T he newly emerging multidrug-resistant yeast Candida auris can cause serious infections and may be underrepresented, as it can be misidentified as other species (e.g., Candida haemulonii, Candida duobushaemulonii, or Saccharomyces cerevisiae) by some biochemical-based testing systems (1-4). Candida auris can be identified using research use only (RUO) libraries on matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) platforms, such as the Biotyper platform (Bruker, Billerica, MA), but may need labor-intensive full-tube extraction procedures (3-5). Our laboratory uses the Biotyper equipped with both FDA-approved and RUO libraries. The RUO library contains three C. auris entries, but the identification of C. auris remains a challenge, and some isolates are never identified by the system. To improve the identification, a novel database, "CMdb," was developed and evaluated on our two Biotyper systems. The CMdb was created using internationally collected yeasts from the CDC (6) and one in-house clinical C. auris isolate. Bruker's protocol was used for database creation, and the direct on-plate extraction method was used for target preparation (7). The CMdb was evaluated on 23 clinical C. auris isolates, 20 CDC strains, 52 isolates of 10 other yeast species, and 28 isolates of 16 bacterial species.

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Histochemical staining, beta-glucuronidase (GUS) activity, or placing roots on agar were methods used to characterize interactions between the pathogenic fungus, Fusarium oxysporum f. sp. lycopersici, and the nonpathogenic biocontrol F. oxysporum strain 70T01 with respect to colonization behaviors, interaction sites, and population densities on tomato roots. Mycelia of strain 70T01, a genetic transformant expressing stable GUS activity, hygromycin B resistance, and effective disease control, were localized in epidermal and cortex cell layers of tomato roots in a discontinuous and uneven pattern. In contrast, mycelia of F. oxysporum f. sp. lycopersici were found in the vascular bundles. Thus, direct interactions between the two fungi likely happen in the root surface cell layers. Colonization density of strain 70T01 was related to the inoculation density but decreased with distance from the inoculation site. Host defense reactions, including increased cell wall thickness or papilla deposits, were adjacent to 70T01 hyphae. Experiments done in soil showed that strain 70T01 densities in roots were highest at inoculation zones and barely detectable for root segments more than 2 cm away from the inoculation sites. F. oxysporum f. sp. lycopersici densities were lowest at 70T01 inoculation zones and highest (>10 times) where strain 70T01 was not directly applied. Newly elongating roots where strain 70T01 did not reach were available for infection by the pathogen. The higher strain 70T01 density was always found when the plants were simultaneously infected by F. oxysporum f. sp. lycopersici, suggesting that F. oxysporum f. sp. lycopersici has as much influence in predisposing the plant to colonization by strain 70T01 as strain 70T01 has on providing disease protection against the pathogen.