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

Formic acid sandwich method is well-suited for filamentous fungi identification and improves turn around time using Zybio EXS2600 mass spectrometry

OBJECTIVES

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is extensively employed for the identification of filamentous fungi on MALDI Biotyper (Bruker Daltonics) and Vitek MS (biomerieux), but the performance of fungi identification on new EXS2600 (Zybio) is still unknow. Our study aims to evaluate the new EXS2600 system's (Zybio) ability to rapidly identify filamentous fungi and determine its effect on turnaround time (TAT) in our laboratory.

METHODS

We tested 117 filamentous fungi using two pretreatment methods: the formic acid sandwich (FA-sandwich) and a commercial mold extraction kit (MEK, Zybio). All isolates were confirmed via sequence analysis. Laboratory data were extracted from our laboratory information system over two 9-month periods: pre-EXS (April to December 2022) and post-EXS (April to December 2023), respectively.

RESULTS

The total correct identification (at the species, genus, or complex/group level) rate of fungi was high, FA-sandwich (95.73%, 112/117), followed by MEK (94.02%, 110/117). Excluding 6 isolates not in the database, species-level identification accuracy was 92.79% (103/111) for FA-sandwich and 91.89% (102/111) for MEK; genus-level accuracy was 97.29% (108/111) and 96.39% (107/111), respectively. Both methods attained a 100% correct identification rate for Aspergillus, Lichtheimia, Rhizopus Mucor and Talaromyces species, and were able to differentiate between Fusarium verticillioides and Fusarium proliferatum within the Fusarium fujikuroi species complex. Notably, high confidence was observed in the species-level identification of uncommon fungi such as Trichothecium roseum and Geotrichum candidum. The TAT for all positive cultures decreased from pre EXS2600 to post (108.379 VS 102.438, P < 0.05), and the TAT for tissue decreased most (451.538 VS 222.304, P < 0.001).

CONCLUSIONS

The FA-sandwich method is more efficient and accurate for identifying filamentous fungi with EXS2600 than the MEK. Our study firstly evaluated the performance of fungi identification on EXS2600 and showed it is suitable for clinical microbiology laboratories use.

MALDI-TOF MS: A Reliable Tool in the Real Life of the Clinical Microbiology Laboratory

Matrix-Assisted Desorption/Ionization-Time of Flight Mass Spectrometry (MALDI-TOF MS) in the last decade has revealed itself as a valid support in the workflow in the clinical microbiology laboratory for the identification of bacteria and fungi, demonstrating high reliability and effectiveness in this application. Its use has reduced, by 24 h, the time to obtain a microbiological diagnosis compared to conventional biochemical automatic systems. MALDI-TOF MS application to the detection of pathogens directly in clinical samples was proposed but requires a deeper investigation, whereas its application to positive blood cultures for the identification of microorganisms and the detection of antimicrobial resistance are now the most useful applications. Thanks to its rapidity, accuracy, and low price in reagents and consumables, MALDI-TOF MS has also been applied to different fields of clinical microbiology, such as the detection of antibiotic susceptibility/resistance biomarkers, the identification of aminoacidic sequences and the chemical structure of protein terminal groups, and as an emerging method in microbial typing. Some of these applications are waiting for an extensive evaluation before confirming a transfer to the routine. MALDI-TOF MS has not yet been used for the routine identification of parasites; nevertheless, studies have been reported in the last few years on its use in the identification of intestinal protozoa, Plasmodium falciparum, or ectoparasites. Innovative applications of MALDI-TOF MS to viruses' identification were also reported, seeking further studies before adapting this tool to the virus's diagnostic. This mini-review is focused on the MALDI-TOF MS application in the real life of the diagnostic microbiology laboratory.

Nationwide Surveillance of Antifungal Resistance of Candida Bloodstream Isolates in South Korean Hospitals: Two Year Report from Kor-GLASS

We incorporated nationwide Candida antifungal surveillance into the Korea Global Antimicrobial Resistance Surveillance System (Kor-GLASS) for bacterial pathogens. We prospectively collected and analyzed complete non-duplicate blood isolates and information from nine sentinel hospitals during 2020−2021, based on GLASS early implementation protocol for the inclusion of Candida species. Candida species ranked fourth among 10,758 target blood pathogens and second among 4050 hospital-origin blood pathogens. Among 766 Candida blood isolates, 87.6% were of hospital origin, and 41.3% occurred in intensive care unit patients. Adults > 60 years of age accounted for 75.7% of cases. Based on species-specific clinical breakpoints, non-susceptibility to fluconazole, voriconazole, caspofungin, micafungin, and anidulafungin was found in 21.1% (154/729), 4.0% (24/596), 0.1% (1/741), 0.0% (0/741), and 0.1% (1/741) of the isolates, respectively. Fluconazole resistance was determined in 0% (0/348), 2.2% (3/135, 1 Erg11 mutant), 5.3% (7/133, 6 Pdr1 mutants), and 5.6% (6/108, 4 Erg11 and 1 Cdr1 mutants) of C. albicans, C. tropicalis, C. glabrata, and C. parapsilosis isolates, respectively. An echinocandin-resistant C. glabrata isolate harbored an F659Y mutation in Fks2p. The inclusion of Candida species in the Kor-GLASS system generated well-curated surveillance data and may encourage global Candida surveillance efforts using a harmonized GLASS system.

