Fig. 3: Virulence assays.

a Chronological evolution of the mean activity score of Gm larvae injected with phosphate-buffered saline (control) or any of the seven Pseudomonas aeruginosa isolates retrieved just before (Pa1_BS) and during (Pa2_BR−Pa7_BS) phage therapy. Full lines represent the mean activity scores of Gm larvae injected with any of four PNM-resistant P. aeruginosa isolates (Pa2_BR and Pa4_BR−Pa6_LR) or phosphate-buffered saline (PBS). Dashed lines were used for the three PNM-susceptible isolates (Pa1_BS, Pa3_LS, and Pa7_BS). Note that first shown measurement after injection starts at +5 h. Real scale standard deviations were not visually implementable, but the dot width of each final mean measurement correlates with its standard deviation. n = 10 biologically independent animals. b Log-rank test finds the three liver abscess-borne strains (Pa3_LS, Pa5_LR, and Pa6_LR) significantly more virulent than the bloodborne strains (Pa1_BS, Pa2_BR, Pa4_BR, and Pa7_BS): p value = 0.0011. c Conversely, Log-rank test shows no significant difference in virulence when comparing the three phage-susceptible strains (Pa1_BS, Pa3_LS, Pa7_BS) with the four phage-resistant strains (Pa2_BR, Pa4_BR, Pa5_LR, Pa6_LR): p value = 0.7552. d The absorbance at 570 nm was measured to evaluate the viability of HeLa cells. The highly virulent P. aeruginosa strain PA14 was used as a positive control whereas HeLa cells without the addition of a P. aeruginosa culture served as a negative control. A connected letter report was created to pairwise compare all isolates and controls (two-sided Student’s t test, p value = 0.05, n = 6 biologically independent samples, no adjustment made for multiple comparisons). Pa1_BS was found to not significantly reduce the viability of the cells, compared to the negative control. Box-plots elements: center line, median; box limits, upper and lower quartiles; whiskers, 1.5× interquartile range; points, individual values. Source data are provided as a Source Data file.