Evaluation of a model for Escherichia coli O157:H7 colonization in streptomycin-treated adult cattle.
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.
Snider
Timothy A
TA
Department of Veterinary Pathobiology, Center for Veterinary Health Sciences, Oklahoma State University, Stillwater, OK 74078, USA.
Fabich
Andrew J
AJ
Washburn
Kevin E
KE
Sims
Will P
WP
Blair
Jeffrey L
JL
Cohen
Paul S
PS
Conway
Tyrrell
T
Clinkenbeard
Kenneth D
KD
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
D013307:Streptomycin