The Efficacy of Selected Probiotic Strains and Their Combination to Inhibit the Interaction of Adherent-Invasive Escherichia coli (AIEC) with a Co-Culture of Caco-2:HT29-MTX Cells

Abstract

The gastrointestinal tract's microbiota plays a crucial role in human health, with dysbiosis linked to the development of diseases such as inflammatory bowel disease (IBD). Whilst the pathogenic mechanisms underlying IBD remain poorly characterised, adherent-invasive Escherichia coli (AIEC) has been implicated as a microbiological factor in disease pathogenesis. These strains show an enhanced ability to diffusely adhere to and invade intestinal epithelial cells, along with the ability to survive and replicate within macrophages. Probiotics, such as Lactobacillus strains, have been identified as potential treatment options due to their abilities to compete with pathogens for binding sites and regulate the host immune response. In this study, we used four well-characterised Lactobacillus strains and their combination to test their ability to inhibit the adhesion, invasion, and translocation of a well-characterized AIEC strain, F44A-1, in a co-culture of Caco-2 and HT29-MTX cell lines representing the gut epithelium. The results demonstrated that the pre-inoculation of the probiotic candidates 90 min prior to the introduction of the AIEC was more effective in inhibiting AIEC interaction than the co-inoculation of the strains. While the individual probiotic strains greatly reduced AIEC colonisation and invasion of the co-cultured cells, their combination was only more effective in reducing the translocation of the AIEC. These results suggest that probiotics are more effective when used prophylactically against pathogens and that the combination of strains may enhance their efficacy against AIEC translocation once used as a prophylactic measure.

Keywords: AIEC; Caco-2:HT29-MTX cells; pre- and co-inoculation; probiotic combination.

Figure 1

(a) The percentage (mean ± SEM) colonization of the co-culture of Caco-2:HT29-MTX cells by the AIEC alone and in the presence of the Lactobacillus strains when co-inoculated and pre-inoculated . (b) The number (mean ± SEM) of adhering AIEC alone and in the presence of the Lactobacillus strains when co-inoculated and pre-inoculated . E. coli strain 46.4 used as negative control . * p < 0.0001 co-inoculation versus pre-inoculation ** p < 0.0001 combination versus individual strain.

Figure 2

The number (mean ± SEM) of invading AIEC (CFU) alone and in the presence of Lactobacillus strains when co-inoculated and pre-inoculated . E. coli strain 46.4 used as negative control . * p < 0.0001 co-inoculation versus pre-inoculation.

Figure 3

The number (mean ± SEM) of translocating AIEC (CFU) alone , when in the presence of Lactobacillus strains M4-205 , M4-100 , M4-195 , M4-165 , and their combination . E. coli strain HMLN1 was used a positive control and E. coli strain JM109 as a negative control . (a) Co-inoculation of AIEC and probiotic candidates after 30 min interaction; (b) co-inoculation of AIEC and probiotic candidates after 120 min interaction; (c) pre-inoculation of AIEC and probiotic candidates after 30 min interaction; (d) pre-inoculation of AIEC and probiotic candidates after 120 min interaction.