title: Evaluation of a model for Escherichia coli O157:H7 colonization in streptomycin-treated adult cattle.
abstract: OBJECTIVE
  To develop a repeatable model for studying colonization with streptomycin-resistant Escherichia coli O157:H7 in adult cattle.
  
  
  METHODS
  5 adult mixed-breed beef cattle.
  
  
  METHODS
  Cattle were surgically cannulated in the duodenum, treated daily with streptomycin (33 mg/kg) via the duodenal cannula prior to and during experimental colonizations, and colonized with 10(10) CFUs of streptomycin-resistant E coli O157:H7 via the duodenal cannula. Colonization of rectal mucus and shedding in feces were monitored. Antimicrobials were administered to eliminate the colonizing strain so that 5 repeated colonization experiments could be performed. A comprehensive analysis of colonization was performed at necropsy.
  
  
  RESULTS
  Streptomycin treatment resulted in improved experimental colonization variables, compared with untreated controls, during initiation (days 2 to 6) and early maintenance (days 7 to 12) of colonization. Elimination of the colonizing strain followed by 5 repeated colonizations in the same animals indicated the repeatability of the protocol. Positive results of bacteriologic culture of feces 7 and 12 days after colonization were obtained in 100% and 84% of samples, respectively, across all animals and trials. At necropsy, highest magnitude recovery was in terminal rectal mucus.
  
  
  CONCLUSIONS
  The model was highly repeatable and novel with respect to streptomycin treatment, use of duodenal cannulas, and repeated colonizations of the same animals. Its use in adult cattle, from which most bovine-derived food originates, is critical to the study of preharvest food safety. The findings have implications for understanding intermittency of shedding in the field and for proposed vaccine-based interventions.
authors.affiliation: Department of Veterinary Pathobiology, Center for Veterinary Health Sciences, Oklahoma State University, Stillwater, OK 74078, USA.
authors.forename: Timothy A
authors.initials: TA
authors.lastname: Snider
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Fabich
authors.forename: Kevin E
authors.initials: KE
authors.lastname: Washburn
authors.forename: Will P
authors.initials: WP
authors.lastname: Sims
authors.forename: Jeffrey L
authors.initials: JL
authors.lastname: Blair
authors.forename: Paul S
authors.initials: PS
authors.lastname: Cohen
authors.forename: Tyrrell
authors.initials: T
authors.lastname: Conway
authors.forename: Kenneth D
authors.initials: KD
authors.lastname: Clinkenbeard
mesh_terms: D000818:Animals; D002404:Catheterization / Q000662:veterinary; D002417:Cattle; D002418:Cattle Diseases / Q000188:drug therapy / Q000382:microbiology*; D015169:Colony Count, Microbial / Q000662:veterinary; D004195:Disease Models, Animal; D004386:Duodenum / Q000382:microbiology; D004927:Escherichia coli Infections / Q000188:drug therapy / Q000662:veterinary*; D019453:Escherichia coli O157; D005243:Feces / Q000382:microbiology; D007413:Intestinal Mucosa / Q000382:microbiology; D013307:Streptomycin / Q000627:therapeutic use
chemical_list: D013307:Streptomycin