Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/27/2006
Publication Date: 1/20/2007
Citation: Cornick, N.A., Helgerson, A.F., Sharma, V.K. 2007. Shiga toxin and shiga toxin-encoding phage do not facilitate E. coli O157:H7 colonization in sheep. Applied and Environmental Microbiology. 73(1):344-346. Interpretive Summary: Escherichia coli O157:H7 is the most frequent cause of bloody diarrhea in humans and has been associated with the most important foodborne outbreaks in the USA and Canada. Cattle and other ruminants are considered the major reservoir for E. coli O157:H7. Overwhelming amount evidence indicates that these bacteria colonize intestine of ruminants, which secrete these bacteria in feces. Understanding of factors that enable E. coli O157:H7 to colonize ruminant intestine will help develop strategies for reducing E. coli O157:H7 prevalence and shedding in these animals. The present study was designed to determine if Shiga toxins or the Shiga toxin encoding bacteriophage contribute to the ability of O157:H7 to colonize ruminant intestine using sheep as an animal model. When sheep were inoculated with O157:H7 strains either encoding Shiga toxin or lacking the ability to produce Shiga toxin, no significant effect was observed on the persistence of O157:H7 in sheep challenged with Shiga toxin-positive or Shiga toxin-negative strains. It was concluded from these results that Shiga toxin 2 did not contribute to persistence of E. coli O157:H7 in sheep.
Technical Abstract: Isogenic strains of E. coli O157:H7, missing either stx2 or the entire stx2 encoding phage, were compared with the parent strain for their ability to colonize sheep. The absence of the phage or of the Shiga toxin did not significantly impact the magnitude or duration of shedding of E. coli O157:H7.