Identification and typing of the Candida parapsilosis complex: MALDI-TOF MS vs. AFLP

The Emerging Pathogen Candida metapsilosis: Biological Aspects, Virulence Factors, Diagnosis, and Treatment

Fungal infections represent a constant and growing menace to public health. This concern is due to the emergence of new fungal species and the increase in antifungal drug resistance. Mycoses caused by Candida species are among the most common nosocomial infections and are associated with high mortality rates when the infection affects deep-seated organs. Candida metapsilosis is part of the Candida parapsilosis complex and has been described as part of the oral microbiota of healthy individuals. Within the complex, this species is considered the least virulent; however, the prevalence has been increasing in recent years, as well as an increment in the resistance to some antifungal drugs. One of the main concerns of candidiasis caused by this species is the wide range of clinical manifestations, ranging from tissue colonization to superficial infections, and in more severe cases it can spread, which makes diagnosis and treatment difficult. The study of virulence factors of this species is limited, however, proteomic comparisons between species indicate that virulence factors in this species could be similar to those already described for C. albicans. However, differences may exist, taking into account changes in the lifestyle of the species. Here, we provide a detailed review of the current literature about this organism, the caused disease, and some sharing aspects with other members of the complex, focusing on its biology, virulence factors, the host-fungus interaction, the identification, diagnosis, and treatment of infection.

The first established microsatellite markers to distinguish Candida orthopsilosis isolates and detection of a nosocomial outbreak in China

The infection proportion of Candida orthopsilosis, a member of the C. parapsilosis complex, has increased globally in recent years, and nosocomial outbreaks have been reported in several countries. This study aimed to establish microsatellite loci-based typing method that was able to effectively distinguish among C. orthopsilosis isolates. Three reference C. orthopsilosis genome sequences were analyzed to identify repeat loci. DNA sequences containing over eight bi- or more nucleotide repeats were selected. A total of 51 loci were initially identified, and locus-specific primers were designed and tested with 20 epidemiologically unrelated isolates. Four loci with excellent reproducibility, specificity, and resolution for molecular typing purposes were identified, and the combined discriminatory power (DP, based on 20 epidemiologically unrelated isolates) of these four loci was 1.0. Reproducibility was demonstrated by consistently testing three strains each in triplicate, and stability, demonstrated by testing 10 successive passages. Then, we collected 48 C. orthopsilosis non-duplicate clinical isolates from the China Hospital Invasive Fungal Surveillance Net study to compare the DP of the microsatellite-based typing with internal transcribed spacer (ITS) and amplified fragment length polymorphism (AFLP) typing analyses, using ATCC 96139 as a reference strain. These 49 isolates were subdivided into 12 microsatellite types (COMT1-12), six AFLP types, and three ITS types, while all the isolates with the same COMT belonged to consistent AFLP and ITS type, demonstrating the high DP of our microsatellite-type method. According to our results, COMT12 was found to be the predominant type in China, and COMT5 was the second largest and responsible for causing a nosocomial outbreak. This microsatellite-type method is a valuable tool for the differentiation of C. orthopsilosis and could be vital for epidemiological studies to determine strain relatedness and monitor transmission.

The Role of Fatty Acid Metabolites in Vaginal Health and Disease: Application to Candidiasis

Although the vast majority of women encounters at least one vaginal infection during their life, the amount of microbiome-related research performed in this area lags behind compared to alternative niches such as the intestinal tract. As a result, effective means of diagnosis and treatment, especially of recurrent infections, are limited. The role of the metabolome in vaginal health is largely elusive. It has been shown that lactate produced by the numerous lactobacilli present promotes health by limiting the chance of infection. Short chain fatty acids (SCFA) have been mainly linked to dysbiosis, although the causality of this relationship is still under debate. In this review, we aim to bring together information on the role of the vaginal metabolome and microbiome in infections caused by Candida. Vulvovaginal candidiasis affects near to 70% of all women at least once in their life with a significant proportion of women suffering from the recurrent variant. We assess the role of fatty acid metabolites, mainly SCFA and lactate, in onset of infection and virulence of the fungal pathogen. In addition, we pinpoint where lack of research limits our understanding of the molecular processes involved and restricts the possibility of developing novel treatment strategies.

