Project Number: 5438-42000-014-07
Project Type: Trust

Start Date: Feb 01, 2012
End Date: Feb 28, 2013

Objective:
Characterization of carriage rates and types of non-O157 Shiga toxin-producing E. coli (STEC) in cattle from different production systems at harvest and determine if regional variations in non-O157 STEC serogroups exist.

Approach:
Sample collections will be made at numerous beef processing plants located across the United States in order to generate an extensive set of samples from the most relevant commercial sources. Targeted locations include California, Wisconsin, Nebraska, Texas, and Pennsylvania. Samples will consist of feces collected from colons during processing in order to have samples that reflect the production environment from which the animal originated. Processing plants that harvest fed cattle and cull cows and bulls from dairy and beef sources will be visited for sample collection. Feces will be screened before and after enrichment for the presence of STEC using a semi-quantitative molecular amplifiation method that detects the presence of Shiga toxin genes. This will not only identify cattle that carry STEC but also identifying those that carry higher loads and provide an estimate of the level of STEC that is shed. Samples found positive for STEC will be subjected to culture isolation for the Top-6 serotypes as well as all other STEC serotypes. All STEC isolates will be serotyped and characterized for genes that are known to contribute to increased virulence. These genes are Shiga toxin 1 (stx1); Shiga toxin 2 (stx2); intimin (eae); EHEC hemolysin (ehx); non-locus of enterocyte effacement effector (nle) products: nleB, nleC, nleF and nleG-2; subA (the prototype Subtilase cytotoxin); chuA, (an outer membrane heme uptake protein); irp2, (an iron repressible protein carried in a high-pathogenicity island); saa (associated with pathogenic STEC adherence); and other type III secreted effectors of EHEC (espK, and Ibe).