The PLEX-ID system is a novel technology that couples PCR amplification and electrospray ionization-mass spectrometry to identify pathogens directly in clinical specimens. The analytical performance of the PLEX-ID Broad Fungal assay was compared with that of traditional culture identification by using 91 characterized fungal culture isolates (64 manufacturer-claimed and 27 nonclaimed organisms) and directly by using 395 respiratory specimens. Discordant results were resolved by D2 large-subunit ribosomal DNA fungal sequencing. Environmental studies were performed to monitor for potential contamination. The PLEX-ID Broad Fungal assay correctly identified 95.6% (87/91) and 81.3% (74/91) of the culture isolates to the genus and species levels, respectively. Of the manufacturer-claimed organisms, 100% (64/64) and 92.2% (59/64) were correctly identified to the genus and species levels, respectively. Direct analysis of respiratory specimens resulted in 67.6% (267/395) and 66.6% (263/395) agreement with culture results to the genus and species levels, respectively, with 16.2% (64/395) of the results discordant with culture and 16.2% (64/395) not detected by the system. The majority (>95%) of the isolates not detected directly by the PLEX-ID system ultimately grew in low quantities in culture (<20 colonies). In 20.3% (35/172) of the respiratory specimens where no growth was observed in culture, the PLEX-ID system identified a fungus, suggesting a potential increase in sensitivity over culture in some instances. The PLEX-ID system provides a rapid method for the detection of a broad array of fungi directly in respiratory specimens and has the potential of impacting turnaround times and patient care by reducing the need to wait for the growth of an organism in culture.
Invasive fungal infections (IFIs) have increased in parallel with the escalating number of immunosuppressed patients seen in health care facilities over the past several decades. IFIs are a major cause of morbidity and mortality in high-risk populations, including those individuals who are at the extremes of age, who are undergoing solid organ or hematopoietic stem cell transplantation, who are undergoing prescribed immunosuppressive therapy, or who have an immunosuppressive disease (e.g., AIDS) (1). The most common fungal causes of IFIs are Candida species, Aspergillus species, and Cryptococcus species. However, the spectrum of fungal agents causing IFIs has broadened to include more atypical agents, including opportunistic yeasts (e.g., Trichosporon species and Rhodotorula species), the mucormycetes (e.g., Lichtheimia, Rhizopus, and Mucor species), the hyalohyphomycetes (e.g., Fusarium and Scedosporium species), the phaeohyphomycetes (e.g., Alternaria, Scedopsorium, and Bipolaris species), and the causes of endemic mycoses (e.g., Histoplasma capsulatum, Blastomyces dermatitidis, and Coccidioides immitis/C. posadasii) (1, 2). Early diagnosis and prompt therapy of IFIs are instrumental in the successful treatment of immunosuppressed populations, but convent...