Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry using the Vitek MS system for rapid and accurate identification of dermatophytes on solid cultures

Evaluation of VITEK MS Version 3.0 MALDI-TOF for the identification of anaerobes, mycobacteria, Nocardia, and moulds

PURPOSE

The identification of anaerobes, Mycobacterium and Nocardia species, and moulds by MALDI-TOF-MS remains a challenge. This study aimed to evaluate the performance of MALDI-TOF in the identification of these organisms.

METHODS

A total of 382 strains, comprising 128 (33.5 %) anaerobes, 126(33.0 %) mycobacterial, 113(29.6 %), mycelial fungi, and 15(3.9 %) Nocardia species were evaluated by VITEK MS Version 3.0. The results were compared with the identification of the isolates by DNA sequence analysis. The DNA sequences used for analysis were the 16S rRNA for anaerobic bacteria, hsp65 gene for mycobacteria, whereas both 16S rRNA and hsp65 gene for Nocardia species, and internal transcribed spacer (ITS) and 28S rRNA gene's D1/D2 regions of fungi.

RESULTS

The VITEK-MS accurately identified 78.3 % (299/382) of the strains at the species, and 9.4 % (36/382) at the genus level. Misidentifications were observed in 3.9 % (15/382) isolates. Of isolates tested, 8.4 % (32/382) were not identified by the system, and 7.06 % (27/382) were not included in the IVD database.

CONCLUSION

An upgraded VITEK MS V3.0 database provides reasonably accurate and rapid identification of clinically relevant anaerobes, mycobacteria, Nocardia species, and moulds to the species level.

Seborrheic dermatitis-like adult tinea capitis due to Trichophyton rubrum in an elderly man

Adult tinea capitis is often neglected and misdiagnosed, especially in men. We herein reported an older man with seborrheic dermatitis-like tinea capitis caused by Trichophyton rubrum to raise awareness of the disease. Scale and alopecia were the critical diagnostic clues in this patient. Given the previous presence of tinea pedis and onychomycosis, relevant mycological examinations were promptly performed, and antifungal therapy, as well as patient education, were effectively administered.

Fungal communities on alpine cheese rinds in Southern Switzerland

BACKGROUND

The biodiversity of the mycobiota of soft cheese rinds such as Brie or Camembert has been extensively studied, but scant information is available on the fungi colonizing the rinds of cheese produced in the Southern Switzerland Alps. This study aimed at exploring the fungal communities present on rinds of cheese matured in five cellars in Southern Switzerland and to evaluate their composition with regards to temperature, relative humidity, type of cheese, as well as microenvironmental and geographic factors. We used macro- and microscopical morphology, matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry, and sequencing to characterize the fungal communities of the cheeses, and compared them with metabarcoding targeting the ITS region.

RESULTS

Isolation by serial dilution yielded 201 isolates (39 yeasts and 162 filamentous fungi) belonging to 9 fungal species. Mucor and Penicillium were dominant, with Mucor racemosus, M. lanceolatus, P. biforme, and P. chrysogenum/rubens being the most frequent species. All but two yeast isolates were identified as Debaryomyces hansenii. Metabarcoding detected 80 fungal species. Culture work and metabarcoding produced comparable results in terms of similarity of the fungal cheese rind communities in the five cellars.

CONCLUSIONS

Our study has shown that the mycobiota on the rinds of the cheeses studied is a comparatively species-poor community influenced by temperature, relative humidity, type of cheese, and manufacturing steps, as well as microenvironmental and possibly geographic factors.

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.

Investigations upon the Improvement of Dermatophyte Identification Using an Online Mass Spectrometry Application

Online MALDI-TOF mass spectrometry applications, such as MSI-2, have been shown to help identify dermatophytes, but recurrent errors are still observed between phylogenetically close species. The objective of this study was to assess different approaches to reduce the occurrence of such errors by adding new reference spectra to the MSI-2 application. Nine libraries were set up, comprising an increasing number of spectra obtained from reference strains that were submitted to various culture durations on two distinct culture media: Sabouraud gentamicin chloramphenicol medium and IDFP Conidia medium. The final library included spectra from 111 strains of 20 species obtained from cultures on both media collected every three days after the appearance of the colony. The performance of each library was then analyzed using a cross-validation approach. The spectra acquisitions were carried out using a Microflex Bruker spectrometer. Diversifying the references and adding spectra from various culture media and culture durations improved identification performance. The percentage of correct identification at the species level rose from 63.4 to 91.7% when combining all approaches. Nevertheless, residual confusion between close species, such as Trichophyton rubrum, Trichophyton violaceum and Trichophyton soudanense, remained. To distinguish between these species, mass spectrometry identification should take into account basic morphological and/or clinico-epidemiological features.

