The effects of S-carboxymethylcysteine and N-acetylcysteine on the adherence of Moraxella catarrhalis to human pharyngeal epithelial cells

We investigated the effects of two mucoregulating drugs, S-carboxymethylcys teine (S-CMC) and N-acetylcysteine (NAC), on the attachment of Moraxella ca tarrhalis (M. catarrhalis) to pharyngeal epithelial cells. The attachment o f M, catarrhalis decreased (33-57%) significantly (P < 0.01) in a dose-depe ndent manner in cells treated with mucoregulating drugs as compared to the control. There was a significant (P < 0.01) decrease (35-45%) in the attach ment of M. catarrhalis to pharyngeal cells after oral administration of S-C MC, By electron microscopic observation, it was found that there was a fine , granular, electron-dense, ruthenium red-positive layer on the surface of pharyngeal epithelial cells; this layer was absent on cell surfaces treated with mucoregulating drugs. Possibly, this layer contained the portion of M . catarrhalis receptor which is responsible for the attachment of this bact eria to pharyngeal epithelial cells. From the above results, it may be conc luded that one of the mechanisms of mucoregulating drugs to decrease the ep isode of respiratory infections in patients with chronic respiratory diseas es is by inhibiting the attachment of bacteria to the upper respiratory tra ct.