Masson’s trichrome and PSR staining of caecal tissue from (a) CD1, (b) DBA/2 and (c) C57BL/6 mice following AIEC infection and from uninfected controls. Black arrows in the Masson’s trichrome panels indicate collagen deposition (green) in the submucosa and the mucosa surrounding inflammatory cellular infiltrates. White arrows in the PSR panels indicate collagen fibrils (large collagen fibers, yellow/orange; thinner fibers, green) in the muscularis mucosa, submucosa and mucosa. MM, muscularis mucosa; SM, submucosa; M, mucosa. Images are representative of two experiments with four mice per time point. Original magnification: × 200; scale bar, 200 μm.