“Omic” Approaches to Bacteria and Antibiotic Resistance Identification

The quick and accurate identification of microorganisms and the study of resistance to antibiotics is crucial in the economic and industrial fields along with medicine. One of the fastest-growing identification methods is the spectrometric approach consisting in the matrix-assisted laser ionization/desorption using a time-of-flight analyzer (MALDI-TOF MS), which has many advantages over conventional methods for the determination of microorganisms presented. Thanks to the use of a multiomic approach in the MALDI-TOF MS analysis, it is possible to obtain a broad spectrum of data allowing the identification of microorganisms, understanding their interactions and the analysis of antibiotic resistance mechanisms. In addition, the literature data indicate the possibility of a significant reduction in the time of the sample preparation and analysis time, which will enable a faster initiation of the treatment of patients. However, it is still necessary to improve the process of identifying and supplementing the existing databases along with creating new ones. This review summarizes the use of “-omics” approaches in the MALDI TOF MS analysis, including in bacterial identification and antibiotic resistance mechanisms analysis.

Candida dubliniensis fungemia in a patient with severe COVID-19: A case report

Candida dubliniensis phenotypically mimics Candida albicans in its microbiological features; thus, its clinical characteristics have yet to be fully elucidated. Here we report the case of a 68-year-old Japanese man who developed C. dubliniensis fungemia during treatment for severe coronavirus disease 2019 (COVID-19). The patient was intubated and received a combination of immunosuppressants, including high-dose methylprednisolone and two doses of tocilizumab, as well as remdesivir, intravenous heparin, and ceftriaxone. A blood culture on admission day 11 revealed Candida species, which was confirmed as C. dubliniensis by mass spectrometry. An additional sequencing analysis of the 26S rDNA and ITS regions confirmed that the organism was 100% identical to the reference strain of C. dubliniensis (ATCC MYA-646). Considering the simultaneous isolation of C. dubliniensis from a sputum sample, the lower respiratory tract could be an entry point for candidemia. Although treatment with micafungin successfully eradicated the C. dubliniensis fungemia, the patient died of COVID-19 progression. In this case, aggressive immunosuppressive therapy could have caused the C. dubliniensis fungemia. Due to insufficient clinical reports on C. dubliniensis infection based on definitive diagnosis, the whole picture of the cryptic organism is still unknown. Further accumulation of clinical and microbiological data of the pathogen is needed to elucidate their clinical significance.

Evaluation of Serotyping of Environmental and Clinical Isolates of Legionella pneumophila using MALDI-TOF MS

Legionella pneumophila (L. pneumophila) is responsible for most Legionnaire's disease cases diagnosed worldwide. The species includes 16 serogroups, but most Legionnaire's disease cases (85.7% in Europe, 87.0% in Japan) are caused by L. pneumophila serogroup 1. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) can be used to identify the L. pneumophila serogroup. In this study, we compared three sample preparation methods that are compatible with MALDI-TOF MS: the direct colony transfer method (DCTM), on-target extraction method (OTEM), and in-tube extraction method (ITEM). The aim was to improve the low identification rates for L. pneumophila, and establish and validate a simple, rapid and robust MALDI-TOF MS-based method for routine use in microbiological laboratories for assignment of L. pneumophila isolates to serogroups and identification of reliable peak biomarkers. Using ITEM, 100.0% (29/29) of hot spring water samples and clinical isolates were correctly identified at the species level. Augmented reference spectra correctly identified all 29 strains at the species level and 29 isolates at the serogroup level, displaying sensitivity, specificity and accuracy of 100.0% for serogroup assignment. MALDI-TOF MS is a relatively inexpensive method for assignment of L. pneumophila serogroups that can serve as a first-line tool for rapid prospective typing.

