Are super-shedder feedlot cattle really super?
The objective of this study was to determine the frequency and duration of super-shedding in cattle by enumerating Escherichia coli O157:H7 in feces and to compare lineage and pulsed-field gel electrophoresis (PFGE) subtypes from super- and low-shedders. E. coli O157:H7 was enumerated from fecal samples obtained from the rectums of 400 feedlot cattle. Super-shedding steers (N=11) were identified, transported, and penned individually. Freshly voided fecal pats were sampled 2 h before and 6 h after feeding for 7 d, then once daily for an additional 19 d. Isolates (N=126) were subtyped using PFGE, and lineage was typed using a lineage-specific polymorphism assay. Of the 11 super-shedders identified at the commercial feedlot, only five were confirmed as super-shedders at the research feedlot, with no super-shedders identified 6 d after sampling at the commercial feedlot. Super-shedding was not consistent in fecal pats collected from the same individual at different times of the day. Isolates exhibited three distinct PFGE subtypes, with most isolates (97.6%) displaying the same subtype, including those obtained from steers that transitioned from super- to low-shedding. The short duration of super-shedding and its lack of continuance suggest that these individuals may not play as great a role in the dissemination of E. coli O157:H7 within the feedlot as previously proposed.
1 Agriculture and Agri-Food Canada, Lethbridge Research Centre , Lethbridge, Alberta, Canada .
Krysty D
KD
Munns
Lorna
L
Selinger
Kim
K
Stanford
L Brent
LB
Selinger
Tim A
TA
McAllister
D000416:Alberta / Q000453:epidemiology; D000822:Animal Husbandry; D000818:Animals; D057138:Bacterial Shedding; D002417:Cattle; D002418:Cattle Diseases / Q000382:microbiology* / Q000635:transmission; D015169:Colony Count, Microbial / Q000662:veterinary; D016521:Electrophoresis, Gel, Pulsed-Field / Q000662:veterinary; D004927:Escherichia coli Infections / Q000382:microbiology / Q000635:transmission / Q000662:veterinary*; D019453:Escherichia coli O157 / Q000145:classification / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D005243:Feces / Q000382:microbiology; D005838:Genotype; D008297:Male; D012007:Rectum / Q000382:microbiology; D013997:Time Factors