Isolation and Characterization of a New T-Even Bacteriophage, CEV1, and Determination of Its Potential To Reduce Escherichia coli O157:H7 Levels in Sheep

Abstract

Bacteriophage CEV1 was isolated from sheep resistant to Escherichia coli O157:H7 colonization. In vitro, CEV1 efficiently infected E. coli O157:H7 grown both aerobically and anaerobically. In vivo, sheep receiving a single oral dose of CEV1 showed a 2-log-unit reduction in intestinal E. coli O157:H7 levels within 2 days compared to levels in the controls.

Naturally resident and exogenously applied T4-like and T5-like bacteriophages can reduceEscherichia coliO157

“…26,[33][34][35] A number of authors have demonstrated the efficacy of either single or cocktail phage treatments in the laboratory but only a few have shown any meaningful reduction in vivo. [23][24][25]27,28,36,37 Early studies examining phage populations in livestock were born of a concern that they might negatively affect the microbial ecology of the gut (especially the rumen) and thus reduce animal productivity; however, it was found that phage actually help maintain microbial diversity and balance. 38,39 These initial studies centered on bovine ruminal phages, but more recent O157:H7 phage research has moved to the recto-anal junction, the demonstrated major site of colonization in cattle.…”

“…We have previously described a T4-like myovirus, CEV1, isolated at the USDA/ARS (College Station, Texas) from a flock of sheep resistant to gut colonization by E. coli O157:H7 (EDL 933 and NCTC 12900), its subsequent characterization and evaluation as a treatment to remove resident O157:H7 from sheep. 25 Before beginning the in vivo trial, fresh directly-sampled fecal material from the target sheep was screened for O157:H7-infecting phages. None were found on direct sampling, but 20 of the 39 and their chief associated foodborne pathogens (Campylobacter, Salmonella and E. coli O157:H7).…”

“…25 In this paper we describe our characterization of this new phage and its use in conjunction with CEV1 against O157:H7 in sheep. All 20 of the new isolates had similar plaque morphology and were found to have the same host range when tested against the 18 strains of the FDIU O157:H7 collection after plaque purification.…”

“…22 The use of such phages to target a variety of gastrointestinal pathogens is one potential control strategy being examined by a number of researchers, but in vivo attempts targeting E. coli O157:H7 have yielded mixed results to date. [23][24][25][26][27][28] Although phages have long been known to play a key role in the gastrointestinal ecosystem, very few systematic studies of their prevalence, distribution, variety and importance in cattle or other food animals have been undertaken. This lack of basic knowledge is being addressed as researchers have begun to consider the use of bacteriophages in both pre-and post-harvest pathogen reduction strategies.…”

Development of a risk-based index for source water protection planning, which supports the reduction of pathogens from agricultural activity entering water resources

“…Animals carrying zoonoses, such as E. coli O157:H7 may be symptom-free, so producers may be unaware that a problem exists. Pathogen concentrations in faeces may be reduced by employing probiotics (Fuller, 1999), vaccine technology (Glass, 2004) or the use of bacteriophages specific to an individual species or strain (Raya et al, 2006).…”