Bacterial communities are associated with intracellular neutrophils in urinary bladder transitional epithelial cells (A) and gall bladder mucosal epithelial cells (B). Female C57BL/6 mice were challenged by intra-urethral inoculation with 107 CFUs human urinary pathogenic E. coli strain UTI89 and its bladder was harvested 24 h after infection. Whole mounts of urinary bladder were stained with cytox orange (light green in A), DAPI (blue in A) and WGA (false colored dark green in A). Confocal laser microscopy demonstrates a large aggregation of intracellular bacterial community (IBC) in superficial umbrella bladder epithelial cell (yellow arrow in A) and intraepithelial neutrophil (white arrow in A; see also Additional file 2). Female C57BL/6 mice were challenged by injection of 105 CFUs of Salmonella enterica serovar Typhimurium/PoxyS-gfp strain SL1344 into the gall bladder which was harvested 24 h after infection. Whole mounts of gall bladder were stained with DAPI (blue in B) and phalloidin-TRITC (red in B). Confocal laser microscopy demonstrates GFP-expressing bacteria in gall bladder epithelial cells and intraepithelial neutrophils (white arrows in B; see also Additional file 3). The xy images are on the plan indicated by the horizontal and vertical dashed lines shown in the xz and yz images, respectively. Original magnification X63 (A, B). All images are representative of the entire sample. The histological morphology and pathology results were very similar for each organ in a given mouse and between mice.