Application of bacteriophages to control intestinal Escherichia coli O157:H7 levels in ruminants.
A previously characterized O157-specific lytic bacteriophage KH1 and a newly isolated phage designated SH1 were tested, alone or in combination, for reducing intestinal Escherichia coli O157:H7 in animals. Oral treatment with phage KH1 did not reduce the intestinal E. coli O157:H7 in sheep. Phage SH1 formed clear and relatively larger plaques on lawns of all 12 E. coli O157:H7 isolates tested and had a broader host range than phage KH1, lysing O55:H6 and 18 of 120 non-O157 E. coli isolates tested. In vitro, mucin or bovine mucus did not inhibit bacterial lysis by phage SH1 or KH1. A phage treatment protocol was optimized using a mouse model of E. coli O157:H7 intestinal carriage. Oral treatment with SH1 or a mixture of SH1 and KH1 at phage/bacterium ratios > or = 10(2) terminated the presence of fecal E. coli O157:H7 within 2 to 6 days after phage treatment. Untreated control mice remained culture positive for >10 days. To optimize bacterial carriage and phage delivery in cattle, E. coli O157:H7 was applied rectally to Holstein steers 7 days before the administration of 10(10) PFU SH1 and KH1. Phages were applied directly to the rectoanal junction mucosa at phage/bacterium ratios calculated to be > or = 10(2). In addition, phages were maintained at 10(6) PFU/ml in the drinking water of the phage treatment group. This phage therapy reduced the average number of E. coli O157:H7 CFU among phage-treated steers compared to control steers (P < 0.05); however, it did not eliminate the bacteria from the majority of steers.
Sheng
Haiqing
H
University of Idaho, Department of Microbiology, Molecular Biology, and Biochemistry, Moscow, ID 83844-3052, USA.
Knecht
Hannah J
HJ
Kudva
Indira T
IT
Hovde
Carolyn J
CJ
D000818:Animals; D001433:Bacteriolysis; D002417:Cattle; D002418:Cattle Diseases / Q000382:microbiology / Q000628:therapy; D003090:Coliphages / Q000502:physiology*; D004326:Drinking; D004927:Escherichia coli Infections / Q000382:microbiology / Q000628:therapy; D019453:Escherichia coli O157 / Q000472:pathogenicity / Q000502:physiology* / Q000821:virology*; D005618:Fresh Water / Q000821:virology; D007422:Intestines / Q000382:microbiology / Q000821:virology; D008242:Lysogeny; D051379:Mice; D012418:Ruminants / Q000382:microbiology / Q000821:virology; D012756:Sheep; D012757:Sheep Diseases / Q000382:microbiology / Q000628:therapy; D010948:Viral Plaque Assay