Factors That Influence Cattle Colonization with E. Coli O157:h7
E. coli O157:H7 (O157) is an important zoonotic pathogen estimated to cause more than 70,000 cases of human infection annually in the United States. The disease is characterized by bloody diarrhea and in 5 to 10% of the patients, a severe life-threatening sequel, the hemolytic uremic syndrome, results. The most important reservoir for O157 is healthy cattle, which carry O157 transiently and sporadically in their gastrointestinal tract. We do not understand how cattle become colonized with O157 or how they spontaneously clear the bacteria. It is well established however, that the prevalence of O157 carriage among cattle is greater in the summer than in the winter. O157 is transmitted to humans by ingestion of contaminated foodstuffs or water or by direct contact with cattle. Because healthy cattle are the source of human infection, practices that
reduce or eliminate O157 from cattle will significantly reduce illness in people. Such practices have not been established. In fact, just reducing the level of O157 carriage to the winter levels would have a significant positive effect. This proposal outlines experiments that will add to our basic understanding of the relationship between cattle and O157 and includes three objectives. First we will continue our ongoing work to analyze specific bacterial genes that contribute to the microbes' ability to efficiently colonize cattle by analyzing the effects of removing specific traits of O157. Second, we will use the power of DNA sequencing and genetic analysis to compare other, non-O157 E. coli (previously isolated and characterized in our laboratory) that also efficiently colonize the same unique bovine GI tract niche as O157. These comparisons may identify previously overlooked bacterial
traits that allow O157 to persist in cattle. Third, we will determine if seasonal variation in O157 carriage is due to intrinsic or extrinsic factors. This information will begin to solve the puzzle of seasonal variation in O157 carriage. The ultimate goal of this basic research is to contribute to our knowledge and to the development of science-based effective interventions to reduce or eliminate O157 from cattle. In turn, this will positively impact food safety and human health.