FIGURE 1.

Host range and activity of BX001 bacteriophages. (a) Host range of each of the three selected phages in BX001 on a panel of 12 commercially and internally sourced C. acnes strains. Testing was carried out in triplicate by double layer agar spotting assay (see Appendix S1 in the Supporting Information). Dark green indicates total clearing of the spot or a number of plaques too numerous to count, light green indicates more than 10 plaques, yellow indicates between 1 and 10 plaques and red indicates that no plaques (no infectivity) were observed. (b) Sustained inhibition of C. acnes growth by BX001 cocktail (blue curve) as measured by OD (OD600) in a liquid culture at 37°C, compared to untreated bacterial growth (orange curve). OD600 measurements were carried out every 15 min in a Tecan Infinite M200 plate reader connected to a Tecan EVO75 robot. No spike in bacterial OD that would indicate the emergence of phage resistant bacteria was observed in the presence of BX001 phages over a period of 140 h. These results strongly suggest that the possibility of the emergence of a viable phage resistant bacterial strain upon administration of the BX001 cocktail has been greatly mitigated by design of a cocktail with phages originating from different environmental samples, and thus unlikely to occur together in nature, and possessing complementary characteristics indicating that they may be acting through different receptors