Significance of Molecular Identification and Antifungal Susceptibility of Clinically Significant Yeasts and Moulds in a Global Antifungal Surveillance Programme

The increasing diversity of opportunistic fungi causing serious invasive fungal infections (IFI) has been documented. Accurate identification (ID) is important in guiding therapy, determining prognosis for IFIs and in epidemiological surveys. We assessed the utility of PCR-based methods for the ID of yeasts and moulds that either were uncommon, failed conventional ID, or represented unusual biochemical or phenotypic profiles of common species. Among 1,790 viable fungal clinical isolates received during the SENTRY Program in 2010, 322 strains from 40 study sites had ID confirmed by molecular methods. Isolates were previously identified in participant institutions. Yeasts that were not confirmed by morphology on CHROMagar, growth at 45 °C (Candida albicans/dubliniensis), or assimilation of trehalose (C. glabrata) as well as non-Candida yeasts and all moulds were amplified and sequenced using primers amplifying one or more of the following genes: ITS, 28S, β-tubulin (Aspergillus spp.), TEF (Fusarium spp.), IGS (Trichosporon spp.). The isolates selected for molecular ID included 149 isolates of Candida species, 77 of Aspergillus species, 73 non-Candida yeasts, and 23 other moulds (a total of 41 different species). Overall, the ID determined by the submitting site was confirmed for 189 isolates (58.7 %): Aspergillus spp. (64.1 % correct); Candida spp. (60.1 % correct); non-Candida yeasts (58.9 % correct); non-Aspergillus moulds (30.4 % correct). Species with high levels of concordance between conventional and molecular ID included A. fumigatus (95.0  %), C. lusitaniae (100 %), C. dubliniensis (92.3 %), C. kefyr (100 %), and C. neoformans (90.2 %). Only 50.0 % of isolates of C. albicans and 59.1 % of C. glabrata selected due to unusual phenotypic or biochemical features were found to be correctly identified by the submitting site. Molecular methods for the identification of fungal pathogens are an important adjunct to the conventional identification of many less common clinically relevant yeasts and moulds including species of Candida with unusual or erroneous phenotypic or biochemical profiles. Molecular confirmation of fungal identification is essential in epidemiological surveys such as SENTRY.