BOSTON — In situ hybridization may provide a much faster method of diagnosing dimorphic fungal infections than tissue culturing, Jared J. Abbott, M.D., reported at the annual meeting of the American Society of Dermatopathology.
Although tissue culturing is considered the preferred diagnostic method in current practice, it takes time to complete. Often, tissue cultures are not done, said Dr. Abbott, a resident in pathology at the Mayo Clinic, Rochester, Minn.
Cutaneous fungal infections can be the presenting sign of a systemic infection, and thus the skin infection can be secondary. The prognosis of cutaneous fungal infections is heavily dependent on timely diagnosis and treatment, he said in a poster presentation.
Dr. Abbott and his colleagues diagnosed cutaneous infections of dimorphic fungi (histoplasmosis, blastomycosis, coccidiomycosis, or cryptococcosis) in five patients, four of whom were immunocompromised. Within 36-48 hours, in situ hybridization gave the same results as tissue culturing for all patients.
The investigators determined the presence of dimorphic fungi in all of the skin sections via morphology, but none of the organisms were diagnostically discernible.
The in situ hybridization method used by Dr. Abbott and his associates detected fungal ribosomal RNA elements in paraffin-embedded tissue using labeled, single-stranded DNA oligonucleotide probes.
“In situ hybridization has a potential role in distinguishing between organisms of similar morphology in cutaneous fungal infections,” the investigators concluded.