Paracoccidioides brasiliensis Molecular Detection by the Label-Free Colorimetric Method Using Gold Nanoparticles

Paracoccidioides brasiliensis (P. brasiliensis) is a thermo-dependent dimorphic fungus found in the environment as mycelia (~ 25 °C) also as yeast cells (~ 37 °C) in humans. This species is the etiologic agent of Paracoccidioidomycosis (PCM), a chronic granulomatous progressive disease that attacks skin, lungs, and other internal organs. The epidemiological data shows predominance of PCM in South American countries. Brazil itself has 80.0% of cases. This infection is responsible for 52.0% of deaths from Brazilian mycosis. Diagnosis can fail by cross-reaction with other diseases, high costs, and time-consuming procedures. The aim of this study is to identify the presence of P. brasiliensis using gold nanoparticles combined to pathogen specific GP43 or GP27 DNA sequences added to develop a rapid, low-cost label-free colorimetric diagnostic tool. The label-free colorimetric test was evaluated with 192 samples (96 positive and 96 negative). The receiver operating characteristic results suggest that the technique can identify P. brasiliensis effectively. The GP43 DNA sequences showed 100.0% sensitivity plus 96.0% specificity; GP27 showed 92.0% sensitivity plus 95.6% specificity. Development of such low-cost diagnostic methods will have great impact in remote endemic areas.