Comparació de la capacitat d'adhesió i invasió d’Escherichia coli adherent invasiva (AIEC) en dues línies cel·lulars (I-407 i Caco-2)

Abstract

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