Bacteriophage therapy for controlling Escherichia coli O157:H7 in feedlot cattle

Oral and rectal administration of bacteriophage was compared for mitigating the fecal shedding of Escherichia coli O157:H7 by inoculated steers. Shedding of nalidixic acid-resistant (NalR) E. coli O157:H7 was monitored over 83 D following oral (3.3 x 10 11 pfu), rectal (1.5 x 1011 pfu), both oral and rectal (4.8 x 1011 pfu) or no treatment with an O157-specific bacteriophage cocktail. Orally treated steers presented the fewest (P = 0.06) NalR E. coli O157:H7 culture-positive samples compared to rectally and orally + rectally treated steers. This may be attributed to higher (P = 0.03) mean bacteriophage shedding levels (log PFU/g of feces) in orally treated than in rectally treated steers. Control animals obtained bacteriophage via the environment, and shed at levels similar to that of REC (P = 0.39). Oral administration of bacteriophage via the feedlot environment may be an efficacious large-scale mitigation strategy for E. coli O157:H7 in cattle.