BACTERIOPHAGES (PHAGES) ARE BEING CONSIDERED AS AN ALTERNATIVE TOOL TO ANTIMICROBIAL DRUGS FOR TREATING BACTERIAL INFECTIONS IN MAN AND ANIMALS. OF DISEASES AFFECTING CATTLE IN THE U.S. BEEF FEEDLOT PRODUCTION SYSTEMS, LIVER ABSCESSES CAUSED BY FUSOBACTERIUM NECROPHORUM SUBSP. NECROPHORUM ARE A SIGNIFICANT CONCERN FOR ANIMAL HEALTH AND WELFARE AND PRODUCTION ECONOMICS. AVAILABLE EFFICACIOUS TREATMENTS ARE LIMITED TO ANTIMICROBIAL DRUGS, CURRENTLY THE MACROLIDE TYLOSIN AND TETRACYCLINES. MACROLIDES ARE RANKED BY THE WORLD HEALTH ORGANIZATION AS CRITICALLY IMPORTANT FOR HUMAN THERAPEUTIC OPTIONS AND WITH HIGHEST RISKS OF BACTERIAL RESISTANCE. AN EFFICACIOUS AND ECONOMICALLY SOUND ALTERNATIVE TO TYLOSIN COULD ENABLE THE INDUSTRY TO REDUCE OR ELIMINATE USE OF THIS CRITICALLY IMPORTANT DRUG CLASS, WHILE STILL ENSURING CATTLE HEALTH AND WELFARE. THIS PATHOGEN IS AN ANAEROBIC BACTERIAL SUBSP., AND PHAGES OF ANAEROBIC BACTERIA HAVE BEEN STUDIED THE LEAST. WHILE THERE ARE REPORTS OF ISOLATIONOF PHAGES OF F. NECROPHORUM FROM CATTLE RUMEN FLUIDS AND CITY SEWAGE IN OTHER COUNTRIES, EFFICACY OF THE PHAGES FOR PREVENTING OR REDUCING LIVER ABSCESSES CAUSED BY THE PATHOGEN HAS NOT BEEN STUDIED. IN THIS PROJECT, FREQUENCY OF ISOLATION OF PHAGES OF F. NECROPHORUM FROM RUMEN FLUIDS OF BEEF FEEDLOT CATTLE RAISED IN THE U.S. WILL BE ESTIMATED. THE PHAGES WILL BE DESCRIBED IN TERMS OF THEIR TAXONOMY, GENOMIC COMPOSITION, AND PATHOGEN STRAIN HOST-RANGE. AS WELL, DISTRIBUTION OF THE PHAGES IN A MAMMALIAN HOST AND THEIR POTENTIAL TO PREVENT OR REDUCE LIVER ABSCESSES CAUSED BY F. NECROPHORUM WILL BE TESTED IN A MOUSE MODEL OF THE DISEASE. THESE PROOF-OF-CONCEPT STUDIES WILL PROVIDE AN EVALUATION OF PHAGES AS AN ALTERNATIVE TOOL TO ANTIMICROBIAL DRUGS FOR THE DISEASE CONTROL. SUCH AN ALTERNATIVE WOULD SUPPORT LONG-TERM INDUSTRY SUSTAINABILITY AND CONTRIBUTE TO WIDER SOCIETAL EFFORTS TO PREVENT ANTIMICROBIAL RESISTANCE IN BACTERIAL PATHOGENS OF MAN AND ANIMALS.