Reports of infections with the emerging fungal pathogen Candida auris first started in 2009. The pathogenic fungus—most notable for causing healthcare-associated outbreaks—is associated with infections arising from persistent surface and skin colonization. It is also challenging to work with, difficult to identify using traditional biochemical methods, and has been found to be resistant to all three major classes of antifungal medications.
Now, a previously uncharacterized adhesin protein specific to C. auris has been found to play a crucial role in the fungus’s ability to colonize a variety of living and non-living surfaces, and in its virulence.
This work is published in Science in the paper, “A Candida auris–specific adhesin, SCF1, governs surface association, colonization, and virulence.”
“These findings offer insight into the genetics and molecular mechanisms by which [this fungus] mediates surface association, a trait critical to the increasing disease burden of this emerging pathogen,” wrote the authors.
Since its discovery, C. auris has become increasingly responsible for life-threatening infections in healthcare facilities worldwide. Outbreaks of the multidrug-resistant pathogen are usually characterized by persistent colonization of patient skin and abiotic surfaces, including those of medical devices, which can remain positive for long periods and become intractable sources of contaminative transmission. This ability to colonize a wide range of surfaces is central to its emergence as a concerning threat to global health.
For fungal pathogens to attach to and colonize a surface, they rely on cell surface-exposed adhesin proteins. Although C. auris encodes genes similar to conserved adhesin families found in other Candida species, it’s unclear what gives C. auris its unique ability to colonize long-term on such a wide range of biotic and abiotic surfaces.
In this study, researchers characterized adhesins produced by C. auris and explored the basis of adhesion across 23 isolates from all five clades of the species.
In addition to conserved adhesins resembling those in other Candida species, they discovered a previously uncharacterized adhesin—Surface Colonization Factor (SCF1)—which was dominant and specific to C. auris. Unlike other fungal adhesins, which function through hydrophobic interactions, SCF1 relies on cationic interactions for surface attachment.
More specifically, the authors noted that SCF1 adheres “by cation-dependent interactions to a wide range of biotic and abiotic surfaces. Together with a complementary Candida adhesin, IFF4109, which attaches by hydrophobic interactions, these adhesins mediate colonization and biofilm formation.”
The authors showed that SCF1, in addition to the conserved adhesin IFF4109, are the principal mediators of biofilm formation, long-term surface colonization of skin and medical devices, and virulence in systemic infection.