Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 6/5/2008
Publication Date: 6/5/2008
Citation: Bishop, J.A., Chase, N., Lee, R., Kurtzman, C.P., Merz, W.G. 2008. Production of white colonies on CHROMagar Candida BD by species in the C. glabrata clade, and other species with overlapping phenotypic traits.. Meeting Abstract. Interpretive Summary:
Technical Abstract: Chromogenic agars are important diagnostic media used in the clinical mycology laboratory. Candida spp. that produced white colonies on CHROMagar Candida (Becton Dickinson) (CAC) were found during a study designed to detect and identify C. bracarensis, a newly-described species in the C. glabrata clade. White colonies have also been noted among other members of this clade and other species that are often difficult to identify due to relatively few positive biochemical reactions and overlapping phenotypic traits. Hence, the hypothesis tested was that other species of this clade and species with similar phenotypic traits would also produce white colonies. A total of 134 yeast isolates were tested included 2 C. bracarensis controls, 122 recent C. glabrata clinical isolates (identified by phenotypic assays) and 10 reference strains representing 6 other Candida species. Isolates were coded, inoculated onto CAC plates, incubated at 25, 30, and 37° C. The plates were read independently by 2 individuals for color at 24 and 48 hr. Isolates that produced white colonies at 2 or 3 temperatures were considered positive, and identifications were confirmed by LSU D1/D2 sequencing and API 20C testing (BioMerieux). Overall, 16/134 isolates produced white colonies. They included 2/2 C. bracarensis control strains, 11/122 recent C. glabrata clinical isolates (molecularly identified as 3 C. bracarensis, 1 C. norvegenesis and 7 C .glabrata) and 3/10 reference strains (0/4 C. norvegenesis, 2/2 C. inconspicua, 1/1 C. nivariensis, 0/1 C. lambica, 0/1 C. monosa, and 0/1 Pichia fermentens. White colony color was associated with temperature; more positives were seen at 25 deg C than at 30 or 37 deg C. Excluding glucose, only 1-2 of the 18 carbohydrates (glycerol and/or trehalose) in the API 20C were assimilated by the 5 Candida species that produced white colonies. These data support our hypothesis: white colonies were produced by 5/8 species tested which included 4/6 selected or related species. Clinical laboratories should be aware that yeast that produce white colonies on CAC may be difficult to identify phenotypically and may ultimately require molecular assays.