DIFFERENTIAL AND ENRICHMENT MEDIA FOR SELECTIVE CULTURE AND RECOGNITION OF YEAST SPECIES FROM CLINICAL MATERIAL

An enrichment medium was developed and evaluated for isolation of fluconazole-resistant minority yeast species in a hospital setting. The enrichment medium was made by adding fluconazole (10 mu g/ml) to yeast nitrogen base/glucose broth. Under laboratory conditions the broth permitted detection of 20 of 20 Candida krusei isolates and 20 of 20 Candida glabrata isolates in mixtures with Candida albicans even when the Candida albicans cells outnumbered those of the other species by 1000:1. Results of culture on the enrichment medium were compared with those obtained on routine agar media and on a yeast differential agar which facilitates detection of mixed yeast species by their colony colours. Only one Candida glabrata isolate was detected on the enrichment broth but not found on routine culture of 68 yeast-positive clinical specimens. However, bacterial overgrowth in some broths may have retarded the appearance of other yeast isolates. On the yeast differential agar, 20 clinical specimens were found to contain mixtures of yeast species compared with only 2 on routine culture.