In Aspergillus fumigatus invasive infection in neutropenic patients, galactomannan (GM) antigen detection in serum is used for early diagnosis. The galactomannan antigen is a component of:
- A Cell wall beta-1,5-linked galactofuranose side chains on mannan backbone, released during active hyphal growth ✓
- B Melanin pigment in the conidial cell wall
- C Secreted phospholipase during tissue invasion
- D Gliotoxin immunosuppressive toxin released in blood
Explanation
Galactomannan is a cell wall polysaccharide of Aspergillus spp. consisting of a mannan backbone with beta-1,5-linked galactofuranose side chains; it is released into blood and body fluids during active invasive hyphal growth and tissue invasion. The sandwich ELISA (Platelia Aspergillus, Bio-Rad) detects GM with sensitivity ~70-80% and specificity ~85-90% in neutropenic patients; a GM index ≥0.5 ODI (optical density index) on two consecutive samples is diagnostic per EORTC criteria. Melanin is a conidial virulence factor. Phospholipase and gliotoxin are secreted virulence factors but are not detected by galactomannan assay.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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