Aspergillus Biofilm In Vitro and In Vivo.

In vivo, Aspergillus fumigatus grows as a typical biofilm with hyphae covered by an extracellular matrix (ECM) composed of polysaccharides, galactomannan, and galactosaminogalactan. α1,3 glucans and melanin are also constitutive of the ECM in aspergilloma but not in invasive aspergillosis. In vitro, two biofilm models were established to mimic the in vivo situation. The first model (model 1) uses submerged liquid conditions and is characterized by slow growth, while the second model (model 2) uses agar medium and aerial conditions and is characterized by rapid growth. The composition of the ECM was studied only in the second model and has been shown to be composed of galactomannan, galactosaminogalactan (GAG), and α1,3 glucans, melanin, antigens, and hydrophobins. The presence of extracellular DNA was detected in model 1 biofilm but not in model 2. Transcriptomic analysis employing both biofilm models showed upregulation of genes coding for proteins involved in the biosynthesis of secondary metabolites, adhesion, and drug resistance. However, most data on A. fumigatus biofilms have been obtained in vitro and should be confirmed using in vivo animal models. There is a need for new therapeutic antibiofilm strategies that focus on the use of combination therapy, since biofilm formation poses an important clinical problem due to their resistance to antifungal agents. Furthermore, in vivo investigations of A. fumigatus biofilms that incorporate the associated microbiota are needed. Such studies will add another layer of complexity to our understanding of the role of A. fumigatus biofilm during lung invasion.