Fluorescent staining for the rapid diagnosis of rare invasive fungal infections

Objective To evaluate the performance of an enhanced fluorescent staining for the rapid diagnosis of invasive mycosis, especially rare cases, considering the traditional culture method always leads to delays in clinical diagnosis for its time consuming. Methods Cases of invasive mycosis identified by fluorescent staining in our hospital from September, 2017 to September, 2018 were retrospectively analyzed. Three rare invasive infections were reported in this study. Clinical specimens were pretreated using standard procedures and then smeared on slides along with the enhanced fluorescent dye. Species of the pathogens were identified according to their morphology under fluorescent microscope. The traditional culture method was used as a standard method to identify the pathogenic species based on their colony morphology, followed by PCR and sequencing analysis for further confirmation. Results Three cases of invasive mycosis caused by rare pathogens of Talaromyces marneffei, Mucorales and Prototheca were rapidly diagnosed with the fluorescent staining method. Sequencing results indicated the species were Talaromyces marneffei, Rhizopus arrhizus and Prototheca wickerhamii. Conclusions Fluorescent staining is a rapid, economic and direct method for the diagnosis of invasive mycosis. The morphology of fungi is clear and easy to identify after fluorescence staining, which could be used for indicative diagnosis of highly suspected invasive mycosis and serve as an important complement to the traditional culture method, especially for the diagnosis of rare or uncultured fungal pathogens. Key words: Fluorescent staining; Rare fungus; Rapid diagnosis