Modulating effects of mucoregulating drugs on the attachment of Haemophilus influenzae

Non-typable Haemophilus influenzae (NTHI) is one of the three major pathoge ns implicated in human respiratory infections. The ability to attach with p haryngeal epithelial cells is an important factor for infection and virulen ce. In the present study we describe the effects of two mucoregulating drug s, S-carboxymethylcysteine (S-CMC) and ambroxol, on the attachment of NTHI to pharyngeal epithelial cells. There was a significant (P<0.0001, <0.001 a nd <0.01) decrease of attachment (8.8 +/- 2.4, 9.2 +/- 2.5 and 15.4 +/- 5.7 bacteria/cell) compared with the control (17.5 +/- 2.9, 15.5 +/- 3.1 and 1 8.8 +/- 6.8 bacteria/cell) after cells were treated wth S-CMC at a dose of 100, 10 and 1 <mu>g/ml. After attachment assay, cells treated with S-CMC (1 00 mug/ml) showed a significant decrease (P<0.01) of attached bacteria (3.1 +/- 0.8 bacteria/cell) compared with the control (5.9 +/- 1.8 bacteria/cel l). Treatment of cells with ambroxol did not influence bacterial attachment . By scanning electron microscopic observation it was found that NTHI attac hes to the surface elevations (microplicae) of human pharyngeal epithelial cells. Atomic force microscopic observation revealed that the surface poten tial of microplicae decreased significantly in cells treated with S-CMC com pared with the untreated control cells. As bacteria with negative surface c harge attach to the positively charged domain, i.e. microplicae of human ph aryngeal epithelial cells, this study suggests that the decrease of attachm ent of NTHI with epithelial cells after treatment with S-CMC was possibly d ue to the decrease of surface charge. This study suggests that S-CMC decrea ses the episodes of respiratory infections in patients with respiratory dis eases both by inhibiting the attachment of bacteria to the upper respirator y tract, and by detaching the adherent one. (C) 2001 Academic Press.