Metabolic profiling of Candida clinical isolates of different species and infection sources

Candida species are the most common cause of opportunistic fungal infections. Rapid identification and novel approaches for the characterization of these fungi are of great interest to improve the diagnosis and the knowledge about their pathogenic properties. This study aimed to characterize clinical isolates of Candida spp. by proteomics (MALDI-TOF MS) and metabolomics (1H-NMR), and to correlate their metabolic profiles with Candida species, source of infection and different virulence associated parameters. In particular, 49 Candida strains from different sources (blood, n = 15; vagina, n = 18; respiratory tract, n = 16), belonging mainly to C. albicans complex (61%), C. glabrata (20%) and C. parapsilosis (12%) species were used. Several extracellular and intracellular metabolites showed significantly different concentrations among isolates recovered from different sources of infection, as well as among different Candida species. These metabolites were mainly related to the glycolysis or gluconeogenesis, tricarboxylic acid cycle, nucleic acid synthesis and amino acid and lipid metabolism. Moreover, we found specific metabolic fingerprints associated with the ability to form biofilm, the antifungal resistance (i.e. caspofungin and fluconazole) and the production of secreted aspartyl proteinase. In conclusion, 1H-NMR-based metabolomics can be useful to deepen Candida spp. virulence and pathogenicity properties.

Evaluation of Microsatellite Typing, ITS Sequencing, AFLP Fingerprinting, MALDI-TOF MS, and Fourier-Transform Infrared Spectroscopy Analysis of Candida auris

Candida auris is an emerging opportunistic yeast species causing nosocomial outbreaks at a global scale. A few studies have focused on the C. auris genotypic structure. Here, we compared five epidemiological typing tools using a set of 96 C. auris isolates from 14 geographical areas. Isolates were analyzed by microsatellite typing, ITS sequencing, amplified fragment length polymorphism (AFLP) fingerprint analysis, matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS), and Fourier-transform infrared (FTIR) spectroscopy methods. Microsatellite typing grouped the isolates into four main clusters, corresponding to the four known clades in concordance with whole genome sequencing studies. The other investigated typing tools showed poor performance compared with microsatellite typing. A comparison between the five methods showed the highest agreement between microsatellite typing and ITS sequencing with 45% similarity, followed by microsatellite typing and the FTIR method with 33% similarity. The lowest agreement was observed between FTIR spectroscopy, MALDI-TOF MS, and ITS sequencing. This study indicates that microsatellite typing is the tool of choice for C. auris outbreak investigations. Additionally, FTIR spectroscopy requires further optimization and evaluation before it can be used as an epidemiological typing method, comparable with microsatellite typing, as a rapid method for tracing nosocomial fungal outbreaks.

Outbreak of Saprochaete clavata Sepsis in Hematology Patients: Combined Use of MALDI-TOF and Sequencing Strategy to Identify and Correlate the Episodes

Introduction

New fungal species are increasingly reported in immunocompromised patients. Saprochaete clavata (S. clavata), an ascomycetous fungus formerly called Geotrichum clavatum, is intrinsically resistant to echinocandins and is often misidentified.

Objective

We describe a cluster of seven S. clavata infections in hospitalized hematology patients who developed this rare fungemia within a span of 11 months. Three of the seven patients died. Identification of the isolates was determined only with the Saramis database of VitekMS system and sequencing of the internal transcribed spacer (ITS) region. Clonal relatedness of the isolates was determined by matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF) analysis; clonal correlation between the strains was investigated by means of phylogenetic analysis, based on single-nucleotide variants (SNPs). Clinical presentation, 1–3 β-D-glucan (BG) and galactomannan (GM) antigen results and analysis of possible sources of contamination are also described with a prospective case–control study of the outbreak.

Results

MALDI-TOF MS-Vitek (bioMerieux, Marcy l’Etoile, France) failed to identify the six isolates, while SARAMIS (bioMerieux, Marcy l’Etoile, France) identified the isolates as S. clavata. Initially, Vitek 2 identified the strains as Geotrichum capitatum in two of the seven cases. Molecular identification gave 99% homology with S. clavata. BG was positive in three out of six patients (range 159 to >523 pg/ml), GM results were always negative. All the isolates were resistant to echinocandins (anidulafungin, micafungin, and caspofungin) and Fluconazole, but susceptible to Flucytosine and Voriconazole. One isolate showed acquired resistance to Flucytosine and Amphotericin B during treatment. Both the correlation-based dendrograms obtained by MALDI-TOF MS (Bruker Daltonics) and MS-Vitek not only clustered six of the seven bloodstream infection (BSI) isolates in the same group, but also showed their strong relatedness. Phylogenetic analysis using SNPrelate showed that the seven samples recorded during the investigation period clustered together. We observed a split between one case and the remainder with a node supported by a z-score of 2.3 (p-value = 0.021) and 16 mutations unique to each branch.

