Differentiation of Fusarium From Aspergillus Species by Colorimetric In Situ Hybridization in Formalin-Fixed, Paraffin-Embedded Tissue Sections Using Dual Fluorogenic-Labeled LNA Probes

Fusarium and Aspergillus are 2 genera of fungal pathogens that can result in devastating disease particularly in immunosuppressed hosts. In tissue sections, these organisms can be extremely difficult to distinguish from one another. To differentiate between these 2 pathogens, a rapid (<3 hours) ribosomal RNA (rRNA) in situ hybridization (ISH) protocol using dual, fluorogenic-labeled oligonucleotide probes composed of a mixture of DNA and locked nucleic acids (LNAs) was developed. This assay was able to differentiate between Aspergillus and Fusarium in formalin-fixed paraffin-embedded tissue sections. ISH targeting rRNA can be used to identify the species of fungal pathogens in surgical pathology material and may be useful when pathogens are histologically observed but cultures are negative or have not been performed. ISH with dual-labeled LNA probes may be useful for detecting a variety of fungal pathogens in formalin-fixed paraffin-embedded tissue specimens.