Mass spectrometry in research laboratories and clinical diagnostic: a new era in medical mycology

Diagnosis by clinical mycology laboratory plays a critical role in patient care by providing definitive knowledge of the cause of infection and antimicrobial susceptibility data to physicians. Rapid diagnostic methods are likely to improve patient. Aggressive resuscitation bundles, adequate source control, and appropriate antibiotic therapy are cornerstones for success in the treatment of patients. Routine methods for identifying clinical specimen fungal pathogen are based on the cultivation on different media with the subsequent examination of its phenotypic characteristics comprising a combination of microscopic and colony morphologies. As some fungi cannot be readily identified using these methods, molecular diagnostic methods may be required. These methods are fast, but it can cost a lot. Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) is suitable for high-throughput and rapid diagnostics at low costs. It can be considered an alternative for conventional biochemical and molecular identification systems in a microbiological laboratory. The reliability and accuracy of this method have been scrutinized in many surveys and have been compared with several methods including sequencing and molecular methods. According to these findings, the reliability and accuracy of this method are very high and can be trusted. With all the benefits of this technique, the libraries of MALDI-TOF MS need to be strengthened to enhance its performance. This review provides an overview of the most recent research literature that has investigated the applications and usage of MT-MS to the identification of microorganisms, mycotoxins, antifungal susceptibility examination, and mycobiome research.

Identification of Peptoniphilus harei From Blood Cultures in an Infected Aortic Aneurysm Patient: Case Report and Review Published Literature

Gram-positive anaerobic cocci (GPAC) are a commensal part of human flora but are also opportunistic pathogens. This is possibly the first study to report a case of Peptoniphilus harei bacteremia in an abdominal aortic aneurysm (AAA) patient. Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) failed to identify the isolate and molecular analysis confirmed it as P. harei. A comprehensive literature review revealed that P. harei is an emergent pathogen. This study serves as a reminder for practicing clinicians to include anaerobic blood cultures as part of their blood culture procedures; this is particularly important situations with a high level of suspicion of infection factors in some noninfectious diseases, as mentioned in this publication. Clinical microbiologists should be aware that the pathogenic potential of GPAC can be greatly underestimated leading to incorrect diagnosis on using only one method for pathogen identification. Upgradation and correction of the MALDI-TOF MS databases is recommended to provide reliable and rapid identification of GPAC at species level in medical diagnostic microbiology laboratories.

Re-classification of Streptomyces venezuelae strains and mining secondary metabolite biosynthetic gene clusters

Streptomyces species have attracted considerable interest as a reservoir of medically important secondary metabolites, which are even diverse and different between strains. Here, we reassess ten Streptomyces venezuelae strains by presenting the highly resolved classification, using 16S rRNA sequencing, MALDI-TOF MS protein profiling, and whole-genome sequencing. The results revealed that seven of the ten strains were misclassified as S. venezuelae species. Secondary metabolite biosynthetic gene cluster (smBGC) mining and targeted LC-MS/MS based metabolite screening of S. venezuelae and misclassified strains identified in total 59 secondary metabolites production. In addition, a comparison of pyrrolamide-type antibiotic BGCs of four misclassified strains, followed by functional genomics, revealed that athv28 is critical in the synthesis of the anthelvencin precursor, 5-amino-3,4-dihydro-2H-pyrrole-2-carboxylate (ADPC). Our findings illustrate the importance of the accurate classification and better utilization of misclassified Streptomyces strains to discover smBGCs and their secondary metabolite products.

Disk Diffusion Susceptibility Testing for the Rapid Detection of Fluconazole Resistance in Candida Isolates

Background

Given the increased fluconazole resistance (FR) among Candida isolates, we assessed the suitability of disk diffusion susceptibility testing (DDT) for the early detection of FR using well-characterized Candida isolates.

Methods

In total, 188 Candida isolates, including 66 C. albicans (seven Erg11 mutants), 69 C. glabrata (33 Pdr1 mutants), 29 C. parapsilosis (15 Erg11 mutants), and 24 C. tropicalis (eight Erg11 mutants) isolates, were tested in this study. FR was assessed using DDT according to the standard CLSI M44-ED3 method, except that two cell suspensions, McFarland 0.5 (standard inoculum) and 2.5 (large inoculum), were used, and the inhibition zones were read at 2-hour intervals from 10 hours to 24 hours.

Results

DDT results for the standard inoculum were readable after 14 hours (C. albicans, C. glabrata, and C. tropicalis) and 20 hours (C. parapsilosis) for >95% of the isolates, whereas the results for the large inoculum were readable after 12 hours (C. glabrata and C. tropicalis), 14 hours (C. albicans), and 16 hours (C. parapsilosis) for >95% of the isolates. Compared with the results produced using the CLSI M27-ED4 broth microdilution method, the first readable results from the DDT method for each isolate exhibited an agreement of 97.0%, 98.6%, 72.4%, and 91.7% for the standard inoculum and 100%, 98.6%, 96.6%, and 95.8% for the large inoculum for C. albicans, C. glabrata, C. parapsilosis, and C. tropicalis, respectively.

Conclusions

DDT using large inoculum may detect FR rapidly and reliably in the four most common Candida species.