Conclusion

The use of proteomics for identification and evaluation of strain clonality in outbreaks of rare pathogens is a promising alternative to laborious and time-consuming molecular methods, even if molecular whole-genome sequencing (WGS) typing will still remain the reference method for rare emergent pathogens.

BIOF-HILO Assay: A New MALDI-TOF Mass Spectrometry Based Method for Discriminating Between High- and Low-Biofilm-Producing Candida parapsilosis Isolates

Candida parapsilosis is the most frequent cause of catheter-related candidemia among non-Candida albicans species. This may be related to intrinsic capabilities as adhering and forming a biofilm on abiotic surfaces such as on medical devices. As previously demonstrated, patients infected with high biofilm-producing C. parapsilosis isolates had a greater mortality risk compared to patients infected with low biofilm-producing C. parapsilosis isolates. We developed the BIOF–HILO assay, a MALDI–TOF mass spectrometry (MS)-based assay, which compares mass spectra obtained from attached and suspended isolate cells during the early (i.e., 3-h) adhesion phase of in vitro biofilm formation. The composite correlation index (CCI) analysis was used to discriminate between mass spectra differences of the two cell types, classifying all 50 C. parapsilosis clinical isolates, included in the study, after only 3-h of testing, in high or low biofilm producers. All high (n = 25) or low (n = 25) biofilm producers had, according to CCI mass spectra comparison values, higher or lower than one CCI ratios, which were obtained by dividing the CCI_{suspended cells} by the CCI_{attached cells}. In conclusion, the BIOF–HILO assay allows a rapid categorization of C. parapsilosis clinical isolates in high or low biofilm producers. This information, if timely provided to physicians, may improve treatment outcomes in patients with C. parapsilosis candidemia.

Molecular Identification, Genotypic Diversity, Antifungal Susceptibility, and Clinical Outcomes of Infections Caused by Clinically Underrated Yeasts, Candida orthopsilosis, and Candida metapsilosis: An Iranian Multicenter Study (2014-2019)

Despite the increasing occurrence of Candida orthopsilosis and Candida metapsilosis in clinical settings, little is known about their microbiological and clinical properties. Herein, we conducted a national retrospective study (2014–2019) from multiple centers in Iran. Among the 1,770 Candida isolates collected, we identified 600 Candida parapsilosis species complex isolates. Isolate identification was performed by 9-plex PCR, matrix-assisted laser desorption-time of flight mass spectrometry (MALDI-TOF MS), and rDNA sequencing, and antifungal susceptibility testing (AFST) followed CLSI M27-A3/S4; genotyping was performed by amplified fragment length polymorphism (AFLP) analysis; and clinical information was mined. Thirty-one isolates of C. orthopsilosis from various clinical sources, one mixed sample (blood) concurrently containing C. orthopsilosis and C. parapsilosis and one isolate of C. metapsilosis from a nail sample were identified. Although both 9-plex PCR and MALDI-TOF successfully identified all isolates, only 9-plex PCR could identify the agents in a mixed sample. For the C. orthopsilosis isolates, resistance (non-wild type) was noted only for itraconazole (n = 4; 12.5%). Anidulafungin and fluconazole showed the highest and voriconazole had the lowest geometric mean values. AFLP analysis showed three main and four minor genotypes. Interestingly, 90% of nail isolates clustered with 80% of the blood isolates within two clusters, and four blood isolates recovered from four patients admitted to a hospital clustered into two genotypes and showed a high degree of similarity (>99.2%), which suggests that C. orthopsilosis disseminates horizontally. Supported by our data and published case studies, C. orthopsilosis and C. metapsilosis can be linked to challenging clinical failures, and successful outcomes are not always mirrored by in vitro susceptibility. Accordingly, conducting nationwide studies may provide more comprehensive data, which is required for a better prognosis and clinical management of patients.

Identification of nine cryptic species of Candida albicans, C. glabrata, and C. parapsilosis complexes using one-step multiplex PCR

Background

Candida albicans, Candida glabrata, and Candida parapsilosis are three prevalent causes of candidiasis, worldwide. These species are considered as nine medically important complex species. Limited knowledge about these newly recognized species prompted us to develop a one-step, multiplex PCR to detect and identify them in clinical settings.

