[Microbiological diagnosis of invasive mycosis]

The prognosis of invasive fungal infections (IFI) depends on the speed of diagnosis and treatment. Conventional diagnostic methods are of low sensitivity, laborious and too slow, leading to the need for new, faster, and more efficient diagnostic strategies. There are several techniques for diagnosing a candidemia that are faster than the conventional blood culture (BC). Once yeast growth in BC is detected, species identification can be speeded up by mass spectrometry (30minutes), commercialised molecular techniques (60-80minutes) or fluorescent in situ hybridization (90minutes). The combined detection of biomarkers (antimicellium, mannan and anti-mannan or β-glucan) has shown to be of greater use than their individual use. Commercialised nucleic acid amplification techniques (Septifast®, T2Candida®) are very reliable alternatives to BC. The detection of the capsular antigen of Cryptococcus, by means of latex agglutination or immuno-chromatography, is a valuable technique for cryptococcosis diagnosis. Direct microscopic examination and culture of representative specimens is used for the conventional diagnosis of IFI by filamentous fungi. Detection of galactomannan and β-glucan are considered diagnostic criteria for probable invasive aspergillosis and probable IFI, respectively, despite the lack of specificity of the latter. The detection of fungal volatile organic compounds in breath is an interesting diagnostic strategy in pulmonary infections. Although widely used, nucleic acid detection techniques are not considered diagnostic criteria for IFIs caused by moulds in consensus documents, due to their lack of standardisation. However, they are the only alternative to culture methods in invasive infections by Scedosporium/Lomentospora, Fusarium, zygomycetes, or dematiaceous fungi.