Adhesion of Enterococcus mundtii ST4SA and Lactobacillus plantarum 423 to Caco-2 (human carcinoma epithelial) cells was visualized by fluorescent staining. Both strains showed good adhesion compared to L. casei MB1, L. casei Shirota, L. johnsonii La1 and L. rhamnosus GG. No correlation was found between hydrophobicity, aggregation and adhesion to Caco-2 cells. Presence of antibiotics and anti-inflammatory medicaments reduced adhesion of bacterial strains to Caco-2 cells. Proteins sensitive to pepsin, trypsin and pronase are involved in the adhesion of E. mundtii ST4SA and L. plantarum 423 to Caco-2 cells. Adhesion of Listeria monocytogenes ScottA to Caco-2 cells was not prevented by E. mundtii ST4SA and L. plantarum 423. Cell-free culture supernatants of strains ST4SA and 423, containing the antimicrobial peptides plantaricin 423 and peptide ST4SA, prevented the invasion of L. monocytogenes ScottA into Caco-2 cells.