The qualitative accuracy of clinical dermatophytes via matrix-assisted laser desorption ionization-time of flight mass spectrometry: a meta-analysis

Dermatophytes are an important part of superficial fungal infections, and accurate diagnosis is paramount for successful treatment. Recently, matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has emerged as a powerful tool to identify clinical pathogens; its advantages are cost-effectiveness, rapid detection, and high accuracy. However, as the accurate identification of clinical dermatophytes via MALDI-TOF MS has still not been fully evaluated, we performed a meta-analysis for systematic evaluation it. Fifteen eligible studies were involved and showed high accuracy with an identification ratio of 0.96 (95%CI = 0.92─1.01) and 0.91 (95%CI = 0.86─0.96) at the genus and species levels, respectively. The results showed higher accuracy ratio of Vitek MS (91%) than MALDI Biotyper (85%). Dermatophytes such as Trichophyton interdigitale (0.99, 95%CI = 0.97─1.02), T. mentagrophytes var interdigitale (1.00, 95%CI = 0.98─1.02), and Microsporum canis (0.97, 95%CI = 0.89─1.04) showed high accuracy in detected clinical dermatophytes. Moreover, a library with self-built database set up by laboratories showed higher accuracy than commercial database, and 15-day cultivation for dermatophytes showed highest accuracy considering culture time. High heterogeneity was observed and decreased only with the subgroup analysis of species. The subgroup analysis of mass spectrometry, library database, and culture time also exhibited high heterogeneity. In summary, our results showed that MALDI-TOF MS could be used for highly accurate detection of clinically pathogenic dermatophytes, which could be an alternative diagnostic method in addition to morphological and molecular methods.

LAY ABSTRACT

This meta-analysis comprehensively investigated the qualitative accuracy of clinical dermatophytes through MALDI-TOF MS. Owing to the high accuracy observed at both genus and species levels, this approach could be an alternative diagnostic method in addition to morphological and molecular methods.

Commercial real time PCR implementation for rapid diagnosis of onychomycosis: A new workflow in a clinical laboratory

INTRODUCTION

Onychomycosis is a frequent and underdiagnosed condition. Approximately 90% of toenail onychomycosis infections are caused by dermatophytes, but classical diagnosis based on culture and microscopy observation is slow and has low sensitivity. Both limitations can be solved incorporating molecular techniques to routine diagnosis of onychomycosis.

OBJECTIVE

Prospective evaluation of the utility of incorporating in the clinical laboratory workflow a commercial real time PCR (qPCR) for dermatophytes detection in nails after potassium hydroxide direct observation screening.

MATERIALS AND METHODS

152 nail samples were included (34 KOH negative and 118 KOH positive) and processed by culture and qPCR.

RESULTS

In the negative KOH group, only one dermatophyte grew in culture and three were detected by qPCR. In the group of positive KOH, 57 dermatophytes grew in culture and 81 were detected by qPCR. In this group, 25% of diagnosed dermatophytes were detected only by qPCR. The sensitivity of qPCR compared to culture is 92.8% and time of response decreases from days to hours.

CONCLUSION

Based in our results, we propose a workflow algorithm for a clinical laboratory that eliminates culture for qPCR positive samples.

An exploratory MALDI-TOF MS library based on SARAMIS superspectra for rapid identification of Aspergillus section Nigri

Matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS) is a broadly used technique for identification and typing of microorganisms. However, its application to filamentous fungi has been delayed. The objective of this study was to establish a data library for rapid identification of the genus Aspergillus sect. Nigri using MALDI-TOF MS. With respect to sample preparation, we compared the utility of using mature mycelia, including conidial structures, to accumulate a wider range of proteins versus the conventional method relying on young hyphae. Mass spectral datasets obtained for 61 strains of 17 species were subjected to cluster analysis and compared with a phylogenetic tree based on calmodulin gene sequences. Specific and frequent mass spectral peaks corresponding to each phylogenetic group were selected (superspectra for the SARAMIS system). Fifteen superspectra representing nine species were ultimately created. The percentage of correct identification for 217 spectra was improved from 36.41% to 86.64% using the revised library. Additionally, 2.76% of the spectra were assigned to candidates that comprised several related species, including the correct species.

