A neutropenic bone marrow transplant patient has serial serum Galactomannan (GM) testing. On day 14 post-transplant, the GM index rises from 0.3 to 1.6 on ELISA (cut-off ≥0.5 for single test in BMT; ≥0.7 for serial monitoring). CT chest shows a new nodule. GM is a cell wall component released during active growth of which fungal genus?
- A Candida
- B Mucor
- C Aspergillus ✓
- D Cryptococcus
Explanation
Galactomannan (GM) is a polysaccharide component of the Aspergillus cell wall, released into the bloodstream during active hyphal growth in invasive aspergillosis. Serum GM ELISA (Platelia Aspergillus, Bio-Rad) is used for early non-invasive diagnosis in high-risk patients (haematological malignancy, HSCT). The test has high sensitivity in BMT/neutropenic patients but lower sensitivity in solid organ transplant recipients and patients on mould-active prophylaxis. False positives occur with piperacillin-tazobactam, other beta-lactams, and certain foods. Cryptococcus antigen is detected by latex agglutination or LFA for glucuronoxylomannan. Candida biomarkers include beta-D-glucan.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.