MASS SPECTROMETRY TECHNOLOGIES TO ADVANCE CARE FOR CANCER PATIENTS IN CLINICAL AND INTRAOPERATIVE USE

Developments in mass spectrometry technologies have driven a widespread interest and expanded their use in cancer-related research and clinical applications. In this review, we highlight the developments in mass spectrometry methods and instrumentation applied to direct tissue analysis that have been tailored at enhancing performance in clinical research as well as facilitating translation and implementation of mass spectrometry in clinical settings, with a focus on cancer-related studies. Notable studies demonstrating the capabilities of direct mass spectrometry analysis in biomarker discovery, cancer diagnosis and prognosis, tissue analysis during oncologic surgeries, and other clinically relevant problems that have the potential to substantially advance cancer patient care are discussed. Key challenges that need to be addressed before routine clinical implementation including regulatory efforts are also discussed. Overall, the studies highlighted in this review demonstrate the transformative potential of mass spectrometry technologies to advance clinical research and care for cancer patients. © 2020 Wiley Periodicals, Inc. Mass Spec Rev.

MALDI-TOF Mass Spectrometry and 16S rRNA Gene Sequence Analysis for the Identification of Foodborne Clostridium Spp

BACKGROUND

Clostridium is a genus of Gram-positive, spore-forming, anaerobic bacteria comprising approximately 100 species. Some Clostridium spp. (C. botulinum, C. perfringens, C. tetani and C. difficile) were recognized to cause acute food poisoning, botulism, tetanus, and diarrheal illness in humans. Thus, rapid identification of Clostridium spp. is critical for source tracking of contaminated food and to understand the transmission dynamics of these foodborne pathogens.

OBJECTIVE

This study was carried out to rapidly identify Clostridium-like isolates by MALDI-TOF MS and rRNA sequencing methods.

METHODS

Thirty-three Clostridium-like isolates were recovered from various baby food and surveillance samples. Species identification of these isolates was accomplished using VITEK MS system. Sequence characterization of the 16S rRNA region was done on an ABI 3500XL Genetic Analyzer.

RESULTS

The VITEK MS system identified 28 of the 33 Clostridium-like isolates with a high confidence value (99.9%); no ID was observed for the rest of the five isolates. Nucleotide sequencing of 16S rRNA region identified all 33 Clostridium-like isolates. Furthermore, while characterizing the 16S rRNA gene, eleven distinct Clostridium spp. (Clostridium aciditolerans, Clostridium aerotolerans, Clostridium argentinense, Clostridium beijerinckii, Clostridium bifermentans, Clostridium butyricum, Clostridium cochlearium, Clostridium difficile, Clostridium perfringens, Clostridium sporogenes, and Clostridium subterminale) were recognized among the 33 Clostridium-like isolates. One of the Clostridium-like isolate was identified as the Citrobacter amalonaticus by both diagnostic methods. The generated 16S rRNA sequences matched completely (100%) with sequences available in GenBank for Clostridium and Citrobacter species. Species identification attained by the VITEK MS for the Clostridium-like isolates was comparable to the 16S rRNA sequencing based data.

HIGHLIGHTS

MALDI-TOF mass spectrometry and 16S rRNA sequencing can be used in the species identification of Clostridium species.

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

INTRODUCTION

Rapid and accurate diagnosis is critically important in invasive and disseminated fungal infections for appropriate antifungal treatment.

HYPOTHESIS

MALDI-TOF MS systems are effective for fast and accurate identification of Candida species.

AIM

We aimed to compare two MALDI-TOF MS systems for the rapid identification of non-albicans Candida and rare clinical yeast species.

METHODOLOGY

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.

RESULTS

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.

CONCLUSIONS

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.

Matrix-Assisted Laser Desorption Ionization Time-of-Flight for Fungal Identification

Many studies have shown successful performance of matrix-assisted laser desorption ionization time-of-flight mass spectrometry for rapid yeast and mold identification, yet few laboratories have chosen to apply this technology into their routine clinical mycology workflow. This review provides an overview of the current status of matrix-assisted laser desorption ionization time-of-flight mass spectrometry for fungal identification, including key findings in the literature, processing and database considerations, updates in technology, and exciting future prospects. Significant advances toward standardization have taken place recently; thus, accurate species-level identification of yeasts and molds should be highly attainable, achievable, and practical in most clinical laboratories.