Identification of Zoophilic Dermatophytes Using MALDI-TOF Mass Spectrometry

Dermatophytoses represent a major health burden in animals and man. Zoophilic dermatophytes usually show a high specificity to their original animal host but a zoonotic transmission is increasingly recorded. In humans, these infections elicit highly inflammatory skin lesions requiring prolonged therapy even in the immunocompetent patient. The correct identification of the causative agent is often crucial to initiate a targeted and effective therapy. To that end, matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) represents a promising tool. The objective of this study was to evaluate the reliability of species identification of zoophilic dermatophytes using MALDI-TOF MS. The investigation of isolates from veterinary clinical samples suspicious of dermatophytoses suggests a good MALDI-TOF MS based identification of the most common zoophilic dermatophyte Microsporum canis. Trichophyton (T.) spp. usually achieved scores only around the cutoff value for secure species identification because of a small number of reference spectra. Moreover, these results need to be interpreted with caution due to the close taxonomic relationship of dermatophytes being reflected in very similar spectra. In our study, the analysis of 50 clinical samples of hedgehogs revealed no correct identification using the provided databases, nor for zoophilic neither for geophilic causative agents. After DNA sequencing, adaptation of sample processing and an individual extension of the in-house database, acceptable identification scores were achieved (T. erinacei and Arthroderma spp., respectively). A score-oriented distance dendrogram revealed clustering of geophilic isolates of four different species of the genus Arthroderma and underlined the close relationship of the important zoophilic agents T. erinacei, T. verrucosum and T. benhamiae by forming a subclade within a larger cluster including different dermatophytes. Taken together, MALDI-TOF MS proofed suitable for the identification of zoophilic dermatophytes provided fresh cultures are used and the reference library was previously extended with spectra of laboratory-relevant species. Performing independent molecular methods, such as sequencing, is strongly recommended to substantiate the findings from morphologic and MALDI-TOF MS analyses, especially for uncommon causative agents.

Matrix-assisted laser desorption/ionisation-time of flight mass spectrometry: Protocol standardisation, comparison and database expansion for faster and reliable identification of dermatophytes

BACKGROUND

Accurate and early identification of dermatophytes enables prompt antifungal therapy. However, phenotypic and molecular identification methods are time-consuming. MALDI-TOF MS-based identification is rapid, but an optimum protocol is not available.

OBJECTIVES

To develop and validate an optimum protein extraction protocol for the efficient and accurate identification of dermatophytes by MALDI-TOF MS.

MATERIALS/METHODS

Trichophyton mentagrophytes complex (n = 4), T. rubrum (n = 4) and Microsporum gypseum (n = 4) were used for the optimisation of protein extraction protocols. Thirteen different methods were evaluated. A total of 125 DNA sequence confirmed clinical isolates of dermatophytes were used to create and expand the existing database. The accuracy of the created database was checked by visual inspection of MALDI spectra, MSP dendrogram and composite correlation index matrix analysis. The protocol was validated further using 234 isolates.

RESULT

Among 13 protein extraction methods, six correctly identified dermatophytes but with a low log score (≤1.0). The modified extraction protocol developed provided an elevated log score of 1.6. Significant log score difference was observed between the modified protocol and other existing protocols (T. mentagrophytes complex: 1.6 vs. 0.2-1.0, p < .001; T. rubrum: 1.6 vs. 0.4-1.0, p < .001; M. gypseum:1.6 vs. 0.2-1.0, p < .001). Expansion of the database enabled the identification of all 234 isolates (73.5% with log score ≥2.0 and 26.4% with log scores range: 1.75-1.99). The results were comparable to DNA sequence-based identification.

CONCLUSION

MALDI-TOF MS with an updated database and efficient protein extraction protocol developed in this study can identify dermatophytes accurately and also reduce the time for identifying them.

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.

Using MALDI-ToF mass spectrometry to identify mushroom species: Proof of concept analysis of Amanita genus specimens

Food poisoning caused by toxic mushrooms, such as species in the Amanita genus, occurs frequently around the world. To properly treat these patients, it is important to rapidly and accurately identify the causal species. Matrix-assisted laser desorption/ionization time-of-flight (MALDI-ToF) mass spectrometry is a rapid technique that has been used in medical laboratories for the past three decades to identify bacteria, yeasts, and filamentous fungi.Matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-Tof MS) is a rapid method used for the past three decades to identify microorganisms. In this study, we created and internally validated a MALDI-Tof MS reference database comprising 15 Amanita species frequently encountered in France, and we challenged this database with 38 Amanita specimens from four French locations, using a free online application for MALDI-ToF spectra identifications.Assessment of the database showed that mass spectra can be obtained by analyzing any portion of a carpophore and that all portions enabled identification of the carpophore at the species level. Most carpophores were correctly identified using our database, with the exception of specimens from the Vaginatae section. Decay tests also demonstrated that decayed portions (like those found in the kitchen garbage can) of Amanita phalloides mushrooms could be properly identified using MALDI-ToF MS.Our findings provide important insight for toxicology laboratories that often rely on DNA sequencing to identify meal leftovers implicated in food poisoning. In future developments, this technique could also be used to detect counterfeit mushrooms by including other genera in the reference database.

