Diagnosis of invasive aspergillosis and mucormycosis in immunocompromised patients by seminested PCR assay of tissue samples.

Aspergillosis and mucormycosis are the most common mold infections in patients with hematological malignancies. Infections caused by species of the genus Aspergillus and the order Mucorales require different antifungal treatments depending on the in vitro susceptibility of the causative strain. Cultures from biopsy specimens frequently do not grow fungal pathogens, even from histopathologically proven cases of invasive fungal infection. Two seminested PCR assays were evaluated by amplifying DNA of zygomycetes and Aspergillus spp. from organ biopsies of 21 immunocompromised patients. The PCR assays correctly identified five cases of invasive aspergillosis and six cases of mucormycosis. They showed evidence of double mold infection in two cases. Both assays were negative in five negative controls and in two patients with yeast infections. Sequencing of the PCR products was in accordance with culture results in all culture-positive cases. In six patients without positive cultures but with positive histopathology, sequencing suggested a causative organism. Detection of fungal DNA from biopsy specimens allows rapid identification of the causative organism of invasive aspergillosis and mucormycosis. The use of these PCR assays may allow guided antifungal treatment in patients with invasive mold infections.