CF patients may also have their airways chronically colonized by filamentous fungi (such as "Aspergillus fumigatus", "Scedosporium apiospermum", "Aspergillus terreus") and/or yeasts (such as "Candida albicans"); other filamentous fungi less commonly isolated include "Aspergillus flavus" and "Aspergillus nidulans" (occur transiently in CF respiratory secretions) and "Exophiala dermatitidis" and "Scedosporium prolificans" (chronic airway-colonizers); some filamentous fungi such as "Penicillium emersonii" and "Acrophialophora fusispora" are encountered in patients almost exclusively in the context of CF. Defective mucociliary clearance characterizing CF is associated with local immunological disorders. In addition, the prolonged therapy with antibiotics and the use of corticosteroid treatments may also facilitate fungal growth. Although the clinical relevance of the fungal airway colonization is still a matter of debate, filamentous fungi may contribute to the local inflammatory response and therefore to the progressive deterioration of the lung function, as often happens with allergic bronchopulmonary aspergillosis – the most common fungal disease in the context of CF, involving a Th2-driven immune response to "Aspergillus" species.