Comparison of Histopathological Analysis, Culture, and Polymerase Chain Reaction Assays to Detect Invasive Mold Infections from Biopsy Specimens.

Background. With the advent of new antifungal agents, the identification of a causative pathogen is crucial to guide the antifungal treatment of invasive mold infection. However, tissue cultures often fail to grow a fungal pathogen in cases of suspected mold infection. Methods. In a prospective multicenter study, we compared the results of histopathological analysis, culture, and 2 seminested polymerase chain reaction assays identifying Aspergillus species and Zygomycetes as causative agents of invasive mold infections using respiratory tract biopsy samples obtained from 56 immuno-compromised patients who had suspected mold infection. Results. Mold hyphae were detected histopathologically in 27 (48%) of the tissue specimens. Hyphae corresponded to either aspergillosis (n = 18) or zygomycosis (n = 6) or could not be further specified (n = 3). A mold was cultured from 14 of 18 samples with aspergillus hyphae, 2 of 6 samples with Zygomycetes hyphae, and 1 of 3 samples with unspecified hyphae. Polymerase chain reaction was superior to culture in detecting the infecting mold (26 of 27 samples vs. 17 of 27 samples, respectively; P = .006) from histopathologically positive samples. Genus or species identification by sequencing of the polymerase chain reaction products were in accordance with culture results in 16 of 18 culture-positive samples. Both polymerase chain reaction assays failed to detect fungal DNA in 1 sample that had unspecified hyphae and negative culture results. Conclusion. The PCR assays offer a reliable etiologic diagnosis that is superior to culture in patients with proven invasive mold infection. This may improve patient management through tailored antifungal therapy when cultures fail to grow a pathogen. [ABSTRACT FROM AUTHOR]