In 2004, Dr. Darfeuille-Michaud's group described a new pathotype of E. coli that they
named adherent-invasive Escherichia coli (AIEC), given that its characteristics could not be
related to any of the pathogenic traits of the E. coli causing gastrointestinal infections known
so far. Furthermore, it was proved to be more prevalent in patients with Crohn's disease.
Many studies have focused on studying the mechanisms of pathogenicity of pathotypes and
finding a molecular marker for their detection. Nowadays, identification is based on the
infection of cell cultures in vitro to determine the ability to adhere to and invade epithelial
intestinal cells and the survival and replication ability in macrophages. This implies that the
identification of AIEC is challenging and can hardly be standardised. Moreover, there is a
great diversity of protocols used, adding to the variability of the results.
This work consists of two parts. A bibliographical part in which the different protocols used
in studies involving the main cell models (Caco-2 and I-407) are reviewed. Additionally, of
these studies, the variability of the invasion rates of the LF82 and K12 strains into the two
cell models is analyzed in order to determine the variability between the cell types. An
experimental part was also carried out, in which the adhesion and invasion of AIEC and nonAIEC strains onto Caco-2 was determined and compared with the data obtained with the I407 model.
The results allowed us to observe the huge methodological variability that exists in the
literature, but we can mainly highlight one method for adhesion (MOI: 10 and t of infection:
3 h) and another for invasion (MOI: 10, t of infection: 3h, antibiotic concentration: 100
µg/ml and t with antibiotic: 1 h). When comparing the indices from the bibliography, it has
been observed that for the two strains, LF82 and K12, they are higher in the Caco-2 cells
than in the I-407 cells. For the invasion indexes, no significant differences were found in the
AIEC strains, so the two cell models would classify the strains the same way. For the
adhesion indices, they were found to be higher for the Caco-2 cells with a higher degree of
differentiation (15 days). For non-AIEC strains, the invasion rates obtained were very high
for Caco-2, a very surprising result that needs to be corroborated. In conclusion, despite the
differences observed among the indices, the two cell lines appear to be good models for
AIEC identification, but the protocols for Caco-2 need to be adjusted in order to obtain an
adequate identification, especially for non-AIEC strains
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