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Comparison of Recto-anal Junction Mucosal Swab and Fecal
Culture for Detection of Escherichia coli O157:H7 in Dairy Heifers

Investigators
Bohach, Carolyn
Institutions
University of Idaho
Start date
2004
End date
2005
Objective
1. To determine the sensitivity of RAMS, researchers compared that method with fecal immunomagnetic separation (IMS).

2. To evaluate the ability of RAMS culture to predict duration of infection, the researchers also conducted a longitudinal study of natural E. coli O157:H7 infections among dairy heifers using 1) direct and enriched RAMS culture, 2) direct fecal culture and 3) IMS-enriched fecal culture.

More information
Findings: We tested the hypothesis that a new culture method for E. coli O157:H7 developed in our laboratory, could replace traditional fecal culture and predict long-term and short-term O157-shedding cattle. We conducted a year-long study of forty dairy heifers and compared the sensitivity of finding O157 in recto-anal mucosal swabs (RAMS) with finding it in fecal samples. Forty weaned heifers were studied and both fecal and RAMS samples were collected from each animal monthly for twelve months. Fecal samples were cultured by the standard and most sensitive methods known: direct plating and immunomagnetic separation enrichment IMS). RAMS samples were cultured by direct plating and enrichment. Direct fecal culture was the least sensitive method and missed many animals that were carrying E. coli O157:H7. RAMS enrichment was as sensitive as IMS fecal enrichment, was less costly, and yielded quantitative data. RAMS did not predict the duration of infection, as we had predicted. However, we found that the number of fecal E coli O157:H7 were associated with duration of infection, providing evidence for the existence of “super shedders”, or colonized animals that excrete high levels of E. coli O157:H7 in feces and are therefore responsible for a high proportion of environmental pathogen load.

For complete projects details, view the Project Summary.

Funding Source
Nat'l. Cattlemen's Beef Assoc.
Project number
BC-2004-3
Categories
Escherichia coli
Bacterial Pathogens