The Sensititre Yeast One method (AccuMed International Ltd, East Grinstead, UK) is a microplate-based procedure that incorporates an oxidation-reduction indicator, Alamar Blue, for the in-vitro testing of five antifungal agents (amphotericin B, fluconazole, itraconazole, ketoconazole and flucytosine). We compared this colorimetric method with a standard broth microdilution test, performed according to US National Committee for Clinical Laboratory Standards document M27-A guidelines, for determining the in-vitro susceptibilities of 180 isolates of Candida spp. (50 Candida albicans, 50 Candida glabrata, ten Candida kefyr, 20 Candida krusei, ten Candida lusitaniae, 20 Candida parapsilosis and 20 Candida tropicalis) and 20 isolates of Cryptococcus neoformans. The overall agreement between the results of the two methods (colorimetric MICs within +/- two log2 dilutions of standard MICs) were 99% for amphotericin B, 96.5% for flucytosine, 93% for itraconazole, 91.5% for fluconazole and 85.5% for ketoconazole. The overall levels of agreement between the two methods were > or = 94% for six of the eight species tested, the exceptions being C. neoformans and C. tropicalis where the overall agreement was 89% and 80% respectively. The poorest agreement between the results for individual agents was seen with C. tropicalis and the three azole agents (60-75% of colorimetric MICs within +/- two log2 dilutions of standard MICs), and C. neoformans for ketoconazole (50%). The Yeast One method appears to be a suitable alternative procedure for routine antifungal susceptibility testing of Candida spp. and C. neoformans.

The in-vitro susceptibilities of 143 isolates of Cryptococcus neoformans, collected from British patients between 1994 and 1996, to fluconazole and itraconazole were compared with those of 36 isolates collected between 1971 and 1985, 41 isolates collected between 1986 and 1989, and 43 Ugandan isolates collected in 1996. Testing was done with a broth microdilution method in YNB medium supplemented with glucose, incubation at 30 degrees C for 72 h, and an endpoint of 50% inhibition. The results showed that the MIC ranges, MIC50s and MIC90s of fluconazole and itraconazole for C. neoformans isolates from the UK have remained unchanged despite the recent widespread use of triazoles for long-term maintenance of patients with AIDS-associated cryptococcal meningitis. The MIC ranges, MIC50s and MIC90s of the 43 isolates from untreated Ugandan patients with AIDS were similar to those of the British isolates. Examination of our records for 1994-96 revealed six cases in which a four-fold or greater rise in the MIC of fluconazole was associated with relapsed cryptococcal meningitis.

No abstract

The FUNGITEST method (Sanofi Diagnostics Pasteur, Paris, France) is a microplate-based procedure for the breakpoint testing of six antifungal agents (amphotericin B, flucytosine, fluconazole, itraconazole, ketoconazole, and miconazole). We compared the FUNGITEST method with a broth microdilution test, performed according to National Committee for Clinical Laboratory Standards document M27-A guidelines, for determining the in vitro susceptibilities of 180 isolates ofCandida spp. (50 C. albicans, 50C. glabrata, 10 C. kefyr, 20C. krusei, 10 C. lusitaniae, 20C. parapsilosis, and 20 C. tropicalisisolates) and 20 isolates of Cryptococcus neoformans. Overall, there was 100% agreement between the methods for amphotericin B, 95% agreement for flucytosine, 84% agreement for miconazole, 83% agreement for itraconazole, 77% agreement for ketoconazole, and 76% agreement for fluconazole. The overall agreement between the methods exceeded 80% for all species tested with the exception ofC. glabrata (71% agreement). The poorest agreement between the results for individual agents was seen with C. glabrata (38% for fluconazole, 44% for ketoconazole, and 56% for itraconazole) and C. tropicalis (50% for miconazole). The FUNGITEST method misclassified as susceptible 2 of 12 (16.6%) fluconazole-resistant isolates, 2 of 10 (20%) itraconazole-resistant isolates, and 4 of 8 (50%) ketoconazole-resistant isolates of several Candida spp. Further development of the FUNGITEST procedure will be required before it can be recommended as an alternative method for the susceptibility testing of Candida spp. or C. neoformans.

Two commercial systems for the identification of yeasts were evaluated by using 159 clinical isolates that had also been identified by conventional biochemical and morphological methods. The API Candida system correctly identified 146 isolates (91.8%), and the AUXACOLOR system correctly identified 145 isolates (91.2%). However, of the 146 isolates identified by the API Candida system, 23 required supplemental biochemical tests or morphological assessment to obtain the correct identification. The AUXACOLOR system gave no identification in 13 cases (8.2%), while the API Candida system gave an unreadable profile in only one case. Incorrect identifications were more common with the API Candida system (12 isolates; 7.5%) than with the AUXACOLOR system (1 isolate; 0.6%).