Identification of Candida species by restriction enzyme analysis

Background/aim: The identification of Candida species isolated from clinical specimens provides information about antifungal susceptibility and sheds light on the choice of empirical treatment. In the present study, restriction enzyme analysis of C. albicans and non-albicans Candida species previously identified by conventional methods was done to evaluate the utility of restriction enzyme analysis for more rapid and reliable identification of Candida species. Materials and methods: A total of 146 Candida strains isolated from various clinical specimens and ATCC strains were included. PCR products were digested with MwoI for all species and with BslI for C. parapsilosis and C. tropicalis strains. Results: The strains were identified by conventional methods as 40 C. albicans, 27 C. parapsilosis, 26 C. tropicalis, 25 C. glabrata, 11 C. kefyr, 10 C. krusei, and 7 C. guilliermondii strains. Restriction digestion with MwoI was able to distinguish between five different species (C. albicans, C. krusei, C. guilliermondii, C. kefyr, and C. glabrata), while BslI digestion could distinguish between C. tropicalis and C. parapsilosis. Conclusion: Restriction enzyme analysis with MwoI and BslI can be used for the identification of Candida species in situations where rapid identification is necessary or conventional methods are problematic.

Species level identification and antifungal susceptibility of yeasts isolated from various clinical specimens and evaluation of Integral System Yeasts Plus.

It is essential to use easy, standard, cost-effective and accurate methods for identification and susceptibility testing of yeasts in routine practice. This study aimed to establish the species distribution and antifungal susceptibility of yeast isolates and also to evaluate the performance of the colorimetric and commercially available Integral System Yeasts Plus (ISYP). Yeast isolates (n=116) were identified by conventional methods and ISYP. Antifungal susceptibility testing was performed by the microdilution method according to the standards of CLSI M27-A3 and ISYP. Candida albicans (50%) was the most common species isolated, followed by C. parapsilosis (25%) (mostly in blood samples). According to the CLSI M27-S3 criteria, resistance rates for amphotericin B, flucytosine, fluconazole, itraconazole, and voriconazole were 0%, 0%, 4.6%, 4.5% and 1.8%, respectively. Resistance for miconazole (MIC >1 mg/L) was found as 17.9%. Sixty-two (53.4%) of the isolates which were analyzed by ISYP showed disagreement with those identified by the conventional methods and API ID 32C identification kit or a specific identification code could not be assigned by ISYP. The performance of ISYP could be indicated as low for all antifungal drugs tested according to the ROC analysis (AUC: 0.28-0.56). As the current version of ISYP displays a poor performance, it is recommended to use the other commercial systems whose results are approved as reliable and in agreement with those of the reference methods in identification and susceptibility testing of yeasts.