Inhibitory effect of N-acetylcysteine on adherence of Streptococcus pneumoniae and Haemophilus influenzae to human oropharyngeal epithelial cells in vitro

Background: Bacterial adherence to mucosal and epithelial cell structures i s of importance for the persistence of bacteria in the airways. Cigarette s moking and chronic bronchitis are associated with increased bacterial adher ence. N-Acetylcysteine (NAC) medication reduces the number of infectious ex acerbations in patients with chronic bronchitis, and NAC medication has bee n associated with low intrabronchial bacterial numbers. Objective: We inves tigated whether NAC influences bacterial adherence as a possible mechanism behind its clinical effects. Methods: Highly adhering test strains of Strep tococcus pneumoniae and Haemophilus influenzae were used to investigate the influence of four pharmacological compounds on adherence to oropharyngeal epithelial cells in vitro. Adhesion assays were performed both during short -term exposure to, as well as after long-time incubation with, NAG, lidocai ne, hydrocortisone and terbutaline at concentrations not inhibiting bacteri al growth. Results: Only NAC showed a significant inhibitory effect on adhe sion of H. influenzae during short-term incubation. After long-term incubat ion, both NAC and hydrocortisone inhibited bacterial adhesion for both stra ins in a dose-dependent manner. When NAC's effect on three different strain s of S. pneumoniae and four strains of H. influenzae was studied, inhibitio n of bacterial adhesion was found for th ree strains of each species. Concl usions: NAC lowers bacterial adhesion in vitro to oropharyngeal epithelial cells in doses equivalent to that is being used clinically. This effect mig ht be a contributory mechanism behind the reduction of infectious exacerbat ions in chronic bronchitis patients. Copyright (C) 2000 S. Karger AG, Basel .