Bacterial translocation is bacterial species dependent: results using the human Caco-2 intestinal cell line

Because of in vivo limitations, the mechanisms underlying the process of bacterial translocation are poorly understood. Thus, an in vitro model system to study the translocation process was developed.

Transformed human colonic carcinoma (Caco-2) intestinal cells were grown as a polarized monolayer on semi-permeable membranes contained in the upper compartment of a two-compartment system. Once the Caco-2 monolayer had reached confluence, the ability of six different species of bacteria to translocate across the monolayer was tested using a dose-response curve of bacteria (10(2), 10(4), or 10(6)) organisms.

At inocula of 10(4) or 10(6) but not 10(2) organisms, bacteria crossed the monolayer. Bacterial passage across the monolayer was bacterial species specific, with gram-negative enterics being the best, gram-positive aerobes being intermediate translocators, and strict anaerobes being the poorest translocators.

The results of this study indicate that bacteria translocate across the Caco-2 monolayer in a dose-dependent and species-related fashion and support the use of this in vitro epithelial cell culture system as a model for studying bacterial transport.