Methods

Primers targeting Hyphal Wall Protein I gene for the C. albicans, C. dubliniensis, C. africana, Intergenic Spacer for the C. glabrata, C. nivariensis, C. bracarensis, and Intein and ITS rDNA for the C. parapsilosis, C. orthopsilosis, and C. metapsilosis were designed. Using 168 CBS reference strains and 280 clinical isolates, the specificity and reproducibility of the developed assay were evaluated.

Results

Our developed assay successfully identified and distinguished all the nine species. No cross-reaction with closely- and distantly-related yeast species, Aspergillus species and human DNA was observed, resulting in 100% specificity. The ambiguous results obtained by MALDI-TOF for C. albicans and C. africana were corrected by our 9-plex PCR assay. This assay identified all the cryptic complex species from two test sets from Iran and China, correctly.

Conclusions

Our developed multiplex assay is accurate, specific, cost/time-saving, and works without the tedious DNA extraction steps. It could be integrated into routine clinical laboratories and as a reliable identification tool and has the potential to be implemented into epidemiological studies to broaden the limited knowledge of cryptic species complexes.

Electronic supplementary material

The online version of this article (10.1186/s12879-018-3381-5) contains supplementary material, which is available to authorized users.

[Identification of Candida yeasts: Conventional methods and MALDI-TOF MS]

BACKGROUND

Invasive fungal infections are increasing, and Candida yeasts are the main cause. Species other than Candida albicans are becoming more frequent, and some of them may have variable patterns of susceptibility to antifungal agents, making it important to identify them correctly. Conventional identification methods used by most laboratories may present with drawbacks. Mass spectrometry (MALDI-TOF MS) has emerged as an alternative method.

AIMS

The aim of this study was to evaluate the concordance of the identification, at species level, by conventional methods (API) and MALDI-TOF MS.

METHODS

The following species and number of isolates were studied: Candida parapsilosis (28), Candida glabrata (34), Candida krusei (24), Candida tropicalis (45), Candida guilliermondii (30), C. albicans (28), Candida dubliniensis (6), Candida kefyr (1), and Candida lipolytica (1) from the strain collection of Autonomous City of Buenos Aires Mycology Network (RMCABA). The strains C. parapsilosis 22019, C. glabrata 90030, C. krusei 6258 and C. albicans 68548 from the American Type Culture Collection (ATCC) were also included. Discrepancies were resolved by genotyping.

RESULTS AND CONCLUSIONS

The direct concordance between the conventional identification method and MALDI-TOF MS was 92.5% (186/201).

Lodderomyces elongisporus: a bloodstream pathogen of greater clinical significance

The true clinical significance of Lodderomyces elongisporus remains underestimated as a result of problems associated with its identification by the VITEK 2 yeast identification system. Here we describe a case of L. elongisporus primary progressive fungaemia in a woman with no known risk factors for invasive fungal infections. The isolate was identified by PCR sequencing of the internally transcribed spacer region of ribosomal DNA. Despite treatment with caspofungin, the patient died within 3 days of onset of fungaemia. Our literature review highlights this organism's emerging role as a bloodstream pathogen. A need for application of molecular methods for its accurate identification is emphasized.

Microsatellite genotyping of clinical Candida parapsilosis isolates

Background and Purpose:

Candida parapsilosis is a predominant species found in nosocomial infection, particularly in hospitalized patients. The molecular epidemiology of the clinical strains of this species has not been well studied. The present study was performed with the aim of investigating the microsatellite genotyping of Candida parapsilosis among the Iranian clinical isolates.

Materials and Methods:

This study was conducted on 81 independent clinical C. parapsilosis isolates that were genotyped by using a panel of six microsatellite markers.

Results:

The short tandem repeat (STR) typing of clinical C. parapsilosis isolates demonstrated 68 separate genotypes, among which 57 genotypes were observed once and the remaining 11 cases were identified for multiple times. The Simpson’s diversity index for the panel of combined six markers yielded a diversity index of 0.9951. The heterogeneity was observed among the Iranian and the Netherlands clinical C. parapsilosis isolates.

Conclusion:

As the findings indicated, the clinical C. parapsilosis isolates from Iran showed a high genetic diversity. It can be concluded that molecular epidemiology could be useful for screening during outbreak investigation where C. parapsilosis is involved.

