Isolation and Use of Bacteriophage to Reduce Escherichia coli O157:H7 in Ruminants

Findings: Cattle can carry E. coli O157:H7 in their gastrointestinal tracts. Cattle also carry bacterial viruses (phage) that specifically kill E. coli O157:H7. It has been suggested that we use these phage to kill unwanted E. coli O157:H7 before cattle are slaughtered. We isolated 30 phage that killed E. coli O157:H7 from commercial feedlot cattle feces. We used these phage to reduce E. coli O157:H7 populations in sheep. We reduced E. coli O157:H7 populations approximately 100-fold in the gastrointestinal tract. We also found that adding more phage is not necessarily better, a lower dose of phage was more effective in killing E. coli O157:H7 than a 100-fold higher dose. We found that phage treatment was most effective against E. coli O157:H7 in the 24 hours immediately following treatment. These results indicate that phage could be used as a method to reduce E. coli O157:H7 in cattle before slaughter, but unfortunately, phage treatment is not the �ultimate� solution that we in the beef industry have sought. However, utilization of phage as one treatment in a multiple intervention or hurdle scheme could be effective; especially given the prevailing trend to reducing the use of antibiotics in cattle.