Evaluation of three sample preparation methods for the identification of clinical strains by using two MALDI-TOF MS systems

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has revolutionized the microbial identification, especially in the clinical microbiology laboratories. However, although numerous studies on the identification of microorganisms by MALDI-TOF MS have been reported previously, few studies focused on the effect of pretreatment on identification. Due to the sensitivity of MALDI-TOF MS, different preparation methods will lead to changes in microbial protein fingerprints. In this study, for evaluating a more appropriate preparation method for the clinical microbiology identification, we analyzed the performance of three sample preparation methods on two different MALDI-TOF MS systems. A total of 321 clinical isolates, 127 species, were employed in the comparative study of three different sample preparation methods including the direct colony transfer method (DCTM), the on-target extraction method (OTEM), and the in-tube extraction method (ITEM) compatible with MALDI-TOF MS. All isolates were tested on the Microflex LT and Autof ms1000 devices. The spectra were analyzed using the Bruker biotyper and the Autof ms1000 systems. The results were confirmed by 16/18S rRNA sequencing. Results reveal that the accuracies of isolates identification by Bruker biotyper successfully identified 83.8%, 96.0%, and 95.3% after performing the DCTM, OTEM, and ITEM, respectively, while the Autof ms1000 identified 97.5%, 100%, and 99.7%. These data suggested that the identification rates are comparable among the three preparation methods using the Autof ms1000 and Bruker microflex LT systems but the OTEM is more suitable and necessary for clinical application, owing to its key advantages of simplicity and accuracy.

Misidentification of Candida dubliniensis isolates with the VITEK MS

The phylogenetic relatedness of Candida dubliniensis and C. albicans may lead to misidentification of C. dubliniensis and underestimation of its clinical significance. We evaluated the performance of VITEK-MS in identifying C. dubliniensis isolates following growth on different culture media. Correct identification was documented in 98% of the isolates grown on blood agar media whereas only 44% were correctly identified from SDA or CHROMagar. The use of non-manufacturer validated media for identifying C. dubliniensis with VITEK-MS, may result in misidentification of these isolates as C. albicans. This finding calls for reassessing the accuracy of fungal isolates identification in local workflows using non-validated culture media.

Yeasts in Liquid Swine Diets: Identification Methods, Growth Temperatures and Gas-Formation Potential

Liquid feed is susceptible to microbiological growth. Yeasts are said to cause sudden death in swine due to intestinal gas formation. As not all animals given high yeast content feed fall ill, growth and gas formation potential at body temperature were investigated as possible causally required properties. The best identification method for these environmental yeasts should be tested beforehand. Yeasts derived from liquid diets without (LD - S) and liquid diets with maize silage (LD + S) were examined biochemically (ID32C-test) and with MALDI-TOF with direct smear (DS) and an extraction method (EX). Growth temperature and gas-forming potential were measured. With MALDI-EX, most yeast isolates were identified: Candida krusei most often in LD - S, and C. lambica most often in LD + S, significantly more than in LD - S. Larger colonies, 58.75% of all yeast isolates, were formed at 25 °C rather than at 37 °C; 17.5% of all isolates did not grow at 37 °C at all. Most C. krusei isolates formed high gas amounts within 24 h, whereas none of the C. lambica, C. holmii and most other isolates did. The gas pressure formed by yeast isolates varied more than tenfold. Only a minority of the yeasts were able to produce gas at temperatures common in the pig gut.

Multilocus Sequence Typing Reveals Clonality of Fluconazole-Nonsusceptible Candida tropicalis: A Study From Wuhan to the Global

Candida tropicalis is a globally distributed human pathogenic yeast, and its increasing resistance to azoles makes clinical treatment difficult. In this study, we investigated the clinical features, azole resistance and genetic relatedness of 87 C. tropicalis isolates from central China and combined with the global database to explore the relationship between genetic information and fluconazole susceptibility. Of the 55 diploid sequence types (DSTs) identified by multilocus sequence typing (MLST), 27 DSTs were new to the C. tropicalis MLST database. Fluconazole-nonsusceptible (FNS) isolates were genetically closely related. goeBURST analysis showed that DST225, DST376, DST506, and DST546 formed a distinct and unique FNS clonal complex (CC) in Wuhan. The local FNS CC belongs to the large FNS CC (CC2) in China, in which the putative founder DST225 has been reported from the environment. The three most prevalent types (DST506, DST525, and DST546) in Wuhan had high minimum inhibitory concentrations (MICs) for antifungal azoles, and the six possible nosocomial transmissions we captured were all FNS strains, most of which were from CC2. Unique FNS CCs have been found in Singapore (CC8) and India (CC17) and are close to China's CC2 in the minimum spanning tree. There were no FNS CCs outside Asia. This study is the first to reveal a significant correlation between genetic information and fluconazole susceptibility worldwide and to trace geographical locations, which is of great value for molecular epidemiological surveillance and azole-resistance study of C. tropicalis globally.