Healthcare workers' hands as a vehicle for the transmission of virulent strains of Candida spp.: A virulence factor approach

BACKGROUND

Although the majority of Candida infections are thought to come from endogenous sources, the healthcare workers' (HCWs) hands are being increasingly reported as vehicles for the transmission of pathogens. The aim of the present study was to evaluate the susceptibility of yeast isolated from the HCWs' hands and ICU (Intensive Care Unit) surfaces to antifungal agents and to determine the virulence potential and the genetic similarity between the same.

METHODS

The susceptibility of yeasts from the HCWs' hands (n = 57) and ICU surfaces (n = 98) to conventional antifungals (fluconazole, voriconazole, amphotericin B and micafungin) was evaluated using the broth microdilution assay accordance with CLSI M27-A3. Additionally, some virulence factors such as adhesion and biofilm capacity on abiotic surfaces and on endothelial cells were evaluated, as well as germ tube formation. The similarity among yeast isolates were evaluated by the RAPD technique using the P4, OPA18 and OPE18 primers.

RESULTS

Five species of Candida were found on the HCWs' hands (C. albicans, C. parapsilosis (sensu stricto), C. glabrata, C. tropicalis and C. krusei) and two on ICU surfaces (C. albicans and C. parapsilosis (sensu stricto)). The isolates from hands had higher resistance rates, with C. glabrata having the highest indices (100% FLU; 100% MFG). The similarity of C. albicans from HCWs and ICU surfaces was ≥80% according to the three primers analyzed. Candida spp. from hands had a greater potential for adhesion and biofilm formation on abiotic surfaces (p < 0.05). C. albicans from ICU surfaces had the greatest potential of adhesion on endothelial cells after 2 and 24 h, and presented high filamentation in SEM images and formed more and larger germ tubes (p < 0.05).

CONCLUSION

the present study showed the significant virulence potential of yeasts transmitted in the hospital environment for the first time. Additionally, healthy people working in the ICU can carry these yeasts, which are capable of surviving in hospital surfaces, on their hands, offering a risk to patients, especially those who are immunocompromised.

Identification of Shiga-Toxigenic Escherichia coli outbreak isolates by a novel data analysis tool after matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

The fast and reliable characterization of bacterial and fungal pathogens plays an important role in infectious disease control and tracking of outbreak agents. DNA based methods are the gold standard for epidemiological investigations, but they are still comparatively expensive and time-consuming. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is a fast, reliable and cost-effective technique now routinely used to identify clinically relevant human pathogens. It has been used for subspecies differentiation and typing, but its use for epidemiological tasks, e. g. for outbreak investigations, is often hampered by the complexity of data analysis. We have analysed publicly available MALDI-TOF mass spectra from a large outbreak of Shiga-Toxigenic Escherichia coli in northern Germany using a general purpose software tool for the analysis of complex biological data. The software was challenged with depauperate spectra and reduced learning group sizes to mimic poor spectrum quality and scarcity of reference spectra at the onset of an outbreak. With high quality formic acid extraction spectra, the software’s built in classifier accurately identified outbreak related strains using as few as 10 reference spectra (99.8% sensitivity, 98.0% specificity). Selective variation of processing parameters showed impaired marker peak detection and reduced classification accuracy in samples with high background noise or artificially reduced peak counts. However, the software consistently identified mass signals suitable for a highly reliable marker peak based classification approach (100% sensitivity, 99.5% specificity) even from low quality direct deposition spectra. The study demonstrates that general purpose data analysis tools can effectively be used for the analysis of bacterial mass spectra.

Comparison of four molecular approaches to identify Candida parapsilosis complex species

Since the description of Candida orthopsilosis and C. metapsilosis in 2005, several methods have been proposed to identify and differentiate these species from C. parapsilosis sensu stricto. Species-specific uniplex polymerase chain reaction (PCR) was performed and compared with sequencing of the D1/D2 region of the LSU 28S rDNA gene, microsatellite typing of C. parapsilosis sensu stricto, and PCR-restriction fragment length polymorphism patterns in the ITS1-5.8S-ITS2 region of the rDNA gene. There was agreement between results of testing of 98 clinical isolates with the four PCR-based methods, with 59 isolates identified as C. parapsilosis sensu stricto, 37 as C. orthopsilosis, and two as C. metapsilosis.

