Antifungal Intrinsic Resistance Gating Module

Module antifungal_intrinsic_resistance_gating 0 disorders Pathograph 2

A conserved antifungal drug-choice-gating module representing the species-level intrinsic resistance that excludes whole antifungal classes a priori, before any susceptibility testing. Unlike the fungal drug-target modules (ergosterol synthesis, ergosterol-membrane binding, glucan-synthase, nucleic-acid antimetabolite), the nodes here are not a single druggable enzyme but a gating principle: the small antifungal armamentarium is sharply constrained by organism identity, because the target a class needs is absent, divergent, or non-viable in certain fungi. The paradigm cases are fixed by phylogeny — Aspergillus is intrinsically resistant to fluconazole (requiring a mold-active azole such as voriconazole or isavuconazole, or amphotericin B); Cryptococcus is intrinsically resistant to the echinocandins (the β-1,3-glucan-synthase target is present but not a viable drug target); and the Mucorales (mucormycosis) are intrinsically resistant to both voriconazole and the echinocandins, leaving amphotericin B or isavuconazole. Layered on top of this fixed intrinsic landscape, emerging multidrug-resistant species — most notably Candida auris — acquire resistance across the azoles, polyenes, and echinocandins simultaneously, further narrowing empiric options. This module encodes WHY empiric antifungal selection depends on organism identification rather than on "any antifungal," complementing the target-based modules that explain how a given drug works once a viable target exists.

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Pathophysiology Nodes

2 shared nodes are defined in this module.

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Cell Types

No cell types are annotated for this module.

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Biological Processes

Notes

This is an antifungal drug-mechanism (species-level gating) module, not a specific disease. It is the antifungal analog of the antibacterial intracellular_pathogen_persistence module: the nodes are gating principles, not enzyme targets. Disorder entries for mycoses reference nodes via conforms_to (e.g., "antifungal_intrinsic_resistance_gating#Species-Level Intrinsic Antifungal Resistance"), and their treatments may point at the gating node via target_mechanisms to record why a whole class is or is not an option. Key conformance / gating target: "Species-Level Intrinsic Antifungal Resistance" (the Aspergillus/fluconazole, Cryptococcus/echinocandin, Mucorales/voriconazole+ echinocandin exclusions). A conforming disease typically ALSO conforms to a target-based antifungal module (ergosterol synthesis, ergosterol-membrane binding, glucan synthase, or nucleic-acid antimetabolite) for the molecular mechanism of whatever drug remains viable, with this module explaining which classes are excluded a priori by the infecting species. See projects/ANTIFUNGAL.md (the antifungal_intrinsic_resistance_gating row of the proposed-module table and the "Intrinsic species resistance" axis), where this module is positioned as the species-level class-exclusion gate.

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Used By Disorder Entries

No disorder entries currently reference this module via conforms_to.

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Pathograph

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Pathophysiology

Species-Level Intrinsic Antifungal Resistance

intrinsic resistance

The species identity of the infecting fungus excludes whole antifungal classes before any susceptibility result, because the molecular target a class requires is absent, divergent, or non-viable in that organism. This is the central gating principle of the module and its canonical conformance / gating target. Three fixed, phylogeny-determined exclusions recur clinically: (1) Aspergillus species are intrinsically resistant to fluconazole, so invasive aspergillosis requires a mold-active azole (voriconazole, isavuconazole, posaconazole, itraconazole) or amphotericin B; (2) Cryptococcus species display negligible susceptibility to the echinocandins — the β-1,3-glucan-synthase target exists but is not a viable drug target — so cryptococcosis is treated with amphotericin B, flucytosine, and fluconazole, never an echinocandin; and (3) the Mucorales (agents of mucormycosis) are intrinsically resistant to both voriconazole and the echinocandins, leaving amphotericin B (typically lipid formulations) or isavuconazole as the only active options. Because these exclusions track monophyletic taxonomic groups, members of the same order behave alike, and empiric drug choice is therefore gated by organism identification rather than by in-vitro testing of the individual isolate.

Species-level intrinsic insusceptibility to the antifungal GO:0009410

Downstream

Acquired Multidrug Resistance in Emerging Species (Candida auris) On top of the fixed intrinsic-resistance landscape, emerging species acquire resistance across multiple classes simultaneously, further narrowing the already organism-gated options.

Acquired Multidrug Resistance in Emerging Species (Candida auris)

adaptive escape

Beyond the phylogenetically fixed intrinsic exclusions, a second gating layer arises from emerging pathogens that acquire resistance across several antifungal classes at once. The exemplar is Candida auris, an emerging multidrug-resistant species in which acquired resistance to the azoles, echinocandins, and polyenes can co-occur, collapsing the available armamentarium and forcing susceptibility-guided, often last-line therapy. More broadly, multidrug resistance to the azoles, echinocandins, and polyenes is increasingly reported across Candida species (notably C. glabrata and now C. auris), driven by overall antifungal use, subtherapeutic drug levels, and biofilm sequestration. This node captures why species identification must be coupled to surveillance of acquired resistance: an organism whose class is nominally available may nonetheless be untreatable with it, so empiric choice and stewardship must account for the emergence of pan-resistant strains.

Response to Xenobiotic Stimulus GO:0009410