TABLE 1.
Identification of clinical yeast isolates by API kits or the combination of CMA plus CTA, including growth characteristics on these media
| Species (no. of strains) | Colony characteristics on CMA | Morphologic features on CTA | Identification with CMA plus CTA | Identification by API 20C AUX or API 32C system |
|---|---|---|---|---|
| C. albicans (50) | Apple green colonies; consistent distinctive appearance | Chlamydospores present, although >2 days required for some strains; abundant pseudohyphae, some true hyphae, clusters of blastospores along pseudohyphae; distinctive appearance | Accurate identification with both | Identified one strain as C. parapsilosis |
| C. glabrata (116) | Large pale pink to purple glossy colonies | No pseudohyphae or hyphae; yeast cells are ∼2.5 × 4 μm; consistent distinctive appearance | Accurate identification, morphology essential | Identified all strains as C. glabrata |
| C. tropicalis (87) | Dull blue, sometimes pink, colonies; all developed purple halo of pigment that diffused into surrounding agar; distinctive appearance | Abundant pseudohyphae often radiating with clusters of blastoconidia at the center; variable appearance | Accurate identification with CMA | Identified all strains as C. tropicalis |
| C. krusei (6) | Large, flat, spreading, pale pink colonies with matt surfaces; distinctive appearance | Extensive branched pseudomycelium with chains of elongate cells giving tree-like appearance; clusters and chains of blastospores along pseudohyphae; consistent distinctive appearance | Accurate identification with both | Strains identified as C. krusei with 50% confidence |
| C. parapsilosis (47) | Off-white to pale pink colonies; variable appearance | Branched chains of elongated cells with clusters of blastospores along them; occasional giant cells; variable appearance | Not always able to identify | Identified all strains as C. parapsilosis |
| C. guilliermondii (5) | Small pink to purple colonies; variable appearance | Pseudohyphae with clusters of blastospores; variable appearance | Not always able to identify | API 32C identified strains with 53.7% confidence |
| C. dubliniensis (1) | Dark green colonies | Abundant chlamydospores present; abundant pseudohyphae, some true hyphae, clusters of blastospores along pseudohyphae | Identification with both for the strain examined | Not in API database; identified as Candida sake with low confidence |
| Trichosporon spp. (37) | Tiny, rough, dry-looking, dirty blue-to-grey colonies, distinctive appearance | Pseudomycelium and abundant true mycelium breaking up into arthrospores; distinctive appearance | Accurate identification with both | Identified all strains as T. beigelii |
| C. neoformans (2) | Pink colonies, sometimes mucoid | No pseudohyphae or hyphae; Large spherical yeast cells ∼3–7.5 μm in diameter; distinctive appearance | Accurate identification, morphology essential | Identified as C. neoformans |
| S. cerevisiae (2) | Small purple colonies | Oval cells with very short multilateral budding | Accurate identification of strains examined, morphology essential | Identified one strain as Cryptococcus laurentii |
| P. wickerhamii (1) | Large, variably sized spherical cells, some containing sporangia; distinctive appearance | Large, variably sized spherical cells, 2–16 μm, some containing sporangia; distinctive appearance | Accurate identification, morphology essential | Not in API database; identified the strain as C. glabrata |