Molecular study of the Candida parapsilosis complex in Sfax, Tunisia

Candida parapsilosis, which was previously considered to be a complex of three genetically distinct groups, has emerged as a significant agent of nosocomial infections. Recently, this complex was separated into three species: C. parapsilosis sensu stricto, C. orthopsilosis, and C. metapsilosis In Tunisia, data pertaining to these fungi are limited. Thus, the purpose of our study was to determine by BanI PCR-RFLP and ITS sequencing, the occurrence of Candida parapsilosis complex among 182 isolates identified as C. parapsilosis by phenotypical methods. C. parapsilosis sensu stricto represented 94.5% of all isolates, while C. metapsilosis and. C. orthopsilosis were identified in 3.3% and 2.2%, respectively. Sequence analysis of internal transcribed spacer region confirmed and revealed only one genotype among the C. parapsilosis sensu stricto strains, three genotypes among six C. metapsilosis strains and two genotypes among four C. orthopsilosis strains.

Recent Progress in the Diagnosis of Pathogenic Candida Species in Blood Culture

Candidemia has become an emerging invasive fungal disease. Prompt treatment with appropriate antifungal agent is crucial to reduce the mortality of candidemia. The conventional blood culture method, which is considered the gold standard for candidemia diagnosis, has a low sensitivity and is time-consuming to perform. Recently, several novel advanced diagnostic methods that have a higher sensitivity and a shorter turnaround time than the conventional blood culture method have been developed for the early detection of Candida in blood samples or in blood culture broth. Most of these newer methods were developed using various molecular techniques, such as matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, peptide nucleic acid fluorescence in situ hybridization, and a number of DNA-based techniques including in-house and commercial polymerase chain reactions. In this article, we review and summarize the novel molecular methods that have been recently used for the detection and identification of Candida organisms in blood specimens.

Simple, Low-Cost Detection of Candida parapsilosis Complex Isolates and Molecular Fingerprinting of Candida orthopsilosis Strains in Kuwait by ITS Region Sequencing and Amplified Fragment Length Polymorphism Analysis

Candida parapsilosis has now emerged as the second or third most important cause of healthcare-associated Candida infections. Molecular studies have shown that phenotypically identified C. parapsilosis isolates represent a complex of three species, namely, C. parapsilosis, C. orthopsilosis and C. metapsilosis. Lodderomyces elongisporus is another species phenotypically closely related to the C. parapsilosis-complex. The aim of this study was to develop a simple, low cost multiplex (m) PCR assay for species-specific identification of C. parapsilosis complex isolates and to study genetic relatedness of C. orthopsilosis isolates in Kuwait. Species-specific amplicons from C. parapsilosis (171 bp), C. orthopsilosis (109 bp), C. metapsilosis (217 bp) and L. elongisporus (258 bp) were obtained in mPCR. Clinical isolates identified as C. parapsilosis (n = 380) by Vitek2 in Kuwait and an international collection of 27 C. parapsilosis complex and L. elongisporus isolates previously characterized by rDNA sequencing were analyzed to evaluate mPCR. Species-specific PCR and DNA sequencing of internal transcribed spacer (ITS) region of rDNA were performed to validate the results of mPCR. Fingerprinting of 19 clinical C. orthopsilosis isolates (including 4 isolates from a previous study) was performed by amplified fragment length polymorphism (AFLP) analysis. Phenotypically identified C. parapsilosis isolates (n = 380) were identified as C. parapsilosis sensu stricto (n = 361), C. orthopsilosis (n = 15), C. metapsilosis (n = 1) and L. elongisporus (n = 3) by mPCR. The mPCR also accurately detected all epidemiologically unrelated C. parapsilosis complex and L. elongisporus isolates. The 19 C. orthopsilosis isolates obtained from 16 patients were divided into 3 haplotypes based on ITS region sequence data. Seven distinct genotypes were identified among the 19 C. orthopsilosis isolates by AFLP including a dominant genotype (AFLP1) comprising 11 isolates recovered from 10 patients. A rapid, low-cost mPCR assay for detection and differentiation of C. parapsilosis, C. orthopsilosis, C. metapsilosis and L. elongisporus has been developed.

