Utility of <scp>MALDI</scp>‐<scp>ToF MS</scp> for Recognition and Antifungal Susceptibility of <i>Nannizzia</i>, an Underestimated Group of Dermatophytes
Bibliographic record
Abstract
BACKGROUND: Geophilic Nannizzia dermatophytes are increasingly implicated in stubborn skin, hair, and nail infections, yet MALDI-TOF MS evaluations and antifungal-susceptibility data have focused almost exclusively on N. gypsea. Biochemical profiles and MICs cut-offs are limited. OBJECTIVES: To benchmark two commercial MALDI-TOF MS libraries and to determine in vitro activity of eight antifungals against a genus-wide panel of Nannizzia species. METHODS: One-hundred-and-three ITS-confirmed isolates representing 12 species were grown on potato-dextrose agar (PDA) for 7-14 days. Spectra were acquired with (i) the MSI-2 Dermatophyte Library after 4-14 days' PDA incubation (100 cultures) and (ii) the Bruker MALDI Biotyper Filamentous-Fungi Library 6.0/2023 after ≤ 3 days' growth in Sabouraud-dextrose broth (SDB) (73 cultures). BCCM/IHEM strains could not be evaluated on the Biotyper because of licence restrictions, leaving 73 non-duplicate isolates for direct MSI-2 vs MBT comparison. EUCAST E.Def 11.0 micro-broth dilution determined MICs for eight agents. RESULTS: MSI-2 achieved its highest accuracy with PDA day-7 cultures (45/73, 62%), whereas the liquid Biotyper protocol yielded 49/73 correct identifications (67%) within four days. Accepting low-confidence scores (≥ 1.7) from either library increased overall accuracy to 73%. MSI-2 remained superior for N. gypsea (73%) and uniquely detected N. nana (50%), which is absent from the current Biotyper release. Conversely, the Biotyper outperformed MSI-2 for N. incurvata, N. fulva, and N. praecox. Six very rare species (N. lorica, N. aenigmatica, N. corniculata, N. duboisii, N. perplicata, N. polymorpha) were not recognised by either database. Terbinafine displayed the lowest geometric mean MIC (0.009 mg/L); fluconazole and griseofulvin showed the highest values, and one US N. fulva isolate exhibited elevated itraconazole/voriconazole MICs (1 mg/L). CONCLUSIONS: Diagnostic coverage of Nannizzia remains incomplete. Expanding commercial MALDI-ToF MS libraries with spectra from rare species and performing routine susceptibility testing are essential to optimise patient management.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".