Aspergillus niger growth on SDA
Table of Contents
| Finding | Likely Contaminant | Possible Colonizer | Likely Pathogen |
|---|---|---|---|
| Single isolate from 1 sample | ✅ | ✅ | ❌ |
| Repeated isolation from multiple properly collected samples | ❌ | ✅ | ✅ |
| Direct microscopy/tissue shows hyphae | ❌ | ❌ | ✅ |
| Sterile site growth + clinical symptoms | ❌ | ❌ | ✅ |
| Immunocompromised patient + radiologic signs + positive antigen/PCR | ❌ | ❌ | ✅ |
“In our cohort, Aspergillus niger was considered a true etiologic agent when repeatedly isolated from properly collected specimens, supported by compatible clinical findings, radiologic evidence, and direct demonstration of fungal hyphae in patient samples or tissues. Single, incidental isolates without supportive evidence were classified as probable contaminants or colonizers.”
| Step | Criteria | Interpretation |
|---|---|---|
| 1 | Specimen type — sterile site (e.g., urine from catheter, BAL, biopsy tissue) vs. non-sterile (expectorated sputum) | Sterile site growth → more likely pathogen |
| 2 | Repeat isolation — same patient, ≥2 separate samples, proper collection | Repeat positives → infection more likely |
| 3 | Direct microscopy (KOH/Calcofluor, histopathology) — septate hyphae with dichotomous branching seen | Positive microscopy → supports true infection |
| 4 | Clinical signs/symptoms — fever, cough, hemoptysis, urinary symptoms, organ-specific findings | Symptoms present → stronger evidence |
| 5 | Radiological correlation — chest CT (halo sign, nodules, cavitation), renal USG/CT (fungus ball) | Imaging consistent → increases probability |
| 6 | Serology/molecular — Galactomannan, β-D-glucan, Aspergillus PCR positive | Positive test → strong infection evidence |
| 7 | Immune status — neutropenia, hematologic malignancy, chemotherapy, transplant, corticosteroid use | Immunocompromised → higher infection risk |
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