Our Current Understanding of Fungal Biofilms

Abstract

Fungal biofilms are an escalating clinical problem associated with significant rates of mortality. Candida albicans is the most notorious of all fungal biofilm formers. However, non-Candida species, yeasts such as Cryptococcus neoformans, and filamentous moulds such as Aspergillus fumigatus, have been shown to be implicated in biofilm-associated infections. Fungal biofilms have distinct developmental phases, including adhesion, colonisation, maturation and dispersal, which are governed by complex molecular events. Recalcitrance to antifungal therapy remains the greatest threat to patients with fungal biofilms. This review discusses our current understanding of the basic biology and clinical implications associated with fungal biofilms.

In Vitro Interaction between Alginate Lyase and Amphotericin B against Aspergillus fumigatus Biofilm Determined by Different Methods

“…Biofilms, likely the preferred growth form of fungi (1), exhibit profound resistance to many antimicrobial agents, thereby representing an escalating problem in the context of human health (8). First, the activities of both AMB and LAMB against a series of clinical A. fumigatus isolates, mostly derived from cases of invasive pulmonary infection, were determined (29).…”

“…This growth phenotype, which complies with the definition of a biofilm (10), may help A. fumigatus to colonize the host substratum and to resist phagocytic and antimicrobial attacks, mimicking the typical Candida albicans or bacterial biofilm (8,11). Recent observations have consistently shown that all antifungal drugs are significantly less effective when A. fumigatus is grown as a biofilm than when it is grown in the planktonic state (4,7,9,12,13), presumably as a reflection of multiple resistance mechanisms, including the ECM, which would prevent drug diffusion by acting as a physical barrier (14).…”

“…S imilar to biofilm-forming bacteria or yeasts (1), Aspergillus fumigatus, the most prevalent airborne fungal pathogen (2), is now largely acknowledged to be an organism able to grow and develop as a multicellular community (3), in which the hyphae are cohesively bonded together by a hydrophobic extracellular matrix (ECM) (4), under the aerial and static conditions found by the fungus either in vitro or in vivo (5)(6)(7)(8)(9). This growth phenotype, which complies with the definition of a biofilm (10), may help A. fumigatus to colonize the host substratum and to resist phagocytic and antimicrobial attacks, mimicking the typical Candida albicans or bacterial biofilm (8,11).…”

Sensing of mammalian IL-17A regulates fungal adaptation and virulence

“…As both adhesion and hyphal growth are considered to be important for pathogenicity 24 , we assessed whether the increased fungal adhesion and filamentation induced by IL-17A might have biological relevance in vivo. For this purpose, we evaluated whether binding to IL-17A could be demonstrated on fungi in vivo, the consequences in terms of fungal growth and morphology, and the involvement of the CRH family proteins.…”

Biofilm formation by zygomycetes: quantification, structure and matrix composition

“…Although filamentous fungi often penetrate the substrates that they grow on, and this invasive growth may not accurately represent the term biofilm (Harding et al, 2009), the yeasts Candida albicans and Trichosporon asahii have been shown to require differentiation to hyphal forms during biofilm formation (Harding et al, 2009;Ramage et al, 2009). Filamentation in fungi may therefore be a prerequisite for robust biofilm development and virulence, and fungal biofilms perhaps represent much more than a mere biological coating (Harding et al, 2009).…”