Host range and lytic capability of four bacteriophages against bovine and clinical human isolates of Shiga toxin-producing Escherichia coli O157:H7.
OBJECTIVE
To evaluate host range and lytic capability of four bacteriophages (rV5, wV7, wV8 and wV11) against Escherichia coli O157:H7 (STEC O157:H7) from cattle and humans.


RESULTS
Four hundred and twenty-two STEC O157:H7 isolates (297 bovine; 125 human) were obtained in Alberta, Canada. The four phages were serially diluted and incubated for 5 h with overnight cultures of STEC O157:H7 to estimate their multiplicity of infection (MOI). All bovine STEC O157:H7 were subjected to pulsed-field gel electrophoresis (PFGE) and phage typing (PT). Phage wV7 lysed all human and bovine isolates irrespective of PFGE genotype or PT phenotype and exhibited the lowest MOI (0.004-0.006, P < 0.0001) of all phages. Phages rV5 and wV11 exhibited a lower MOI (0.002-0.04, P < 0.0001) than did phage wV8 (25-29) and they had a narrower host range than wV7 or wV8. Phages rV5, wV11 and wV8 lysed 342 (81.0%), 321 (76.1%) and 407 (96.4%), respectively, of the 422 isolates. Susceptibility of bovine STEC O157:H7 to rV5, w11 and wV8 was influenced by PFGE genotype and/or PT phenotype.


CONCLUSIONS
Phages exhibited activity against the majority of bovine and human STEC O157:H7 isolates. PFGE genotype and/or PT phenotype of the host-target influenced their vulnerability to phage attack. Susceptibility of bovine STEC O157:H7 to phage may also differ among farms. Both lytic capability and host range should be considered in the selection of therapeutic phage for on-farm control of STEC O157:H7.


CONCLUSIONS
The present work indicates that a four-phage cocktail should be equally effective at mitigating STEC O157:H7 isolates both of bovine and of human origin. Given that some STEC O157:H7 exhibited resistance to some but not all phages, a phage cocktail is the logical approach to efficacious on-farm therapy.
Niu
Y D
YD
Department of Bioscience and Biotechnology, Dalian University of Technology, Dalian, Liaoning, China.
Johnson
R P
RP
Xu
Y
Y
McAllister
T A
TA
Sharma
R
R
Louie
M
M
Stanford
K
K
D000818:Animals; D001431:Bacteriological Techniques; D001433:Bacteriolysis; D001434:Bacteriophage Typing; D001435:Bacteriophages / Q000235:genetics / Q000254:growth & development* / Q000302:isolation & purification; D002170:Canada; D002417:Cattle; D016521:Electrophoresis, Gel, Pulsed-Field; D019453:Escherichia coli O157 / Q000235:genetics* / Q000302:isolation & purification / Q000821:virology*; D005838:Genotype; D006801:Humans; D010641:Phenotype