MUC5AC and cystic fibrosis: Mucus is a protecting layer that entraps and clears foreign materials, including bacteria, out of the lungs.15, 16 Unfortunately, mucus clearance is often compromised in disease states such as CF, which might promote the development of bacterial resistance.17 Hence, we investigated the pyocyanin production of PA14 wt in the presence of mucin, the main organic component of mucus, and in the presence of crude, native human tracheal mucus.