Figure 2. Phage Therapy Did Not Select for Phage-resistant Isolates.

(A) Efficiencies of plating of phages on M. smegmatis mc²155 and six M. abscessus isolates from the subject -1437, -323 and -60 days prior to initiation of phage therapy, as well as 5, 44, and 245 days after therapy started. Phage lysates were 10-fold serially diluted and spotted onto top agar overlays of each strain. Phages BPΔ33HTH_HRM^GD03, BPΔ33HTH_HRM10, Muddy, Itos, D29 and D29_HRM^GD40 infect each M. abscessus isolate with similar efficiencies to M. smegmatis mc²155. Phage BPΔ33HTH_HRM10, which was used therapeutically previously (Dedrick et al., 2021b; Dedrick et al., 2019), and D29_HRM^GD40 were chosen as therapeutic candidates; phage Itos infects efficiently but does not kill the M. abscessus strains tested well.

(B) Killing of M. abscessus strain collected -1437 days prior to initiation of phage by BPΔ33HTH_HRM10, D29_HRM^GD40 or both phages. Each column has a 10-fold serial dilution of the isolate (left column, 2×10⁵ CFU) and each row has 10-fold serial dilutions of either BPΔ33HTH_HRM10 (top row, 10⁹ PFU), D29_HRM^GD40 (top row, 10⁷ PFU) or both phages.

(C) Survival assay showing efficient killing of M. abscessus strain collected -1437 days prior to initiation of phage with either BPΔ33HTH_HRM10 or D29_HRM^GD40 or both phages together.

(D) Phage susceptibility assays of two survivors recovered from a challenge with BPΔ33HTH_HRM10 and D29_HRM^GD40 of M. abscessus strain collected -1437 days prior to initiation of phage shows both are fully phage-sensitive. Phages were tested as in panel A.