Background: The management of cerebral abscesses caused by dark-pigmented Fonsecaea monophora in healthy individuals continues to be challenging due to no consensus on the therapeutic regimen. Due to the absence of an accurate identification method, Fonsecaea species are often misidentified due to indistinct morphology features.
Materials and Methods: An F. monophora strain from an immunocompetent host with cerebral abscess was collected and identified by ITS rDNA molecular sequencing. The ITS sequences of the isolate were compared with that of the other ten Chinese F. monophora isolates obtained from GenBank for difference comparison and phylogenetic analysis. Fluorescence, Gram stains, and medan lactate were used to observe the colonial morphology. Antifungal susceptibility testing was implemented to demonstrate the antibiotic susceptibility profile. Galleria mellonella larvae were used as a model to study virulence of F. monophora . Medical records and clinical data of the patient were collected and analyzed.
Results: Antifungal susceptibility testing indicated that triazole antifungal drugs possess remarkable antifungal effect against F. monophora , and satisfactory antifungal effect of itraconazole was corresponding to the drug susceptibility results. Compared with the GM test, the serum G test was found to be more sensitive. The virulence and melanization in G. mellonella models for F. monophora were observed, and the death rates of infected larvae were positively related to injected concentrations of fungus. The phylogenetic tree was constructed from the ITS sequences of the clinical isolate along with ten Chinese F. monophora isolates, revealing that there is high relatedness in F. monophora strains collected from China.
Conclusion: F. monophora is an important neurotropic dematiaceous fungus and increasingly causing disease in immunocompetent individuals by means of noninvasive ways. Fungal culture, stainings, and molecular methods could be utilized to identify the etiologic agent. Triazole antifungal drugs can be applied as empiric therapeutic agents for phaeohyphomycosis.
Keywords: phaeohyphomycosis, Fonsecaea monophora , DNA sequence analysis, antifungal susceptibility testing