When Should Clinical Mycology Laboratories Perform Antifungal Susceptibility Testing? Revisiting Practice Through the Lens of Intrinsic Resistance

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Lass-Flörl C., ARIKAN AKDAĞLI S.

Mycopathologia, vol.191, no.1, 2026 (SCI-Expanded, Scopus) identifier identifier

  • Publication Type: Article / Article
  • Volume: 191 Issue: 1
  • Publication Date: 2026
  • Doi Number: 10.1007/s11046-025-01033-6
  • Journal Name: Mycopathologia
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, BIOSIS, Environment Index
  • Keywords: Acquired resistance, Fungi, Intrinsic resistance, Natural resistance, Resistance
  • Hacettepe University Affiliated: Yes

Abstract

Background: Antifungal susceptibility testing (AFST) guides therapy for invasive and refractory fungal infections, but routine testing of species with predictable, species-level (intrinsic) resistance can waste laboratory resources. Methods: Narrative synthesis of guideline documents and recent literature to define intrinsic resistance, summarize major fungal examples, and propose a selective AFST framework. Results: Key taxa show intrinsic non-susceptibility (e.g., Pichia kudriavzevii to fluconazole; Mucorales to short-tailed azoles; Cryptococcus spp. to echinocandins). Terminology differences between EUCAST and CLSI are noted. Recommended AFST is targeted to invasive/rare pathogens, treatment failure, surveillance, outbreak investigation, and evaluation of novel agents. Conclusion: A selective AFST strategy, reserving routine testing for species with variable or emergent resistance, enhances laboratory efficiency and antifungal stewardship while ensuring appropriate clinical therapy.