Evidence of genotypic diversity among Candida auris isolates by multilocus sequence typing, matrix-assisted laser desorption ionization time-of-flight mass spectrometry and amplified fragment length polymorphism

Candida auris is a multidrug-resistant nosocomial bloodstream pathogen that has been reported from Asian countries and South Africa. Herein, we studied the population structure and genetic relatedness among 104 global C. auris isolates from India, South Africa and Brazil using multilocus sequence typing (MLST), amplified fragment length polymorphism (AFLP) fingerprinting and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). RPB1, RPB2 and internal transcribed spacer (ITS) and D1/D2 regions of the ribosomal DNA were sequenced for MLST. Further, genetic variation and proteomic assessment was carried out using AFLP and MALDI-TOF MS, respectively. Both MLST and AFLP typing clearly demarcated two major clusters comprising Indian and Brazilian isolates. However, the South African isolates were randomly distributed, suggesting different genotypes. MALDI-TOF MS spectral profiling also revealed evidence of geographical clustering but did not correlate fully with the genotyping methods. Notably, overall the population structure of C. auris showed evidence of geographical clustering by all the three techniques analysed. Antifungal susceptibility testing by the CLSI microbroth dilution method revealed that fluconazole had limited activity against 87% of isolates (MIC90, 64 mg/L). Also, MIC90 of AMB was 4 mg/L. Candida auris is emerging as an important yeast pathogen globally and requires reproducible laboratory methods for identification and typing. Evaluation of MALDI-TOF MS as a typing method for this yeast is warranted.

Pushing the Limits of MALDI-TOF Mass Spectrometry: Beyond Fungal Species Identification

Matrix assisted laser desorption ionization time of flight (MALDI-TOF) is a powerful analytical tool that has revolutionized microbial identification. Routinely used for bacterial identification, MALDI-TOF has recently been applied to both yeast and filamentous fungi, confirming its pivotal role in the rapid and reliable diagnosis of infections. Subspecies-level identification holds an important role in epidemiological investigations aimed at tracing virulent or drug resistant clones. This review focuses on present and future applications of this versatile tool in the clinical mycology laboratory.

MALDI-TOF typing highlights geographical and fluconazole resistance clusters in Candida glabrata

Utilizing matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectra for Candida glabrata typing would be a cost-effective and easy-to-use alternative to classical DNA-based typing methods. This study aimed to use MALDI-TOF for the typing of C. glabrata clinical isolates from various geographical origins and test its capacity to differentiate between fluconazole-sensitive and -resistant strains.Both microsatellite length polymorphism (MLP) and MALDI-TOF mass spectra of 58 C. glabrata isolates originating from Marseilles (France) and Tunis (Tunisia) as well as collection strains from diverse geographic origins were analyzed. The same analysis was conducted on a subset of C. glabrata isolates that were either susceptible (MIC ≤ 8 mg/l) or resistant (MIC ≥ 64 mg/l) to fluconazole.According to the seminal results, both MALDI-TOF and MLP classifications could highlight C. glabrata population structures associated with either geographical dispersal barriers (p < 10(-5)) or the selection of antifungal drug resistance traits (<10(-5)).In conclusion, MALDI-TOF geographical clustering was congruent with MPL genotyping and highlighted a significant population genetic structure according to fluconazole susceptibility in C. glabrata. Furthermore, although MALDI-TOF and MLP resulted in distinct classifications, MALDI-TOF also classified the isolates with respect to their fluconazole susceptibility profile. Further prospective studies are required to evaluate the capacity of MALDI-TOF typing to investigate C. glabrata infection outbreaks and predict the antifungal susceptibility profile of clinical laboratory isolates.

Current methods for identifying clinically important cryptic Candida species

In recent years, the taxonomy of the most important pathogenic Candida species (Candida albicans, Candida parapsilosis and Candida glabrata) has undergone profound changes due to the description of new closely-related species. This has resulted in the establishment of cryptic species complexes difficult to recognize in clinical diagnostic laboratories. The identification of these novel Candida species seems to be clinically relevant because it is likely that they differ in virulence and drug resistance. Nevertheless, current phenotypic methods are not suitable to accurately distinguish all the species belonging to a specific cryptic complex and therefore their recognition still requires molecular methods. Since traditional mycological techniques have not been useful, a number of molecular based methods have recently been developed. These range from simple PCR-based methods to more sophisticated real-time PCR and/or MALDI-TOF methods. In this article, we review the current methods designed for discriminating among closely related Candida species by highlighting, in particular, the limits of the existing phenotypic tests and the development of rapid and specific molecular tools for their proper identification.

