PREVENTION AND CONTROL OF SHIGA-TOXIGENIC ESCHERICHIA COLI IN LIVESTOCK
Location: Meat Safety & Quality Research
Title: Bacterial Communities Associated with Shiga-Toxigenic E. coli O157:H7 (STEC O157) in Beef Cattle Feedlot Environments
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: February 17, 2009
Publication Date: April 1, 2009
Citation: Durso, L.M., Harhay, G.P., Bono, J.L., Smith, T.P., Laegreid, W.W., Keen, J.E., Clawson, M.L. 2009. Bacterial Communities Associated with Shiga-Toxigenic E. coli O157:H7 (STEC O157) in Beef Cattle Feedlot Environments [abstract]. Microbial Ecology 57(3):569.
Background: The life cycle of Shiga-toxigenic E. coli O157:H7 (STEC O157) in beef cattle feedlots involves two habitats: the warm, nutrient rich primary habitat of the lower gastrointestinal tract of cattle and the generally cool, nutrient limiting secondary habitat outside of the animal, including the feedlot surface material. In both of these habitats, STEC O157 must interact with other microorganisms and compete for resources. We used 16S ribosomal RNA gene (16S rDNA) to characterize the bacteria present in the STEC O157:H7 primary and secondary habitats.
Methods: Fecal samples were collected from three STEC O157 culture-positive and three culture-negative beef cattle animals. All six animals were housed in the same pen and fed the same diet. Additionally, three feedlot surface material samples were collected from the pen in which the animals were housed. 16S rDNA was amplified using "universal" bacterial primers, cloned into TOPO4 vectors, and sequenced using an ABI 3730. Sequences were screened for chimeras using Bellepheron and aligned using a NAST alignment tool. DOTUR was used to generate rarefaction curves, and sequences were assigned taxonomies using the RDP classify tool and BLAST.
Results: Near full length 16S rDNA sequence was obtained for 14,944 clones from cattle feces and the corresponding feedlot pen surface material. Firmicutes were the predominant phylum in feces (54%), followed by the Bacteroidetes (40.5%) and Proteobacteria (5.5%). The predominant phylum in the feedlot surface material was Actinobacteria (42%), followed by Firmicutes (24%), Bacteroidetes (24%), and Proteobacteria (9%). There were 139 genera identified in the STEC O157 primary and secondary habitats, 25 of which were present in both habitats. Eleven genera had different frequencies of occurrence in STEC O157 culture-positive and -negative cattle.
Conclusion: Our results demonstrate 1) there are differences in the microbial frequencies between STEC O157 culture-positive and -negative animals and 2) while feces may be the source of much of the mass of the feedlot surface material, the microbial profile of the feces and that of the feedlot pen differ greatly.