Abstract: Objectives To evaluate the applicability of in situ hybridization (ISH) technique in the specific diagnosis of clinical systemic Aspergillus infection. Methods Sixteen formalin fixed and paraffin embeded tissue specimens from patients with suspected Aspergillus spp. infection were studied by an ISH technique with a DNA probe representing fragment of alkaline proteinase gene, which was synthesized and digoxigenin labeled, by means of polymerase chain reaction (PCR). Results Positive staining was obtained in 13 tissue specimens from 16 patients with suspected systemic Aspergillus infection, but in none of the tissues infected with other fungi. Conclusions The ISH is a sensitive, specific technique for detecting systemic Aspergillus infection. As the DNA probe is known specific for Aspergillus fumigatus and has low homology with Aspergillus flavus, the ISH technique with this probe could differentiate the two common species from other Aspergillus spp. or from non Aspergillus fungi in tissue specimens. It could be applicable to clinical molecular diagnosis of Aspergillus infection.

Key words: DNA probes, In situ hybridization, Aspergillosis