Comparison of MALDI-TOF mass spectra with microsatellite length polymorphisms in Candida albicans

Candida albicans is the most frequent yeast involved in human infections. Its population structure can be divided into several genetic clades, some of which have been associated with antifungal susceptibility. Therefore, detecting and monitoring fungal clones in a routine laboratory setting would be a major epidemiological advance. Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectra results are now widely used as bar codes to identify microorganisms in clinical microbiology laboratories. This study aimed at testing MALDI-TOF mass spectra bar codes to identify clades among a set of C. albicans isolates. Accordingly, 102 clinical strains were genotyped using 10 microsatellite markers and analyzed via MALDI-TOF mass spectrometry. The mass spectra were compared with a reference spectral library including 33 well-characterized collection strains, using a Microflex(TM) system and Biotyper(TM) software, to test the capacity of the spectrum of a given isolate to match with the reference mass spectrum of an isolate from the same genetic clade. Despite high confidence species identification, the spectra failed to significantly match with the corresponding clade (p = 0.74). This was confirmed with the MALDI-TOF spectra similarity dendrogram, in which the strains were dispersed irrespective of their genetic clade. Various attempts to improve intra-clade spectra recognition were unsuccessful. In conclusion, MALDI-TOF mass spectra bar code analysis failed to reliably recognize genetically related C. albicans isolates. Further studies are warranted to develop alternative MALDI-TOF mass spectra analytical approaches to identify and monitor C. albicans clades in the routine clinical laboratory.

Special application of matrix-assisted laser desorption ionization time-of-flight mass spectrometry in clinical microbiological diagnostics

Matrix-assisted laser desorption ionization time-of-flight mass spectrometry as a new possibility for rapid identification of bacteria and fungi revolutionized the clinical microbiological diagnostics. It has an extreme importance in the routine microbiological laboratories, as identification of the pathogenic species rapidly will influence antibiotic selection before the final determination of antibiotic resistance of the isolate. The classical methods for identification of bacteria or fungi, based on biochemical tests, are influenced by many environmental factors. The matrix-assisted laser desorption ionization time-of-flight mass spectrometry is a rapid method which is able to identify a great variety of the isolated bacteria and fungi based on the composition of conserved ribosomal proteins. Recently several other applications of the method have also been investigated such as direct identification of pathogens from the positive blood cultures. There are possibilities to identify bacteria from the urine samples in urinary tract infection or from other sterile body fluids. Using selective enrichment broth Salmonella sp from the stool samples can be identified more rapidly, too. The extended spectrum beta-lactamase or carbapenemase production of the isolated bacteria can be also detected by this method helping the antibiotic selection in some cases. Matrix-assisted laser desorption ionization time-of-flight mass spectrometry based methods are suitable to investigate changes in deoxyribonucleic acid or ribonucleic acid, to carry out rapid antibiotic resistance determination or other proteomic analysis. The aim of this paper is to give an overview about present possibilities of using this technique in the clinical microbiological routine procedures. Orv. Hetil., 2014, 155(38), 1495–1503.

MALDI-TOF mass spectrometry: any use for Aspergilli?

Recently, relentless efforts to develop rapid, cost-effective, and reliable laboratory methods for daily diagnosis of fungal diseases such as aspergillosis appear to be materialized in the relatively new, but revolutionary matrix-assisted laser desorption ionization-time-of-flight (MALDI-TOF) mass spectrometry (MS) technology. As for Aspergilli, MALDI-TOF MS profiling of isolates growing in culture--characteristic protein spectra are obtainable by means of simple and reproducible preanalytical and analytical procedures--ensures that single species within the different sections or complexes can be easily and accurately identified, including species that are morphologically and phylogenetically similar to each other. Thus, resort to longer and more onerous molecular biology techniques is restricted to those cases for which no spectra in the reference fungal database or library are available at the time of analysis. However, it is necessary to interrogate reference libraries composed of spectra that have been obtained using procedures similar to those used to obtain the test isolate's mass spectrum, as well as to continuously update these libraries for enriching them with fungal strains/species not (or not well) represented in their current versions. Compared to mold identification, very limited work was reported on the use of MALDI-TOF MS to perform strain typing or antifungal susceptibility testing for Aspergilli. If these complementing areas will be potentiated in the near future, MALDI-TOF MS could effectively support the clinical microbiology/mycology laboratory in its primary role of assisting either infection control specialists or physicians for the diagnosis and treatment of aspergillosis.