Background : The genusPseudomonasincludes a heterogeneous set of microorganisms that can be isolated frommany different niches and nearly 100 different strains have been described. The best characterized bacterium is Pseudomonas aeruginosawhich is the primary agent of opportunistic infection in humans, causing both acute andchronic infections. Other species likefluorescens,putidaormosseliihave been sporadically isolated from hospitalizedpatients but their association with the pathology often remains unclear. Results : This study focuses on the cytotoxicity and inflammatory potential of two strains ofPseudomonas mosselii(ATCC BAA-99 and MFY161) that were recently isolated from clinical samples of hospitalized patients. The behaviorof these bacteria was compared to that of the well-known opportunistic pathogenP. aeruginosaPAO1. We foundthatP. mosseliiATCC BAA-99 and MFY161 are cytotoxic towards Caco-2/TC7 cells, have low invasive capacity,induce secretion of humanβ-defensin 2 (HBD-2), alter the epithelial permeability of differentiated cells and damagethe F-actin cytoskeleton. Conclusions : These data bring new insights intoP. mosseliivirulence, since this bacterium has often beenneglected due to its rare occurrence in hospital.