Evaluation of Two Commercial Broth Microdilution Methods Using Different Interpretive Criteria for the Detection of Molecular Mechanisms of Acquired Azole and Echinocandin Resistance in Four Common Candida Species

The abilities of the new Vitek 2 AST-YS08 (YS08) and Sensititre YeastOne (SYO) systems to detect the resistances of Candida isolates to azoles and echinocandins were evaluated. In total, 292 isolates, including 28 Candida albicans (6 Erg11 and 2 Fks mutants), 57 Candida parapsilosis (26 Erg11 mutants), 24 Candida tropicalis (10 Erg11 and 1 Fks mutants), and 183 Candida glabrata (39 Pdr1 and 13 Fks mutants) isolates, were tested. The categorical agreements (CAs) between the Clinical and Laboratory Standards Institute (CLSI) method and YS08 fluconazole MICs obtained using clinical breakpoints were 92.4% (C. albicans), 96.5% (C. parapsilosis), and 87.0% (C. tropicalis), and the CAs between the CLSI and SYO MICs were 92.3% (C. albicans), 77.2% (C. parapsilosis), 100% (C. tropicalis), and 98.9% (C. glabrata). For C. glabrata, the CAs with the CLSI micafungin MICs were 92.4% and 55.5% for the YS08 micafungin and caspofungin MICs, respectively; they were 100%, 95.6%, and 98.9% for the SYO micafungin, caspofungin, and anidulafungin MICs, respectively. YS08 does not provide fluconazole data for C. glabrata; the CA with the CLSI fluconazole MIC was 97.8% for the YS08 voriconazole MIC, using an epidemiological cutoff value (ECV) of 0.5 μg/ml. Increased CAs with the CLSI MIC were observed for the YS08 MIC using CLSI ECVs (for fluconazole and C. tropicalis, 100%; for micafungin and C. glabrata, 98.9%) and for the SYO MIC using method-specific ECVs (for fluconazole and C. parapsilosis, 91.2%; for caspofungin and C. glabrata, 98.9%). Therefore, the YS08 and SYO systems may have different abilities to detect mechanisms of azole and echinocandin resistance in four Candida species; the use of method-specific ECVs may improve the performance of both systems.

Molecular epidemiology of Candida tropicalis isolated from urogenital tract infections

Candida tropicalis is a common human pathogenic yeast, and its molecular typing is important for studying the population structure and epidemiology of this opportunistic yeast, such as epidemic genotype, population dynamics, nosocomial infection, and drug resistance surveillance. In this study, the antifungal susceptibility test and multilocus sequence typing (MLST) analysis were carried out on C. tropicalis from central China. Among 64 urogenital isolates, 45 diploid sequence types (DST) were found, of which 20 DSTs (44.4%) were new to the central database. The goeBURST analysis showed that CC1 (clonal complex) was the only azole‐resistant (100%, 10/10) cluster in Wuhan, which was composed of DST546, DST225, DST376, and DST506, and most of the strains (90%, 9/10) were isolated from the urinary tract. Potential nosocomial infections were mainly caused by CC1 strains. The azole resistance rate of urinary isolates (50.0%, 21/42) was higher than that of vaginal isolates (27.3%, 6/22). The genotype diversity and novelty of vaginal isolates were higher than those of urinary isolates. C. tropicalis population in Wuhan was genetically diverse and divergent from that seen in other countries. In this study, there were significant differences in genotype and azole susceptibility between urine and vaginal strains. The azole‐resistant cluster (CC1) found in urine is of great significance for the clinical treatment and prevention of nosocomial infection. The newly discovered DSTs will contribute to further study the similarity, genetic relationship, and molecular epidemiology of C. tropicalis worldwide.

Matrix-assisted laser desorption ionization time-of-flight mass spectrometry combined with UF-5000i urine flow cytometry to directly identify pathogens in clinical urine specimens within 1 hour

Background

Urinary tract infection (UTI) is one of the most common hospital-associated infectious. The traditional laboratory diagnosis method for UTI requires at least 24 hours, and it cannot provide the etiology basis for the clinic in time. The aim of our study is to develop a new method for pathogenic diagnosis of UTI by combining matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) and UF-5000i from urine samples directly within 1 hour.

Methods

A total of 1,503 urine samples were collected from patients suggesting symptoms of UTI from August 2018 to January 2019. Each of these samples was divided into three aliquots. The first aliquot was used for conventional cleaning mid-stream urine culture; the second one for UF-5000i analysis to screen out the bacterial counts, which were more than 1×10⁵ bacteria/mL. The third one was processed to bacterial purification and directly identified by the MALDI-TOF MS.

Results

In our study, 296 of 1,503 urine specimens were screened out by UF-5000i (bacterial pellets counts ≥10⁵/mL). Compared the conventional culture-dependent method, the results of our methods were consistent in 249 of 263 (94.7%) cases, and they were both single-microorganism. Among 249 credible results, species-level identification (score ≥2.0) was contained 233 (233/249. 93.6%), 16 (16/249, 6.4%) samples scored between 1.7 and 1.99, and 14 (14/249, 5.6%) samples scored <1.7 or no peaks found. When there were 2 different kinds of bacteria in the urine, the result of MALDI-TOF MS was unreliable.

