Bacterial adhesiveness: effects of the SH metabolite of erdosteine (mucoactive drug) plus clarithromycin versus clarithromycin alone.

After metabolization, erdosteine (a mucoactive drug) produces an active metabolite (Met I) with an SH group that is capable of opening disulphide bonds, including those of pilin, a protein of bacterial fimbriae. This induces stereochemical conformational changes that interfere with the binding of bacterial adhesins (fimbriae) to receptors on eukaryotic cells. At subinhibitory concentrations, the macrolide clarithromycin inhibits the expression of adhesins on bacterial cell surfaces. The addition of 5 and 10 microg/ml of Met I to 1/8, 1/16 and 1/32 MIC of clarithromycin potentiated the inhibition of Staphylococcus aureus adhesiveness to human mucosal cells in comparison with the antibiotic alone. This finding opens up a new possibility of interfering with bacterial adhesiveness and its resulting pathogenicity not only by using antibiotics but also by means of their combination with agents devoid of antibacterial activity.