Candida albicans Mycofilms Support Staphylococcus aureus Colonization and Enhances Miconazole Resistance in Dual-Species Interactions

Abstract

Polymicrobial inter-kingdom biofilm infections represent a clinical management conundrum. The presence of co-isolation of bacteria and fungi complicates the ability to routinely administer single antimicrobial regimens, and synergy between the microorganisms influences infection severity. We therefore investigated the nosocomial pathogens Staphylococcus aureus and Candida albicans with respect to antimicrobial intervention. We characterized the interaction using biofilm assays and evaluated the effect of miconazole treatment using in vitro and in vivo assays. Finally, we assessed the impact of biofilm extracellular matrix (ECM) on these interactions. Data indicated that the C. albicans mycofilms supported adhesion and colonization by S. aureus through close interactions with hyphal elements, significantly increasing S. aureus biofilm formation throughout biofilm maturation. Miconazole sensitivity was shown to be reduced in both mono- and dual-species biofilms compared to planktonic cells. Within a three-dimensional biofilm model sensitivity was also hindered. Galleria mellonella survival analysis showed both enhanced pathogenicity of the dual-species infection, which was concomitantly desensitized to miconazole treatment. Analysis of the ECM revealed the importance of extracellular DNA, which supported the adhesion of S. aureus and the development of the dual-species biofilm structures. Collectively, these data highlight the clinical importance of dual-species inter-kingdom biofilm infections, though also provides translational opportunities to manage them more effectively.

Fungi at the Scene of the Crime: Innocent Bystanders or Accomplices in Oral Infections?

“…This mechanism, which was dependent on the fungal adhesin ALS3, resulted in recovery of the bacteria from kidney tissue, whereas no recovery was observed in single-species infection. This mechanism is likely responsible for the increased pathogenicity of co-infection observed in vivo [79,80]. Synergised recalcitrance to antimicrobials has also been observed in several studies [80, 81, 82••].…”

“…More recently, the precise mechanism of this resistance has been elucidated, with a suggestive "barrier mechanism," whereby S. aureus coats itself in secreted C. albicans matrix molecules to impede drug penetration within the biofilm [82••]. Reciprocal resistance has also been observed against miconazole, a dual-active antifungal routinely used in angular cheilitis infections [80].…”

“…This relationship certainly appears to benefit S. aureus, and whether it coerces C. albicans by peer pressure to contribute to its success is debatable. We propose that S. aureus uses C. albicans as a physical scaffold, forming biofilms upon the 3-D hyphal biofilm network, an interaction we term mycofilms [80]. To date, it remains unclear how Candida benefits from the relationship, or whether it is just an unwitting accomplice.…”

Candida auris phenotypic heterogeneity determines pathogenicity in vitro

“…Following incubation, biofilms were washed gently once in PBS to remove any non-adhered cells. The biomass of each biofilm was determined via 0.05% crystal violet (CV) staining as described previously [19]. Absorbance of the CV stain was measured spectrophotometrically at 570nm in a microtiter plate reader (FLUOStar Omega, BMG Labtech, UK).…”

Interkingdom microbial consortia mechanisms to guide biotechnological applications

“…2). These are also present in interkingdom consortia (Agapakis et al, 2012;Stal, 2012) but with more variety, complexity and possibilities for interaction (Flemming and Wingender, 2010;Scherlach et al, 2013;Kean et al, 2017). Consortia can physically interact via aggregation (e.g.…”