INTRODUCTION: The capsular polysaccharide (CPS) of pathogenic bacteria is a critical virulence factor, often evading phagocytosis by host immune cells, while also interfering with the contact of the pathogen with host cells and contributing to biofilm formation. METHODS: In this study, we generated a non-encapsulated mutant ( RESULTS: Infection of A549 lung epithelial cells showed similar adherence levels for the wild-type and non-capsulated strain, while our data showed a moderately higher internalization of DISCUSSION: In conclusion, our data indicate a crucial role of CPS