Confocal laser sections of Caco-2 monolayers treated with C . jejuni 81-176 plus non-invasive GFP Escherichia coli C25 (arrows) and stained with the absorptive enterocyte marker Ulex europaeus agglutinin-1 (red). E. coli are color-coded according to their respective depth within the monolayer from extracellular (yellow) to intracellular (blue). (a) Merge of all confocal laser sections. (b-e) Representative confocal laser sections starting from the apical surface of the monolayer (E. coli color-coded yellow) to the basolateral surface of the monolayer (E. coli color-coded blue).