ARS | Publication request: PCR Analysis of Pathogenic E. coli on Three Dairy Farms in the Northeastern United States

Submitted to: Joint Abstracts of the American Dairy Science and Society of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: February 23, 2009
Publication Date: July 14, 2009
Citation: Karns, J.S., Van Kessel, J.S. 2009. PCR Analysis of Pathogenic E. coli on Three Dairy Farms in the Northeastern United States. Joint Abstracts of the American Dairy Science and Society of Animal Science. J. Anim. Sci. Vol. 87, E-Suppl. 2/J. Dairy Sci. Vol. 92, E-Suppl. 1

Technical Abstract: Cattle are considered a significant reservoir of pathogenic Escherichia coli that cause food borne illness in humans. The association of enterohemorrhagic E. coli O157:H7 with beef cattle is well known but less is known about the occurrence of this organism in dairy cattle. In this study real-time PCR assays were used to detect virulence genes associated with pathogenic forms of E. coli in feces and environmental samples collected bi-annually from three dairy farms in the northeast US over a 3-year period. The eaeA gene encoding intimin was detected in the feces of 79 percent (range 54-97 percent), 73 percent (54-89 percent), and 92 percent (75-100 percent) of the cows on Farms A, B, and C, respectively. The gamma allele of the translocated intimin receptor (g-tir), that is associated with O157:H7 was detected in 28 percent (6-64 percent), 28 percent (2-58 percent), and 42 percent (3-90 percent) of the fecal samples from the respective farms. The stx1 and stx2 genes encoding shiga-like toxins were found less frequently in fecal samples from Farm A (stx1 47 percent [22-77 percent]; stx2 37 percent [25-57 percent]) than in those from Farm B (stx1 68 percent [53-84 percent]; stx2 69 percent [52-79 percent]) or Farm C (stx1 63 percent [39-88 percent]; stx2 62 percent [32-74 percent]). The combination of virulence factors suggestive of the presence of O157:H7 (eaeA+, g-tir+, stx2+, stx1+or -) was found in numerous samples from Farms B and C but O157:H7 was isolated from few fecal samples and only from environmental manure samples associated with young animals. O157:H7 did not seem to persist in individual animals as cows which yielded positive samples at one sample time tested negative for this organism in subsequent samplings. These results suggest that E. coli O157:H7 is somewhat rare on these dairy farms but that other types of shiga-toxin-producing E. coli are more frequent and may present risks to the public.