A New Duplex PCR-Assay for the Detection and Identification of Species.

Paracoccidioidomycosis (PCM) is a life-threatening systemic fungal infection caused by members of the complex and . Routine diagnoses of PCM down to the species level using classical mycological approaches are unspecific due to overlapping phenotypes. There is an urgent need for specific, sensitive, and cost-effective molecular tools to diagnose PCM. Variation among the exon-2 of the gp43 gene was exploited to design species-specific primer pairs to discriminate between members of the complex and in a duplex PCR assay. Primer-BLAST searches revealed highly species-specific primers, and no significant region of homology was found against DNA databases except for species. Primers PbraCx-F and PbraCx-R targeting DNA produced an amplicon of 308 bp, while primers Plu-F and Plu-R targeting DNA generated an amplicon of 142 bp. The lower limit of detection for our duplex PCR assay was 1 pg of gDNA. A panel of 62 revealed 100% specificity (AUC = 1.000, 95%CI 0.972-1.000, < 0.0001) without cross-reacting with other medically relevant fungi or human DNA. As a proof of concept, we demonstrated the accurate identification of the complex ( = 7) or ( = 6) from a broad range of formalin-fixed, paraffin-embedded (FFPE) tissues of PCM patient's organs. In four cases, FFPE PCR results confirmed, for the first time, co-infection due to (S1) and in the same biopsy. Our duplex PCR assay is useful to detect and differentiate members of the complex and , providing clinical laboratories with an important tool to be applied routinely, especially in atypical cases such as those featuring negative serology and positive mycological examination of clinical specimens as well as for the investigation of putative co-infection cases. This will likely benefit thousands of infected patients every year in a wide area of the Americas.