Conclusions

MALDI-TOF MS combined with UF-5000i to identify the pathogenic bacteria in urine directly is a novel and reliable method and saves at least 23 hours relative to the current routine conventional method. Thus its rapid and accurate detection may provide the basis of etiology for clinical diagnosis of UTIs efficiently.

Candida auris Clinical Isolates from South Korea: Identification, Antifungal Susceptibility, and Genotyping

Candida auris is an emerging worldwide fungal pathogen. Over the past 20 years, 61 patient isolates of C. auris (4 blood and 57 ear) have been obtained from 13 hospitals in Korea. Here, we reanalyzed those molecularly identified isolates using two matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) systems, including Biotyper and Vitek MS, followed by antifungal susceptibility testing, sequencing of the ERG11 gene, and genotyping. With a research-use-only (RUO) library, 83.6% and 93.4% of the isolates were correctly identified by Biotyper and Vitek MS, respectively. Using an in vitro diagnostic (IVD) library of Vitek MS, 96.7% of the isolates were correctly identified. Fluconazole-resistant isolates made up 62.3% of the isolates, while echinocandin- or multidrug-resistant isolates were not found. Excellent essential (within two dilutions, 96.7%) and categorical agreements (93.4%) between the Clinical and Laboratory Standards Institute (CLSI) and Vitek 2 (AST-YS07 card) methods were observed for fluconazole. Sequencing ERG11 for all 61 isolates revealed that only 3 fluconazole-resistant isolates showed the Erg11p amino acid substitution K143R. All 61 isolates showed identical multilocus sequence typing (MLST). Pulsed-field gel electrophoresis (PFGE) analyses revealed that both blood and ear isolates had the same or similar patterns. These results show that MALDI-TOF MS and Vitek 2 antifungal susceptibility systems can be reliable diagnostic tools for testing C. auris isolates from Korean hospitals. The Erg11p mutation was seldom found among Korean isolates of C. auris, and multidrug resistance was not found. Both MLST and PFGE analyses suggest that these isolates are genetically similar.

The expanding use of matrix-assisted laser desorption/ionization-time of flight mass spectroscopy in the diagnosis of patients with mycotic diseases

INTRODUCTION

Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has emerged as a powerful new tool to identify human fungal pathogens and has radically altered the diagnostic mycology workflow at many medical centers around the world. Areas covered: While most experience is with the identification of yeasts, including species of Candida and Cryptococcus, there is ongoing work investigating the role of MALDI-TOF MS to detect molds, including species of Aspergillus, Fusarium, Scedosporium, and Mucormyctes as well as thermally dimorphic fungi. Expert commentary: In this paper, we review the current knowledge about this important new platform and examine how its expanding use may impact molecular diagnostics and patient care in the years ahead.

A Moldy Application of MALDI: MALDI-ToF Mass Spectrometry for Fungal Identification

As a result of its being inexpensive, easy to perform, fast and accurate, matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-ToF MS) is quickly becoming the standard means of bacterial identification from cultures in clinical microbiology laboratories. Its adoption for routine identification of yeasts and even dimorphic and filamentous fungi in cultures, while slower, is now being realized, with many of the same benefits as have been recognized on the bacterial side. In this review, the use of MALDI-ToF MS for identification of yeasts, and dimorphic and filamentous fungi grown in culture will be reviewed, with strengths and limitations addressed.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometric identification and antifungal susceptibility analysis of Candida species isolated from patients with invasive yeast infections in five university hospitals

In this multicenter study, we compared the performance of the Bruker Biotyper MS system and VITEK 2 YST systems for invasive yeast identification, investigated the distribution of isolated species, and evaluated the antifungal susceptibility profiles of Candida albicans, Candida parapsilosis, and Candida tropicalis. In cases of discrepant results lack of identification with either method, molecular identification techniques were employed. We tested 216 clinical isolates, and concordance between the two methods was observed for 192/216 isolates (88.9%). For five unidentified strains (2.3%), an internal transcribed spacer (ITS) sequencing approach was used. In brief, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-ToF MS) provided short turnaround times and more reliable results than those of Vitek 2 YST. In Wuhan, C. albicans, C. parapsilosis, Candida glabrata, and C. tropicalis were the most common pathogens (93.0%) in patients with candidemia. Cryptococcus neoformans was mainly detected in cerebrospinal fluid samples (88.9%). Trichosporon asahii were all isolated from drainage fluids in the Surgery. Candida albicans was clearly susceptible to azoles, while C. parapsilosis and C. tropicalis displayed differences in susceptibility to azoles. Our findings provide a basis for the practical application of MALDI-ToF MS for identification and for the use of ATB FUNGUS 3 to characterize the susceptibility of Candida spp., thereby providing significant data for therapeutic decisions.

