New microbiological techniques for the diagnosis of invasive mycoses caused by filamentous fungi

Invasive mycoses have assumed great importance in recent years. Most infections are caused by Candida spp. but the emergence of fungal infections caused by Aspergillus spp. and other filamentous fungi is changing the spectrum of these diseases. Immunosuppression and the breakdown of anatomical barriers are the major risk-factors for fungal infections. Patients more prone to suffer invasive mycoses are found in various clinical settings, including haematology services, transplantation, oncology and intensive care units. The most serious infections afflict patients with haematological malignancy and prolonged and profound neutropenia. These patients have non-specific symptoms that make diagnosis very difficult. The recovery of fungi from blood, as well as other deep clinical specimens, remains an insensitive marker for the diagnosis of invasive mycoses. Antigen assays, e.g., (1 → 3)-β-D-glucan (BG) and galactomannan (GM) detection, are undergoing clinical validation. BG may be present in the blood of patients with infections caused by a wide variety of fungi, including Candida, Aspergillus and Fusarium. GM may be detected in blood very early in the course of invasive aspergillosis and be positive prior to the clinical suspicion of infection. However, the aetiology of GM false-positives has still to be completely elucidated. DNA detection by PCR is under investigation, and tests will require adaptation and validation before clinical use.