Multidrug Resistance Mechanisms in Fungal Systems

Multidrug resistance in fungal pathogens arises through a concerted array of biochemical and genetic adaptations that diminish the efficacy of existing antifungal agents. Central to this phenomenon is the overexpression of drug efflux pumps, notably those of the ATP-binding cassette (ABC) and major facilitator superfamily (MFS), which actively expel structurally diverse compounds. Alterations in drug targets, such as mutations in the lanosterol 14α-demethylase gene (ERG11/CYP51A), reduce drug binding, while compensatory changes in membrane sterol composition further impede antifungal uptake. Transcriptional regulators, including Zn2-Cys6 factors like Pdr1 in Candida glabrata, orchestrate the coordinated induction of resistance determinants. Signalling cascades, exemplified by calcineurin-mediated dephosphorylation events, integrate environmental cues to modulate these pathways. Biofilm formation and its associated extracellular matrix constitute an additional barrier, enhancing local drug sequestration and facilitating persister cell survival. Recent advances have also revealed that facilitated diffusion systems may influence azole uptake, suggesting that both import and export mechanisms contribute to clinical resistance. Together, these interlinked strategies underscore the adaptive plasticity of fungal pathogens and highlight the urgent need for novel therapeutic approaches that circumvent or disable these defence networks.

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Multidrug Resistance Mechanisms in Fungal Systems publication trend

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Technical terms

ATP-binding cassette (ABC) transporter: Membrane protein that uses ATP hydrolysis to expel a wide range of drugs from the cell.

Major facilitator superfamily (MFS) transporter: Proton-driven membrane carrier that exports antifungal agents and contributes to resistance.

Pdr1 transcription factor: A Zn2-Cys6 regulatory protein in Candida glabrata that coordinates expression of efflux pump genes.

Calcineurin: Calcium-activated serine/threonine phosphatase that modulates antifungal susceptibility via dephosphorylation of key regulators.

ERG11/CYP51A: Gene encoding lanosterol 14α-demethylase, the primary target of azole antifungals; mutations confer reduced drug affinity.

Biofilm: Structured microbial community embedded in an extracellular matrix that impedes antifungal penetration and fosters persistent infection.

Facilitated diffusion: Carrier-mediated transport mechanism that allows passive uptake of azoles into fungal cells via specific transporters.

References

1. The role of the Mediator complex in fungal pathogenesis and response to antifungal agents. Essays in Biochemistry (2023).
2. Calcineurin is required for Candida glabrata Pdr1 transcriptional activation. mBio (2023).
3. Azole Drugs Are Imported By Facilitated Diffusion in Candida albicans and Other Pathogenic Fungi. PLOS Pathogens (2010).
4. ABC Transporter Genes Show Upregulated Expression in Drug-Resistant Clinical Isolates of Candida auris: A Genome-Wide Characterization of ATP-Binding Cassette (ABC) Transporter Genes. Frontiers in Microbiology (2019).