Figure 5

Macrophages are a key factor in the dissemination of MAC 101 and Mma20 bacteria to posterior body region. (A) Schematic of the experimental workflow. Zebrafish larvae were treated with 5 mM metronidazole (MTZ) at 1 dpf. After screening for the successful macrophage-ablated larvae, they were immersed with mCherry-labeled MAC 101 or DsRed-labeled Mma20 at 2.5 dpf for 2.5 dpi. (B,C) Representative fluorescence images showing bacterial dissemination in tlr2 wild-type and macrophage-ablated larvae after infection with MAC 101 (B) and Mma20 (C). Bacteria are shown in magenta. Scale bar: 100 µm. (D,E) Quantification of the bacterial burden in the anterior region (D) and the posterior region (E) after infection with MAC 101. (F,G) Quantification of the bacterial burden in the anterior region (F) and the posterior region (G) after infection with Mma20. Macrophage-ablated larvae exhibited significantly fewer bacteria in the posterior part of the body compared to non-ablated control larvae. For MAC 101 infection, the data from the tlr2^+/+ wild-type (n=21) group and macrophage-ablated group (n=21) are based on two independent experiments. For Mma20 infection, the data from the tlr2^+/+ wild-type (n=22) group and macrophage-ablated group (n=23) are also based on two independent experiments. Statistical significant difference was determined by one-way ANOVA, red arrows point to the median, ns, non-significant, *, P < 0.05, ****, P < 0.0001.