Comparative Evaluation of BD Phoenix and Vitek 2 Systems for Species Identification of Common and Uncommon Pathogenic Yeasts

Abstract

The BD Phoenix system was evaluated for species-level identification of yeasts (250 clinical isolates) and compared with the Vitek 2 system, using ribosomal internal transcribed spacer (ITS) sequence analysis as the gold standard. Considering only the species included in each system's database, 96.3% (236/245) and 91.4% (224/245) of the isolates were correctly identified by BD Phoenix and Vitek 2, respectively. During the last decades, the growing number of vulnerable hosts such as critically ill or otherwise immunocompromised patients-e.g., individuals with advanced HIV infection or cancer who are undergoing transplant-has resulted in ever-increasing diagnoses of fungal infections (1, 2), including those caused by unusual opportunistic yeasts (3). Together with Candida albicans, the species most frequently isolated from clinical specimens (4, 5), other yeast species are increasingly recovered from patients with well-documented infections (6-8). They encompass non-albicans Candida species, including the rarer species Candida famata, Candida kefyr, Candida lipolytica, Candida rugosa, and Candida utilis, as well as uncommon species belonging to the genera Trichosporon, Rhodotorula, Pichia, Malassezia, and Saccharomyces (3).It was recently observed that some yeast species are highly virulent and show reduced susceptibility to one or several antifungal agents (2,3,(8)(9)(10)(11)(12) and that this has important clinical repercussions, often resulting in therapeutic failures (6, 13-15). Thus, accurate identification of these species is of utmost importance (16), but this goal is difficult to achieve, at least using conventional phenotypic methods (17,18). In contrast, the newly developed matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) method may offer a highly discriminatory tool for identification of yeast isolates to the species level for C. albicans and Candida glabrata with unusual phenotypic or biochemical profiles as well (17), but to date its use has been curtailed or confined to large clinical microbiology laboratories (19).In this study, the performance of the BD Phoenix Yeast ID panel for use with the Phoenix system (Becton, Dickinson Diagnostics, Sparks, MD) was compared to that of the Vitek 2 colorimetric YST card for use with the Vitek 2 system (bioMérieux, Marcy l'Etoile, France) using a large collection of clinical isolates from common and less-common yeast species.(This work was presented in part at the 23rd European Congress of Clinical Microbiology and Infectious Diseases, Berlin, Germany, 27 to 30 April 2013.)A total of 250 selected isolates, representing 29 yeast species from seven genera (see Table S1 in the supplemental material), were routinely obtained from mycological cultures of clinical specimens (i.e., blood, cerebrospinal fluid, respiratory tract, stool, and urine) of individual patients hospitalized at the Università Cattolica del Sacro Cuore of Rome (Italy) during the calendar year 2012. Isolate identification was obtained as previously describ...

Misidentification of a Rare Species, Cryptococcus laurentii, by Commonly Used Commercial Biochemical Methods and Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry Systems: Challenges for Clinical Mycology Laboratories

“…It is widely recognized that commercial biochemical systems have limited accuracy in identifying rare yeast species (accuracy, 50 to 65%) (14)(15)(16). The present study further confirms these findings, as the Vitek 2 system was highly unreliable in the identification of C. laurentii.…”

Comparison of PhoenixTM Yeast ID Panel and API® ID 32C Commercial Systems for the Identification of Candida Species Isolated from Clinical Samples

“…Phoenix Yeast ID Panelin C.albicans'ı tanımlama oranı, API ID 32C'den biraz düşük (%92) olsa da aralarında anlamlı bir fark yoktur. Bu sistemin, Vitek 2 kolorimetrik YST kart ile karşılaştırıldığı benzer bir çalışmada, C.albicans suşları için %98 oranında uyumluluk saptanmıştır 18 . API ID 32C ile C.kefyr olarak tanımlanan ve morfolojik incelemeyle desteklenen altı izolat, Phoenix Yeast ID Panel tarafından S.cereviciae olarak tanımlanmıştır (Tablo I).…”

“…Ayrıca iki ticari tanımlama sistemi üretici firmaların önerileri doğrultusunda çalışıldı, sonuçların birbirleriyle uyumları karşılaştırıldı ve morfolojik bulguların tanımlamaya etkisi incelendi. Çalışmada değerlendirilen yöntemlerden biri, sadece asimilasyona dayanan ve birçok çalışmada kullanılmış güvenilir bir tanım-lama sistemi 14 olan API  ID 32C (bioMerieux, Fransa); diğeri ise asimilasyonun yanı sıra enzimatik reaksiyonları da kullanan, daha yeni ve deneyimin az olduğu tanımlama sistemi 18 Her iki sistemle farklı sonuç veren 27 izolatın tanımlanmasında, MT 80 agardaki morfolojik özellikleri yardımcı olmuş ve böylece toplam 186 (%88.1) izolat tür düze-yinde tanımlanmıştır. Morfolojik bulguların tanımlamaya eklenmesi, oranın %75.4'ten %88.1'e yükselmesini sağlamış; ancak bu artış istatistiksel olarak anlamlı bulunmamış-tır (p= 0.31).…”

Are the Conventional Commercial Yeast Identification Methods Still Helpful in the Era of New Clinical Microbiology Diagnostics? A Meta-Analysis of Their Accuracy

“…The main characteristics of the 26 studies (32-57), which were published between 1993 and 2014, are shown in Table 1 (see also Table S2 in the supplemental material). Among the 26 studies, 12 (32-34, 36-38, 40-43, 45, 54) reported on the identification performance of the AuxaColor system, 5 (35,38,39,43,54) reported on the identification performance of the API ID32C system, and 13 (44,(46)(47)(48)(49)(50)(51)(52)(53)(54)(55)(56)(57) reported on the identification performance of the Vitek 2 system operating with the ID-YST (fluorimetric) card (44,(46)(47)(48)(49) and/or the YST (colorimetric) card (47,48,(50)(51)(52)(53)(54)(55)(56)(57); among them, three were direct-comparison studies, of which two were between the AuxaColor and API ID32C systems (38,43) and one was among the AuxaColor, API ID32C, and Vitek 2 systems (54). Two studies evaluating the Vitek 2 system compared the colorimetric YST card with the older fluorimetric ID-YST card (47,48); however, we decided to include the results of these studies only with respect to the YST card.…”

“…In 3 of these studies (46,48,52), phenotypic methods were used in conjunction with molecular methods (i.e., sequencing of the internal transcribed spacer [ITS] region or the 18S-28S intersequence of ribosomal DNA [rDNA]) but only to resolve discrepant results between two phenotypic methods (i.e., the method under evaluation and that used as the reference method). Among the studies that employed molecular methods as reference methods (35,51,(53)(54)(55)(56), one study employed multilocus microsatellite-based PCR fingerprinting, and rDNA sequencing of all isolates was performed in the other 5 studies.…”