The long-term goal of the project is to develop non-antibiotic pre-harvest interventions to remove or reduce foodborne bacterial pathogens in food animals. The hypothesis is that a novel treatment utilizing special viruses called bacteriophages, combined with traditonal treatments such as vaccination and probiotics, will further reduce the pathogen load in food animals without the use of antibiotics.
The primary objectives include (1) isolating and characterizing lytic bacteriophages that target food-borne bacterial pathogens, including E. coli O157:H7 and Salmonella serotypes; (2) developing bacteriophage delivery approaches for chickens and cattle; (3) determining the affect of bacteriophage treatment on pathogen shedding and severity of animal disease; (4) combining bacteriophage treatment with traditional intervention methods such as vaccination and probiotic treatment to further reduce pathogen shedding; and (5) examining the effect of antibiotic treatment or co-infection with a non-food-borne pathogen on shedding of a food-borne pathogen. <P>
Expected outputs from the project include pathogen-targeted bacteriophage mixtures that could be used by food animal producers as an alternative to antibiotic prophylaxis/treatment. In addition, veterinary students who work on this project will be trained in the field of pre-harvest food safety.
NON-TECHNICAL SUMMARY: Reducing human foodborne illness in the U.S. is a national priority. Food animals such as cattle and chickens are a major source of foodborne pathogens like Salmonella and E. coli O157:H7. These pathogens move to humans via contaminated food. This project addresses pathogen reduction in the live food animal, the necessary first step in the larger, integrated approach to removing pathogens from "farm to fork". The challenge has been to accomplish this "pre-harvest" intervention while at the same time decreasing producer reliance on antibiotic treatment of food animals. Therefore, our approach will be to combine a novel treatment utilizing special viruses called bacteriophages with traditonal treatments such as vaccination and probiotics to further reduce the pathogen load in food animals without the use of antibiotics. Bacteriophages are viruses that infect only bacteria; phages that kill Salmonella and E. coli O157:H7 will be isolated and used in this combined treatment approach. The overall impact of the work will be to make the food supply safer for human consumption. In addition, the decrease reliance on antibiotics that this approach allows will, in turn, decrease antibiotic resistance in pathogens that move from animals into humans. <P>
APPROACH: Bacteriophages will be isolated from a variety of sources, but primarily from enrichment cultures of specimens submitted to the AU-CVM teaching hospital. Each phage isolate will be screened on a panel of E. coli or Salmonella strains to determine its bacterial host range. Electron microscopy will be used to speciate phages. Several methods will be used to develop a phage delivery system, including the incorporation of phage mixtures into drinking water, food, and microspheres. Mixtures of bacteriophages will be given orally to experimentally infected animals, and the fecal colony counts of E. coli O157:H7 or Salmonella spp. will be observed and compared to the counts from non-infected animals. Bacteriophage treatment effect(s) on Salmonella disease in experimentally infected animals will be measured by scoring feces (dry/formed versus liquid/diarrhea) and measuring change in animal temperature compared to uninfected control animals. Changes in pathogen shedding by combining treatment protocols, or caused by treatment with antibiotics, or resulting from concurrent infection with another pathogen, will be measured by enumerating colony counts from fecal samples of treated, infected animals and comparing them with colony counts from non-treated, infected animals.