CHROMagar Candida, a new differential isolation medium for presumptive identification of clinically important Candida species

Abstract

is a novel, differential culture medium that is claimed to facilitate the isolation and presumptive identification of some clinically important yeast species. We evaluated the use of this medium with 726 yeast isolates, including 82 isolated directly on the medium from clinical material. After 2 days of incubation at 37°C, 285 C. albicans isolates gave distinctive green colonies that were not seen with any of 441 other yeast isolates representing 21 different species. A total of 54 C. tropicalis isolates also developed distinctive dark blue-gray colonies with a halo of dark brownish purple in the surrounding agar. C. krusei isolates (n = 43) also formed highly characteristic rough, spreading colonies with pale pink centers and a white edge that was otherwise encountered only rarely with isolates of C. norvegensis. Trichosporon spp. (n = 34) formed small, pale colonies that became larger and characteristically rough with prolonged incubation. Most of the other 310 yeasts studied formed colonies with a color that ranged from white to pink to purple with a brownish tint. The only exceptions were found among isolates identified as Geotrichum sp. or Pichia sp., some of which formed colonies with a gray to blue color and which in two instances formed a green pigment or a dark halo in the agar. The specificity and sensitivity of the new medium for the presumptive identification of C. albicans, C. krusei, and C. tropicalis exceeded 99%o for all three species. A blinded reading test involving four personnel and 57 yeast isolates representing nine clinically important species confirmed that colonial appearance after 48 h of incubation on CHROMagar Candida afforded the correct presumptive recognition of C. albicans, C. tropicalis, C. krusei, and Trichosporon spp. None of nine bacterial isolates grew on CHROMagar Candida within 72 h, and bacteria (Escherichia coli) grew from only 4 of 104 vaginal, 100 oral, and 99 anorectal swabs. The new medium supported the growth of 19 of 23 dermatophyte fungi tested and 41 of 43 other molds representing a broad range of fungal pathogens and contaminants. In parallel cultures of 348 clinical specimens set up on Sabouraud agar and CHROMagar Candida, both media grew yeasts in the same 78 instances. CHROMagar Candida is recommended as a useful isolation medium capable of the presumptive identification of the yeast species most commonly isolated from clinical material and facilitating recognition of mixed yeast cultures.

In vitro and clinical evaluation of specific dentifrices for complete denture hygiene

“…(CFU/ml) was counted using similar procedures. Identification of Candida species was conducted according to the chromogenic properties of the medium 29 . In other words, different colours are shown by colonies of C. albicans (green), C. dubliniensis (dark green), C. tropicalis (dark blue, with a pink halo), and C. krusei (pink and downy appearance).…”

Heterogeneity in antifungal susceptibility of clones of Candida albicans isolated on single and sequential visits from a HIV‐infected southern Chinese cohort

“…The plates were incubated for 48 h at 37aeC, and up to 5 yeast colonies per sample were randomly chosen by a single investigator (YHS) and subcultured onto SDA plates. The pure yeast cultures were then harvested, suspended in water in sterile vials, and stored at ª20aeC until the organisms were identified by the germ tube test, API 20C AUX (Bio-Merieux, Marseilles, France) assimilation tests, boric acid resistance test, and the phenotype further defined using CHROMagar Candida plates (33).…”

Lectin typing of five medically important Candida species

“…23 Identification of Candida species by conventional morphology and assimilation tests can require 3-5 days or even longer for more difficult or unusual species. Although studies of colony morphology in solid medium remain important for the detection and presumptive identification of Candida yeasts, the inadequacy of such tests for accurate diagnosis has led to the use of other procedures, including differential medium tests, 24,25,26 chromogenic tests 27,28 and biochemical test kits. 29 Lectin agglutination tests constitute another approach for the identification and typing of yeasts, and are readily performed in the majority of laboratory contexts.…”