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Endemic bacteriophages: A cautionary tale for evaluation of bacteriophage therapy and other interventions for infection control in animals

Kropinski, A.M., Lingohr, E.J., Moyles, D.M., Ojha, S., Mazzocco, A., She, Y.M., Bach, S.J., Rozema, E.A., Stanford, K., McAllister, T.A., Johnson, R.P. (2012). Endemic bacteriophages: A cautionary tale for evaluation of bacteriophage therapy and other interventions for infection control in animals, 9 http://dx.doi.org/10.1186/1743-422X-9-207

Abstract

Background: One of the most effective targets for control of zoonotic foodborne pathogens in the farm to fork continuum is their elimination in food animals destined for market. Phage therapy for Escherichia coli O157:H7 in ruminants, the main animal reservoir of this pathogen, is a popular research topic. Since phages active against this pathogen may be endemic in host animals and their environment, they may emerge during trials of phage therapy or other interventions, rendering interpretation of trials problematic. Methods. During separate phage therapy trials, sheep and cattle inoculated with 109 to 1010CFU of E. coli O157:H7 soon began shedding phages dissimilar in plaque morphology to the administered therapeutic phages. None of the former was previously identified in the animals or in their environment. The dissimilar rogue phage was isolated and characterized by host range, ultrastructure, and genomic and proteomic analyses. Results: The rogue phage (Phage vB-EcoS-Rogue1) is distinctly different from the administered therapeutic Myoviridae phages, being a member of the Siphoviridae (head: 53 nm; striated tail: 152 x 8 nm). It has a 45.8 kb genome which is most closely related to coliphage JK06, a member of the T1-like viruses isolated in Israel. Detailed bioinformatic analysis reveals that the tail of these phages is related to the tail genes of coliphage lambda. The presence of rogue phages resulting from natural enrichments can pose problems in the interpretation of phage therapeutic studies. Similarly, evaluation of any interventions for foodborne or other bacterial pathogens in animals may be compromised unless tests for such phages are included to identify their presence and potential impact. © 2012 Kropinski et al.; licensee BioMed Central Ltd.

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