The Bps polysaccharide of Bordetella pertussis promotes colonization and biofilm formation in the nose by functioning as an adhesin.

Many respiratory pathogens establish persistent infection or a carrier state in the human nasopharynx without overt disease symptoms but the presence of these in the lungs usually results in disease. Although the anatomy and microenvironments between nasopharynx and lungs are different, a virulence factor with an organ-specific function in the colonization of the nasopharynx is unknown. In contrast to the severity of pertussis and mortality in non-vaccinated young children, Bordetella pertussis results in milder and prolonged cough in vaccinated adolescents and adults. Individuals harbouring bacteria in the nasopharynx serve as reservoirs for intrafamilial and nosocomial transmission. We show that the Bps polysaccharide of B. pertussis is critical for initial colonization of the mouse nose and the trachea but not of the lungs. Our data reveal a biofilm lifestyle for B. pertussis in the nose and the requirement of Bps in this developmental process. Bps functions as an adhesin by promoting adherence of B. pertussis and Escherichia coli to human nasal but not to human lung epithelia. Patient serum specifically recognized Bps suggesting its expression during natural human infections. We describe the first bacterial factor that exhibits a differential role in colonization and adherence between the nasopharynx and the lungs.