Fig. 1: Brucella abortus infects macrophages in the omentum and persists during the chronic phase.

a C57BL/6 mice were injected intraperitoneally (i.p.) with 1 × 10⁶ B. abortus strain 2308 CFU. At the indicated time points after infection of C57BL/6 mice, omentum (magenta), spleen (dark cyan), and peritoneal fluid (olive green) were analyzed for bacterial loads (mean of CFU per g, or for the peritoneal lavage per mL, from pooled data ± SD). 5 mice per group (but omentum day 8, 5-6 mice per group), n = 2. Significant differences from the spleen are displayed for the kinetics (two-way ANOVA followed by Dunnett’s multiple comparison test; F = 13.56; DF = 82) and between time points for organ individual points (Kruskal-Wallis followed by Dunn’s multiple comparison test). Absence of p-value, non-significant. b C57BL/6 mice were infected by gavage with 1 × 10⁹ B. abortus strain 2308 CFU. At 30 days post-infection (p.i.), omentum (magenta), spleen (dark cyan), and cervical lymph nodes (dark blue) were harvested, and CFU per g was determined. Each square represents one animal. Mean ± SD from pooled data. 4 mice per group, n = 2. Significant differences are shown (Kruskal-Wallis followed by Dunn’s multiple comparison test). Absence of p-value, non-significant. c Confocal microscopy image of wholemount staining of the omentum at day 8 p.i. from C57BL/6 mice i.p. infected with a DsRed strain of B. abortus. DsRed (Ba), F4/80 (green, macrophages), Ly6G (magenta, neutrophils), Ly6C (violet, monocytes, and blood vessels), B220 (pink, B cells) and CD3 (cyan, T cells). Individual stainings of cells present in the selected square are on the right. 3 mice, n = 4. Scale bar, 20 µm. d 3D reconstitution of cells in the square selected in (c), showing macrophage colonization by, and multiplication of, B. abortus. Top image, all labelings. Other images, Ba and F4/80 staining only. One square of the grid, 5 µm. Source data are provided as a Source Data file.