Are super-shedder feedlot cattle really super?

Area of Science:

• Veterinary Microbiology
• Food Safety
• Animal Science

Background:

• Escherichia coli O157:H7 (E. coli O157:H7) is a significant foodborne pathogen.
• Cattle are a primary reservoir for E. coli O157:H7, with super-shedding potentially contributing to pathogen dissemination.

Purpose of the Study:

• To determine the frequency and duration of E. coli O157:H7 super-shedding in feedlot cattle.
• To compare E. coli O157:H7 lineage and pulsed-field gel electrophoresis (PFGE) subtypes between super- and low-shedders.

Main Methods:

• Enumerated E. coli O157:H7 in fecal samples from 400 feedlot cattle.
• Identified and individually penned 11 super-shedding steers for intensive fecal sampling over 26 days.
• Subtyped isolates using PFGE and lineage-specific assays.

Main Results:

• Only five of the 11 identified super-shedders were confirmed at a research facility.
• Super-shedding was not consistently observed in samples from the same animal on different days or times.
• Most isolates (97.6%) belonged to a single PFGE subtype, even in steers transitioning between shedding levels.

Conclusions:

• Super-shedding of E. coli O157:H7 in cattle appears to be of short duration and inconsistent.
• The limited and inconsistent nature of super-shedding suggests these animals may have a lesser role in feedlot pathogen dissemination than previously thought.