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United States Department of Agriculture

Agricultural Research Service

Research Project: DAIRY MANAGEMENT PRACTICES AND THE TRANSMISSION OF ZOONOTIC PATHOGENS IN MILK Title: Diversity of Escherichia Coli in a Dairy Farm

Authors
item Son, Insook
item Van Kessel, Jo Ann
item Karns, Jeffrey

Submitted to: BARC Poster Day
Publication Type: Abstract Only
Publication Acceptance Date: March 24, 2008
Publication Date: April 23, 2008
Citation: Son, I., Van Kessel, J.S., Karns, J.S. 2008. Diversity of escherichia coli in a dairy farm. April 23, 2008. BARC Poster Day .

Technical Abstract: Dairy cattle are known reservoirs of pathogenic E. coli, but little is known about the dynamics of E. coli in dairy cows or within the dairy farm environment. This study was conducted to determine the relationships between E. coli in water, feces, and manure composites from a dairy farm using pulsed field gel electrophoresis (PFGE) to discriminate E. coli strains. Water from four watering troughs, feces from fifteen cows, and manure composite samples from five sampling sites were collected on Dec., 2005 and Dec., 2006. E. coli isolates (n=530) from water (n=80), manure composites (n=150), and feces (n=300) were characterized by phenotypic testing and confirmed through gadAB-specific PCR. Isolates were analyzed for phylogenetic grouping (A, B1, B2, and D) using a triplex PCR method. Virulent E. coli strains primarily fall within the groups B2 and D. In this study, 5.8% and 10.4% of the isolates were within groups B2 and D, respectively. The remainder of the isolates were in the groups A (20.8%) and B1 (63%) indicating that most of these isolates were commensal E. coli. Real-time PCR analysis for the genes encoding the virulence factors shiga toxins (stx1and stx2), and intimin (eaeA) suggested that two isolates from one composite manure sample were enterohemorrhagic E. coli (EHEC). PCR analysis for the '-allele of the translocated intimin receptor and agglutination assays confirmed that these two isolates were E. coli O157:H7. PFGE analysis of XbaI-digested genomic DNA from E. coli isolates resulted in 171 unique restriction digestion patterns (RDPs) based upon cluster analysis using 100% Dice similarity in conjunction with unweighted pair group method with arithmetic mean. The E. coli isolates from water, manure composite, and fecal samples were clustered in 35 RDPs, 73 RDPs, and 87 RDPs, respectively. For fecal samples, cluster analysis generally showed that there was little diversity of isolates from individual cows, however high diversity was observed between animals. In general, there was more diversity within the water and composite samples than was observed in the fecal samples. Some RDPs were common to multiple sample types. Although there were common RDPs between the 2005 and 2006 samplings, the E. coli populations were overall quite distinct between these two sampling times. These results demonstrate a high degree of diversity for E. coli within a dairy farm and that, although it was detected on this farm, the frequency of O157:H7 colonization was very low.

Last Modified: 10/21/2014
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