Naturally resident and exogenously applied T4-like and T5-like bacteriophages can reduce Escherichia coli O157:H7 levels in sheep guts

摘要: In preparing sheep for an in vivo Escherichia coli O157:H7 eradication trial, we found that 20/39 members of a single flock were naturally colonized by O157:H7-infecting phages. Characterization showed these all one phage type (subsequently named CEV2) infecting 15/16 O157:H7, 7/72 ECOR and common lab strains. Further characterization PFGE (genome∼120 kb), restriction enzyme digest (DNA appears unmodified), receptor studies (FhuA but not TonB is required infection) sequencing (>95% nucleotide identity) it close relative the classically studied coliphage T5. Unlike T5, CEV2 infects vitro, both aerobically anaerobically, rapidly adsorbing killing, resistant mutants regrew within 24 h. When used together with T4-like CEV1 (MOI ∼2 per phage), bacterial killing was longer lasting. did reproduce when co-infecting same cell as CEV1, presumably succumbing to CEV1's ability shut off transcription cytosine-containing DNA. trials remove resident cocktail (∼10(11) total PFU) applied once orally more effective (>99.9% reduction) than alone (∼99%) compared untreated phage-free control. Those carrying CEV2, receiving no additional treatment, had lowest levels (∼99.99% reduction). These data suggest cocktails are individual removing have taken residence if work concert another phages may prevent gut colonization be explanation transient ruminants.