title: Use of model super-shedders to define the role of pen floor and hide contamination in the transmission of Escherichia coli O157:H7.
abstract: Super-shedders, cattle shedding at least 10(4) cfu of Escherichia coli O157:H7 per gram of feces, increase the risks of contaminating the food chain and disseminating the organism through cattle populations. Because detecting super-shedders in cattle populations is laborious and time-consuming, a study was conducted to evaluate the role of hide and pen-floor contamination by model super shedders (MSS) in transmission of E. coli O157:H7. Steers (n = 48) negative for E. coli O157:H7 were allocated to 6 pens, with 2 replicate pens per treatment. Treatment A consisted of 3,000 g of feces inoculated with 10(6) cfu/g of a 5-strain mixture of nalidixic acid-resistant E. coli O157:H7 and spread in simulated fecal pats on the pen floor for d 0 through 4 and d 14 through 18. For treatment B, 100 g of the feces per day was spread on the perineum of 1 MSS per pen, and the remaining feces was placed on the pen floor as fecal pats similar to treatment A. Treatment C differed from B in that 50 g of feces was spread on the perineum and 50 g on the brisket of the MSS steer. Fecal samples, perineal swabs (500-cm(2) area around the anus), freshly voided fecal pats and manila rope samples were collected during a 56-d experimental period. More positive rope samples were found in treatments B and C compared with A (P = 0.05), and steers within treatments B and C were 1.3 times more likely (P = 0.05) to shed E. coli O157:H7 in their feces than steers in treatment A. Even though the number of E. coli O157:H7 introduced into pens was similar, results indicate an increased importance of hide compared with pen-floor contamination for transmission of this organism to cattle. Because cattle within treatment B were persistently colonized with E. coli O157:H7, this design should prove suitable for future studies investigating the role of super-shedders in the transmission of E. coli O157:H7.
authors.affiliation: Alberta Agriculture and Rural Development, Agriculture Centre, 100, 5401-1st Avenue South, Lethbridge, Alberta, Canada T1J 4V6. kim.stanford@gov.ab.ca
authors.forename: K
authors.initials: K
authors.lastname: Stanford
authors.forename: T P
authors.initials: TP
authors.lastname: Stephens
authors.forename: T A
authors.initials: TA
authors.lastname: McAllister
mesh_terms: D000818:Animals; D057138:Bacterial Shedding / Q000502:physiology*; D002417:Cattle; D004927:Escherichia coli Infections / Q000382:microbiology / Q000635:transmission / Q000662:veterinary*; D019453:Escherichia coli O157 / Q000502:physiology*; D005243:Feces / Q000382:microbiology; D005430:Floors and Floorcoverings; D006799:Housing, Animal; D008297:Male; D016017:Odds Ratio; D010502:Perineum; D012867:Skin / Q000382:microbiology*; D013995:Time