPAdes. Contigs from each isolate were typed for Shiga toxin subtype and tir (translocated intimin receptor) A/T variant and used to construct a phylogenetic tree with Parsnp along with previously sequenced strains for a total of 191 strains. Results: Phylogenetic analysis classified the strains into four clades that associated with tir A/T alleles and Shiga toxin subtypes. One clade had multiple Shiga toxin subtypes when compared to the three other more homologous clades. All four of the clades were present in strains isolated from 1997 through 2010 although not necessarily every year. Outside of one strain from a different clade, only strains from one of the four clades were isolated from 2011 to 2019. Significance: These data provide a first glimpse into the ecology of STEC O157:H7 in a natural environment and the evolutionary changes that have occurred over 22-years as it has adapted to this environment. Additionally, these data provide valuable information about strain relatedness that will help improve foodborne outbreak tracking.