Candida albicans identification: comparison among nine phenotypic systems and a multiplex PCR.

BACKGROUND

Candida albicans is the most common fungal pathogen isolated from clinical samples and is also the most common yeast species carried as a commensal by healthy individuals although some non-C. albicans species account for an important number of infections.

OBJECTIVES

To compare nine phenotypic systems for C. albicans identification [API 20C AUX; RapID Yeast Identification panel (RYIP); Vitek2 ID-YST system; chromogenic media, CHRO-Magar, Oxoid Chromogenic Candida Agar (OCCA), Candida ID2, Candida Identification Agar, CandiSelect 4, and Chromalbicans Agar] with multiplex PCR.

PATIENTS/METHODS: A collection of 390 yeast strains was obtained by routine isolation from oral and vaginal swabs. All of the yeasts isolated were tested for germ tube formation, and then submitted to a multiplex PCR protocol tested in previous studies, and to nine phenotypical commercial methods, together with the reference ATCC strains. Comparison was limited to the ability of the tests to identify C. albicans.

RESULTS

253 isolates were provisionally identified as C. albicans by germ tube, and their identities were further confirmed with the multiplex PCR. Sensitivity of phenotypical systems ranged from 81.9% (Vitek2) to 87.7% (Candida ID2 e CHROMagar). For specificity, the highest value was 96.8% for Candida ID2, and the lowest value (75.1%) was for Chromalbicans Agar.

CONCLUSIONS

Although with differences in discriminatory power, the methods tested showed overall acceptable levels of sensitivity and specificity respect to the multiplex PCR; therefore, all could be useful for C. albicans identification where molecular differentiation is not available.