Oral and rectal administration of bacteriophages for control of Escherichia coli O157:H7 in feedlot cattle.
This study compared oral and rectal administration of O157-specific bacteriophages for mitigating the fecal shedding of Escherichia coli O157 by experimentally inoculated steers. Fecal shedding of nalidixic acid-resistant (Nal(R)) E. coli O157:H7 was monitored over 83 days after oral (ORL; 3.3 x 10(11) PFU), rectal (REC; 1.5 x 10(11) PFU), both oral and rectal (O+R; 4.8 x 10(11) PFU), or no (CON; control) treatment with a four-strain O157-specific bacteriophage cocktail in multiple doses. Bacteriophages were enumerated by plaque assay, and NalR E. coli O157:H7 by direct plating on sorbitol MacConkey agar supplemented with cefixime, potassium tellurite, and nalidixic acid. Orally treated steers produced the fewest Nal(R) E. coli O157:H7 culture-positive samples (P < 0.06) compared with REC and O+R steers, but this number was only nominally lower (P = 0.26) than that for the CON steers. The overall mean shedding level (log CFU per gram of feces) was higher for REC steers (P < 0.10) than for steers of the other treatment groups. Despite the shedding of higher mean bacteriophage levels (log PFU per gram of feces) by ORL and O+R than by CON and REC steers, there was no difference (P > 0.05) in the number of E. coli O157-positive samples among treatments. Bacteriophage was isolated from CON steers, indicating that these steers acquired the bacteriophage from the environment and shed the phage at a level similar to that of REC steers (P = 0.39). Continuous bacteriophage therapy may be an efficacious method for mitigating shedding of E. coli O157:H7 in cattle, providing that the host bacterium does not develop resistance. This therapy may be especially advantageous if nontreated cattle can acquire this biocontrol agent from the feedlot environment.
Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta, Canada T6G 2P5.
Erica A
EA
Rozema
Tyler P
TP
Stephens
Susan J
SJ
Bach
Erasmus K
EK
Okine
Roger P
RP
Johnson
Kim
K
Stanford
Tim A
TA
McAllister
D000284:Administration, Oral; D000285:Administration, Rectal; D000818:Animals; D001435:Bacteriophages / Q000502:physiology*; D002417:Cattle; D002418:Cattle Diseases / Q000382:microbiology / Q000635:transmission*; D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D004927:Escherichia coli Infections / Q000382:microbiology / Q000635:transmission / Q000662:veterinary*; D019453:Escherichia coli O157 / Q000254:growth & development / Q000302:isolation & purification*; D005243:Feces / Q000382:microbiology*; D005506:Food Contamination / Q000517:prevention & control*; D005516:Food Microbiology; D008297:Male; D011897:Random Allocation