Comparative evaluation of the Bruker Biotyper and Vitek MS matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) systems for non-albicans Candida and uncommon yeast isolates.

Rapid and accurate diagnosis is critically important in invasive and disseminated fungal infections for appropriate antifungal treatment. MALDI-TOF MS systems are effective for fast and accurate identification of Candida species. We aimed to compare two MALDI-TOF MS systems for the rapid identification of non-albicans Candida and rare clinical yeast species. This study included 157 isolates representing 23 yeast species. All isolates were identified using Bruker MALDI Biotyper and VITEK MS systems. If both MALDI-TOF MS systems yielded the same results for a certain isolate, the identification is regarded as correct. We performed internal transcribed spacer (ITS) DNA sequencing on five fungal isolates with discordant species names or that were unidentified by the two MALDI-TOF MS systems. The yeast identification sensitivity of MALDI Biotyper was 98.7%, whereas that of VITEK MS was 96.8%. Both MALDI-TOF MS systems correctly identified all strains belonging to four prevalent species, namely, Candida parapsilosis, Candida tropicalis, Candida glabrata, and Candida krusei. For the 19 rare clinical yeast species, identification rates were 96.7% for MALDI Biotyper and 91.7% for VITEK MS. The ITS sequence analysis of five isolates yielded two Meyerozyma caribbica, two Cyberlindnera fabianii, and one Candida dubliniensis. This study showed the high performance of both MALDI-TOF MS systems, identifying over 90% of yeast isolates in a short time. The disadvantages of these systems are that some species are not present in the databases and it cannot distinguish closely related species. The sensitivity of MALDI-TOF MS systems constantly improves with the expansion of databases in parallel with taxonomic developments for the identification of rare clinical yeast species.

Teke L ，Barış A ，Bayraktar B 《-》

Comparison of the Bruker Biotyper and VITEK MS Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry Systems Using a Formic Acid Extraction Method to Identify Common and Uncommon Yeast Isolates.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) allows rapid and accurate identification of clinical yeast isolates. In-tube formic acid/acetonitrile (FA/ACN) extraction is recommended prior to the analysis with MALDI Biotyper, but the direct on-plate FA extraction is simpler. We compared the Biotyper with the VITEK MS for the identification of various clinically relevant yeast species, focusing on the use of the FA extraction method. We analyzed 309 clinical isolates of 42 yeast species (four common Candida species, Cryptococcus neoformans, and 37 uncommon yeast species) using the Biotyper and VITEK MS systems. FA extraction was used initially for all isolates. If 'no identification' result was obtained following the initial FA extraction, these samples were then retested by using FA (both systems, additive FA) or FA/ACN (Biotyper only, additive FA/ACN) extraction. These results were compared with those obtained by sequence-based identification. Both systems correctly identified all 158 isolates of the four common Candida species after the initial FA extraction. The Biotyper correctly identified 8.7%, 30.4%, and 100% of 23 C. neoformans isolates after performing initial FA, additive FA, and FA/ACN extractions, respectively, while VITEK MS identified all C. neoformans isolates after the initial FA extraction. Both systems had comparable identification rates of 37 uncommon yeast species (128 isolates), following the initial FA (Biotyper, 74.2%; VITEK MS, 73.4%) or additive FA (Biotyper, 82.0%; VITEK MS, 73.4%). The identification rate of most common and uncommon yeast isolates is comparable between simple FA extraction/Biotyper method and VITEK MS methods, but FA/ACN extraction is necessary for C. neoformans identification by Biotyper.

Lee HS ，Shin JH ，Choi MJ ，Won EJ ，Kee SJ ，Kim SH ，Shin MG ，Suh SP ... -  《-》

Comparative evaluation of two matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) systems for the identification of clinically significant yeasts.

To prospectively evaluate the performance of two matrix-assisted laser desorption/ionization time-of-flight mass spectrometry systems (MALDI-TOF MS) for the identification of clinically significant yeast isolates compared to the VITEK 2 system. One hundred and eighty-eight consecutive yeast isolates were analyzed by Bruker Biotyper and VITEK MS. The results were compared with the conventional VITEK 2 yeast identification system. Discrepant results were resolved by direct sequencing of rDNA. Accurate identification by VITEK 2, VITEK MS, and Bruker Biotyper MS was 94.1% (177/188), 93.0% (175/188), and 92.6% (174/188), respectively. Three isolates were not identified by VITEK MS, while nine Candida orthopsilosis were misidentified as Candida parapsilosis, as this species is not present in its database. Eleven isolates were not identified or were wrongly identified by Bruker Biotyper and although another 14 were correctly identified, the score was unreliable at <1.7. The overall accuracy of rapid MALDI-TOF MS systems was essentially comparable to that of the conventional VITEK 2 yeast identification system. However, future expansion of the databases may further improve the outcome and accuracy of identification of yeast species.

Jamal WY ，Ahmad S ，Khan ZU ，Rotimi VO ... -  《-》

Comparison of the accuracy of two conventional phenotypic methods and two MALDI-TOF MS systems with that of DNA sequencing analysis for correctly identifying clinically encountered yeasts.

Chao QT ，Lee TF ，Teng SH ，Peng LY ，Chen PH ，Teng LJ ，Hsueh PR ... -  《PLoS One》

Species identification and antifungal susceptibility of uncommon blood yeast isolates.

Accurate identification of Candida species is increasingly important in the era of emergence of Candida auris. We aimed to compare the identification performance of two matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) systems (Vitek MS and Bruker biotyper MS) and an oligonucleotide array for uncommon blood yeast isolates and demonstrate the susceptibilities among those isolates. Candida species isolates from blood culture other than Candida albicans, Candida parapsilosis, Candida tropicalis, Candida glabrata, and Candida krusei identified by biochemical methods were collected from multiple hospitals and further identified by an oligonucleotide array based on the internal transcribed spacer-1 (ITS-1) and ITS-2 sequences of the rRNA genes, Vitek MS and Bruker biotyper MS. The minimal inhibitory concentrations (MICs) of these clinical isolates were determined by the Sensititre YeastOne (SYO) system. Among 136 isolates, Candida guilliermondii was most common (52, 38.2%), followed by C. lusitaniae (13, 9.6%) and C. haemulonii (12, 8.8%). The oligonucleotide array, Vitek MS and Bruker biotyper MS correctly identified 89.7% (122), 90.4% (123), and 92.6% (126) of these isolates, respectively. Elevated minimal inhibitory concentrations (MICs) of fluconazole were observed for C. haemulonii (MIC90: 256 mg/L), and C. guilliermondii (MIC90: 16 mg/L) with 28.4% of uncommon Candida isolates with MIC ≧ 8 mg/L. For uncommon Candida species, the unmet need for current databases of two commercial MALDI-TOF MS systems is highlighted, and the oligonucleotide array may serve as a supplement.

Li MC ，Tang HJ ，Wu CJ ，Wang SW ，Su SL ，Liu WL ，Ko WC ，Chen YC ... -  《-》