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U.S. Department of Health and Human Services

Animal & Veterinary

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STEC, Salmonella virulence and antibiotic resistance in cattle and feed

Principal Investigator: Dr. David Acheson
Organization: New England Medical Center


It has never been more important to ensure the microbiological safety of food, and while food in the United States is amongst the safest in the world, there are still many thousands of people developing a variety of foodborne illnesses on a daily basis in this country. The focus of this application is on two groups of important foodborne pathogens: Shiga toxin producing E. coli (STEC), e.g. E. coli 0157:H7, and Salmonella. The objectives are:

  1. To follow the epidemiology of STEC longitudinally in animal feed and then in cattle.
  2. To determine the prevalence of STEC isolates that carry virulence genes that are considered to be important in causing human disease and in what way these change longitudinally in the same animals.
  3. To determine the epidemiology of antimicrobial resistance phenotypically and genotypically in Salmonella and STEC as the organisms move longitudinally from feed into animals.
  4. To determine the genotypic and clonal characteristics of antibiotic resistant Salmonella and STEC.

We are collaborating with investigators at Kansas State University who will provide samples and isolates for our studies. We have two aims to address our objectives. First, we propose to isolate and characterize STEC of multiple serotypes from cattle and animal feed for known human virulence factors (Shiga toxin I or 2 expression, hemolysin, attachment to epithelial cells etc.). We will quantitate Stx expression and determine bacteriophage induction as well as characterize STEC by PFGE. Second, we propose to address another goal of the RFA, namely to investigate the fate and transmission dynamics of antibiotic resistance in human foodborne pathogens. This will be undertaken by documenting phenotypic and genotypic antibiotic resistance characteristics in STEC and Salmonella isolates, particularly in relation to extended spectrum b -lactamases and flouroquinolones. The long term goal of this application is to establish baseline data on the longitudinal epidemiology and clonality of two important foodborne pathogens, STEC and Salmonella. At the conclusion of the work we will have a better idea of the prevalence of pathogenic STEC in cattle and feed, and how these move from feed to animals and change in animals with time. We will also determine antibiotic resistance patterns on a cross-sectional and longitudinal basis in STEC and Salmonella.