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Applied and Environmental Microbiology, September 2009, p. 5927-5937, Vol. 75, No. 18
0099-2240/09/$08.00+0     doi:10.1128/AEM.00972-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Escherichia coli O157:H7 Strains That Persist in Feedlot Cattle Are Genetically Related and Demonstrate an Enhanced Ability To Adhere to Intestinal Epithelial Cells {triangledown}

Brandon A. Carlson,1 Kendra K. Nightingale,1 Gary L. Mason,2 John R. Ruby,3 W. Travis Choat,4 Guy H. Loneragan,5 Gary C. Smith,1 John N. Sofos,1 and Keith E. Belk1*

Center for Meat Safety & Quality, Department of Animal Sciences, Colorado State University, Fort Collins, Colorado 80523-1171,1 Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado 80523-1619,2 JBS Packerland Inc., Green Bay, Wisconsin 54311,3 Elanco Animal Health, Greenfield, Indiana 46140,4 Feedlot Research Group, West Texas A&M University, Canyon, Texas 79016-00015

Received 28 April 2009/ Accepted 10 July 2009

A longitudinal study was conducted to investigate the nature of Escherichia coli O157:H7 colonization of feedlot cattle over the final 100 to 110 days of finishing. Rectal fecal grab samples were collected from an initial sample population of 788 steers every 20 to 22 days and microbiologically analyzed to detect E. coli O157:H7. The identities of presumptive colonies were confirmed using a multiplex PCR assay that screened for gene fragments unique to E. coli O157:H7 (rfbE and fliCh7) and other key virulence genes (eae, stx1, and stx2). Animals were classified as having persistent shedding (PS), transient shedding (TS), or nonshedding (NS) status if they consecutively shed the same E. coli O157:H7 genotype (based on the multiplex PCR profile), exhibited variable E. coli O157 shedding, or never shed morphologically typical E. coli O157, respectively. Overall, 1.0% and 1.4% of steers were classified as PS and NS animals, respectively. Characterization of 132 E. coli O157:H7 isolates from PS and TS animals by pulsed-field gel electrophoresis (PFGE) typing yielded 32 unique PFGE types. One predominant PFGE type accounted for 53% of all isolates characterized and persisted in cattle throughout the study. Isolates belonging to this predominant and persistent PFGE type demonstrated an enhanced (P < 0.0001) ability to adhere to Caco-2 human intestinal epithelial cells compared to isolates belonging to less common PFGE types but exhibited equal virulence expression. Interestingly, the attachment efficacy decreased as the genetic divergence from the predominant and persistent subtype increased. Our data support the hypothesis that certain E. coli O157:H7 strains persist in feedlot cattle, which may be partially explained by an enhanced ability to colonize the intestinal epithelium.

* Corresponding author. Mailing address: Center for Meat Safety & Quality, Department of Animal Sciences, Colorado State University, 7C Animal Sciences, Ft. Collins, CO 80523-1171. Phone: (970) 491-5826. Fax: (970) 491-0278. E-mail: Keith.Belk{at}ColoState.edu

{triangledown} Published ahead of print on 17 July 2009.

Applied and Environmental Microbiology, September 2009, p. 5927-5937, Vol. 75, No. 18
0099-2240/09/$08.00+0     doi:10.1128/AEM.00972-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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