Candidemia in the cancer patient: diagnosis, treatment, and future directions

INTRODUCTION

The presence of Candida species in the blood is known as candidemia and may constitute a medical emergency for patients with cancer. Despite advances in diagnosis and treatment of this fungal infection, mortality remains unacceptably high. Areas covered: This paper reviews recent advances in molecular diagnostics to detect species of Candida as well as novel antifungal agents that have been developed to address candidiasis. We also review prophylaxis strategies to prevent candidiasis in high-risk cancer patients. Expert commentary: We draw from our own experiences treating candidemia in the cancer patient and review novel diagnostic strategies involving molecular resonance and mass spectroscopy. We also explore novel chemoprophylaxis and treatment options, including new drugs such as rezafungin and SCY-078. We also look ahead, to examine how this condition will be managed in the years ahead.

Evaluation of a new matrix-assisted laser desorption/ionization time-of-flight mass spectrometry system for the identification of yeast isolation

BACKGROUND

Currently, three commercial in vitro diagnostic matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) systems are widely used in clinical laboratories. The ASTA MicroIDSys system (ASTA Inc, South Korea) is a newly developed MALDI-TOF MS system used for the identification of pathogenic microorganisms. In the present study, we assessed the performance of the ASTA MALDI-TOF MS system for the identification of pathogenic yeast from clinical samples.

METHODS

We tested 284 clinical yeast isolates from various clinical specimens using ASTA MALDI-TOF MS, and the results were compared with those using molecular sequencing of the ITS or D1-D2 regions of rDNA and biochemical assays.

RESULTS

A total of 284 isolates were tested and found to be distributed across 14 species including Candida albicans (n = 100) and other yeast species (n = 184). ASTA MALDI-TOF MS correctly identified 95.1% (270/284) of the yeast species compared to molecular sequencing. Among them, 262 isolates showed acceptable MALDI-TOF MS scores (≥140), and 98.1% (257/262) isolates were identified correctly. In addition, among 22 isolates with a MALDI-TOF MS score <140, 59.1% (13/22) of the isolates showed concordance with molecular typing at the species level. Clustering analysis revealed the effectiveness of the new MALDI-TOF MS system for the identification of yeast species.

CONCLUSIONS

ASTA MALDI-TOF MS showed high accuracy in the identification of yeast species; it involves facile sample preparation and extraction procedures. ASTA MALDI-TOF MS is expected to be useful for yeast identification in clinical microbiology laboratories due to its reliability and cost-effectiveness.

Multilocus Sequence Typing (MLST) Genotypes of Candida glabrata Bloodstream Isolates in Korea: Association With Antifungal Resistance, Mutations in Mismatch Repair Gene (Msh2), and Clinical Outcomes

Candida glabrata bloodstream infection (BSI) isolates from a particular geographic area have been reported to comprise a relatively small number of the major sequence types (STs) by multilocus sequence typing (MLST) analysis. Yet little is known about the characteristics of major ST strains of C. glabrata. To address this question in Korea, we investigated antifungal resistance and non-synonymous mutations of the mismatch repair gene (msh2 mutations) in C. glabrata BSI isolates, as well as associated clinical characteristics, and compared the results according to MLST genotype. We assessed a total of 209 C. glabrata BSI isolates from seven hospitals in Korea for 2 years (2009 and 2014). Clinical features of candidemia and their outcomes were analyzed for 185 available cases. According to MLST, ST7 (47.8%) was the most common type, followed by ST3 (22.5%); the remainder represented 28 types of minor STs (29.7%). Fluconazole-resistance (FR) rates for ST7, ST3, and other strains were 9.0% (9/100), 8.5% (4/47), and 4.8% (3/62), respectively, and all were susceptible to amphotericin B and micafungin. All ST7 isolates harbored the V239L mutation in msh2, known to confer hypermutability, while 91.5% of ST3 isolates did not harbor the msh2 mutation. Overall, isolates of the same ST had identical msh2 mutations, with the exception of nine isolates. The msh2 mutations were identified in 68.8% (11/16) of the FR isolates and 67.4% (130/193) of the fluconazole susceptible-dose dependent isolates. There was no significant difference in all clinical characteristics between ST3 and ST7. However, the 30-day mortality of C. glabrata candidemia due to the two major ST (ST3 or ST7) strains was significantly higher than that of candidemia due to other minor ST strains (45.1 vs. 25.0%, p < 0.05). Multivariate logistic regression analysis also showed that two major STs (ST3 and ST7) were independent predictors of 30-day mortality. This study showed for the first time that two STs (ST7 and ST3) were predominant among BSI isolates in Korea, and that C. glabrata BSI isolates belonging to two major MLST genotypes are characterized by higher mortality. In addition, most msh2 mutations align with MLST genotype, irrespective of FR.