C-212. Multi-center Evaluation of BBL ™ CHROMagar™ Candida Medium for the Detection and Identification of Yeast from Vaginal Specimens

J. L. Cromien1, R. L. Kaplan2, D. A. Schwab3, R. F. Cammarata4, P. L. Cerwinka5, C. L. Wong6, L. M. Zuchowski7, D. S. Mincarelli8;
1Quest Diagnostics, St. Louis, MO, 2Quest Diagnostics, Atlanta, GA, 3Quest Diagnostics, San Juan Capistrano, CA, 4Quest Diagnostics, Syosset, NY, 5Quest Diagnostics, Collegeville, PA, 6Quest Diagnostics, Wallingford, CT, 7Quest Diagnostics, Lenexa, KS, 8Quest Diagnostics, Horsham, PA.

BBL ™ CHROMagar™ Candida Medium (CAC) is a prepared selective medium for the isolation of yeast and filamentous fungi that also allows for the differentiation of Candida albicans, C. tropicalis, and C. krusei. We evaluated the performance of this medium in two Quest Diagnostics microbiology laboratories for isolation and characterization of yeast commonly encountered from vaginal specimens. Testing included a total of 204 strains, representing 12 different species of yeast. All 105 isolates of C. albicans grew on the CAC medium demonstrating distinctive green colonies. No other isolates demonstrated similar appearance. All 20 isolates of C. tropicalis grew on CAC demonstrating dark blue colonies. One isolate of C. ciferrii also demonstrated a blue colony, but growth was dry and wrinkled in appearance, as opposed to the creamy appearance of the C. tropicalis. All 21 isolates of C. krusei grew on CAC yielding rough colonies with pink to mauve centers and white borders. A single isolate of B. capitatus demonstrated similar morphology and would have been misidentified as C. krusei based solely on the appearance on CAC. All 25 isolates of C. glabrata tested would have been correctly classified as yeast, not consistent with C. albicans, C. tropicalis, or C. krusei. The addition of a Rapid Trehalose Test, performed on these isolates directly from the CAC, correctly classified these strains as C. glabrata. Parallel plating of 668 vaginal specimens onto CAC in addition to the routine culture media yielded a total of 104 cultures positive for yeast. 103 (99%) of these yeast isolates were recovered on primary CAC, while 95 (91%) were recovered by initial standard culture. Identification of isolates based on CAC allowed for results to be reported 48 hours sooner than with standard culture methods. Based on this evaluation it appears that CAC provides a useful, rapid determination of the most common Candida species recovered from vaginal swabs.