Abstract: Nucleic acid probes and molecular method to identify the varieties and genotypic groups within C. neoformans species complex. The method employs a flow cytometer with a dual laser system that allows the simultaneous detection of different target sequences in a multiplex and high-throughput format. The assay uses a liquid suspension hybridization format with specific oligonucleotide probes that are covalently bound to the surface of fluorescent color-coded microspheres. Biotinylated target amplicons, which hybridized to their complementary probe sequences, are quantified by the addition of the conjugate, streptavidin-R-phycoerythrin. The assay is specific and sensitive, and allows discrimination of 1 bp mismatch with no apparent cross-reactivity and is capable of detecting 101 to 103 genome copies. The assay can be used directly with yeast cells or isolated DNA, can be undertaken in less than one hour following PCR amplification and permits identification of species in a multiplex format.

Abstract: The emergence of opportunistic and antifungal resistant strains has given rise to an urgent need for a rapid and accurate method for the detection of fungal pathogens. In this application, we demonstrate the detection of medically important fungal pathogens at the species level. The present method, which is based on a nucleotide hybridization assay, consists of a combination of different sets of fluorescent beads covalently bound to species specific capture probes. Upon hybridization, the beads bearing the target amplicons are classified by their spectral addresses with a 635 nm laser. Quantitation of the hybridized biotinylated amplicon is based on the fluorescent detection with a 532 nm laser. Using this technology we designed and tested various multiplex formats, the performance of forty eight species specific and group specific capture probes designed from sequence analysis in the D1/D2 region of ribosomal DNA, internal transcribed spacer regions (ITS), and intergenic spacer region (IGS).