Salmonella Typhimurium discreet-invasion of the murine gut absorptive epithelium
Fig 2
Infections in inflammasome-deficient mice confirm the dependence on SipA for S.Tm absorptive epithelial cell invasion in vivo.
(A-E) Deletion of SipA has a profound impact on absorptive epithelial cell invasion in the mouse gut. Inflammasome-deficient (Nlrc4-/-) mice were orally infected with the indicated S.Tm/pssaG-GFP reporter strains for 18h. (A) S.Tm CFU counts in cecum content. (B) Representative micrographs of the cecal mucosa upon infection with the indicated strains. Lu.—Lumen; Ep.—Epithelium; L.p.—Lamina propria. White arrow heads indicate intraepithelial S.Tm. Scale bar: 10μm. (C) Microscopy-based quantification of intraepithelial S.Tm per 20μm section. (D) S.Tm CFU counts in cecal mucosa tissue. In A, C, and D each data point corresponds to one animal. Line at median. (C-D) Mann-Whitney U-test (**p<0.01). (E) Representative micrographs of the extensively washed cecal mucosa. Blow-up in rightmost panel highlights S.TmΔsipA on the epithelial surface (white arrow heads). Lu.—Lumen; Ep.—Epithelium. Scale bar: 50μm. (F) Barcoded consortium infections reveal the differential dependence on bacterial virulence factors for S.Tm invasion of epithelial cell lines vs. the gut absorptive epithelium in mice. Relative abundance of the indicated barcoded S.Tm strains in the intracellular population in HeLa cells (left panel; 20min infection at MOI 0.2–2) and in vivo in the cecal mucosa of Nlrc4-/- mice (right panel; infected as in A above). Bars correspond to mean +/- SD of six replicate infections pooled from two different occasions (left panel) or infection of seven replicate mice (right panel). Each replicate is indicated by a circle symbols. One-way ANOVA with Dunnett´s test (n.s., not significant; *p<0.05, ***p<0.001).