Clinical impact of molecular identification of rare yeasts and nonsporulating molds recovered in culture from clinical specimens

Uncommon fungi can cause opportunistic infections and are often unidentifiable using phenotypic methods. Molecular techniques, like DNA sequencing, may permit species-level identification but results may be challenging to interpret. To determine the clinical impact of molecular identification in this setting, we performed a retrospective review of fungal isolates referred for molecular identification. Seventy-five distinct fungal species were identified from 93 referred isolates, 31 (41%) of which are not known to be human pathogens. DNA sequencing prompted change in anti-infective therapy in only 3 (3.5%) cases but significantly delayed culture turnaround time (40 ± 31 vs. 30 ± 13 days, P < 0.001). Patient immune status and concurrent histologic or serologic testing significantly correlated with the proportion of pathogenic isolates recovered and patients treated (χ², P < 0.05). Molecular identification of uncommon fungal isolates should be limited to specialized clinical settings such as patients with immunosuppression and/or concurrent positive histology or fungal serology.