Chromoblastomycosis by Fonsecaea: Infection routes, detection and therapy

Najafzadeh M.J., Vicente V.A., Sun J., De Hoog G.S.


Fonsecaea is one of the main agents of human chromoblastomycosis. The disease occurs worldwide, but most cases have been reported from tropical and subtropical climates. On the basis of ribosomal DNA internal transcribed spacer (ITS) sequence data, two species were recognized until recently, i.e., F. pedrosoi and F. monophora. Another, molecular sibling of F. pedrosoi, Fonsecaea nubica, was discovered using multilocus molecular data including AFLP profiles; recently F. multimorphosa was added, which however is not an agent of chromoblastomycosis. The general hypothesis is that agents of chromoblastomycosis gain entrance through the skin by traumatic implantation of contaminated material. This suggests that the etiological agents are environmental saprobes, and that the onset of disease is strictly coincidental. Particularly fungi growing on or in prickly plants, such as living Cactaceae and Mimosa have been discussed as sources of infection. We used from loop-mediated isothermal amplification (LAMP) and rolling circle amplification (RCA) for rapid detection and identification of Fonsecaea strains. LAMP is a powerful nucleic acid amplification technique that rapidly and accurately amplifies target DNA under isothermal conditions; we used this method for rapid screening of Fonsecaea and other Chaetothyriales. The second molecular identification technique that was established is RCA. This technique proved to be suitable for the identification of three Fonsecaea species. The simplicity, sensitivity, robustness and low costs make RCA an attractive technique for the reliable identification of sibling species and other closely related fungi. Therapy for chromoblastomycosis is challenging because there is no consensus regarding the treatment of choice. The in vitro activities of eight antifungal drugs against clinical isolates of Fonsecaea pedrosoi (n = 21), Fonsecaea monophora (n = 25), and Fonsecaea nubica (n = 9) were tested. The resulting MIC90s for all strains (n = 55) were as follows, in increasing order: posaconazole, 0.063 μg ml-1; itraconazole, 0.125 μg ml-1; Isavuconazole, 0.25 μg ml-1; voriconazole, 0.5 μg ml-1; amphotericin B, 2 μg ml-1; caspofungin, 2 μg ml-1; anidulafungin, 2 μg ml-1; and fluconazole, 32 μg ml-1.

    • ISHAM 18th (2012)