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Fig. 1 Virulence of the M. abscessus ESX-3 mutant in zebrafish larvae. (A) Genetic organization of the esx-3 locus in Mab WT and ΔeccC3. (B) Schematic overview of the in vivo experiments. (C) Survival of infected larvae up to 12 days post-infection (dpi). The graph shows results from three pooled independent experiments with at least n=24 larvae per strain per experiment. Larvae were considered dead in the absence of a heartbeat. Statistical analysis was performed using the Log-rank (Mantel-Cox) test. (D) Bacterial burden of infected larvae at 3 dpi and 5 dpi. The graph shows results from three pooled independent experiments with n=5 larvae per strain per timepoint per experiment. CFU counts were Log10 transformed. Statistical analysis was performed using ordinary one-way ANOVA with Tukey’s multiple comparisons test, after verifying the normality of the data. (E) Representative images of infected larvae with R, R ΔeccC3, and R ΔeccC3::c at 3 dpi (left panels) and 5 dpi (right panels). Images were acquired in Widefield mode (Axiocam 712) with a TL LED lamp for Brightfield and an LED-Module 590 nm for mScarlet and tdTomato. Scale bar=500 µm.