LAY SUMMARY

MALDI-ToF MS is a powerful identification tool for microorganisms. We demonstrate that the technique can be applied to Amanita specimens. This will prevent food intoxications as a rapid and definite identification can be obtained, and it can also be used for food remnants.

Tinea faciei caused by Trichophyton benhamiae in a child

Tinea faciei is a common pediatric skin disease, most often caused by fungi of the genus Trichophyton. T benhamiae has been recently reclassified as a distinct species and is recognized as an emerging zoonotic dermatophyte with a wide range of possible infectious reservoirs worldwide. We present a previously healthy 7-year-old child presenting with unusual inflammatory facial plaques due to T benhamiae, confirmed by mass spectroscopy.

Tinea gladiatorum due to Trichophyton tonsurans in a school wrestling team in Mexico: A case series

Background and Purpose:

Tinea gladiatorum is a type of dermatophytosis that occurs in combat athletes, such as wrestlers and judo fighters, as a result of Trichophyton species. Herein, we aimed to present a small outbreak of tinea gladiatorum in a high school in Mexico.

Materials and Methods:

Seven individuals belonging to the school fighting team were mycologically studied with direct examinations and cultures. In four cases, T. tonsurans was isolated and identified by morphological and proteomic methods (Matrix-assisted laser desorption/ionization- time-of-flight mass spectrometry). Out of the four subjects, two cases had clinical lesions presented as tinea corporis, and two cases were healthy carriers. Trichophyton tonsurans was also isolated from one of the four training mats (25%). All positive patients were treated with systemic or topical antifungals and achieved clinical and mycological cure.

Conclusion:

We report the first outbreak of tinea gladiatorum caused by T. tonsurans among a group of high school wrestlers in Mexico.

Recent trends in rapid diagnostic techniques for dermatophytosis

Dermatophytosis is a common contagious disease of both humans and animals. It is caused by a group of filamentous fungi known as dermatophytes, including several genera and various species. An accurate diagnosis of dermatophytes as a causative agent of a skin lesion requires up to one month of conventional laboratory diagnostics. The conventional gold standard diagnostic method is a direct microscopic examination followed by 3 to 4 weeks of Sabouraud's dextrose agar (SDA) culturing, and it may require further post-culturing identification through biochemical tests or microculture technique application. The laborious, exhaustive, and time-consuming gold standard method was a real challenge facing all dermatologists to achieve a rapid, accurate dermatophytosis diagnosis. Various studies developed more rapid, accurate, reliable, sensitive, and specific diagnostic tools. All developed techniques showed more rapidity than the classical method but variable specificities and sensitivities. An extensive bibliography is included and discussed through this review, showing recent variable dermatophytes diagnostic categories with an illustration of weaknesses, strengths, and prospects.

Epidemiology and Diagnostic Perspectives of Dermatophytoses

Dermatophytoses affect about 25% of the world population, and the filamentous fungus Trichophyton rubrum is the main causative agent of this group of diseases. Dermatomycoses are caused by pathogenic fungi that generally trigger superficial infections and that feed on keratinized substrates such as skin, hair, and nails. However, there are an increasing number of reports describing dermatophytes that invade deep layers such as the dermis and hypodermis and that can cause deep infections in diabetic and immunocompromised patients, as well as in individuals with immunodeficiency. Despite the high incidence and importance of dermatophytes in clinical mycology, the diagnosis of this type of infection is not always accurate. The conventional methods most commonly used for mycological diagnosis are based on the identification of microbiological and biochemical features. However, in view of the limitations of these conventional methods, molecular diagnostic techniques are increasingly being used because of their higher sensitivity, specificity and rapidity and have become more accessible. The most widely used molecular techniques are conventional PCR, quantitative PCR, multiplex PCR, nested, PCR, PCR-RFLP, and PCR-ELISA. Another promising technique for the identification of microorganisms is the analysis of protein profiles by MALDI-TOF MS. Molecular techniques are promising but it is necessary to improve the quality and availability of the information in genomic and proteomic databases in order to streamline the use of bioinformatics in the identification of dermatophytes of clinical interest.

Evaluation of the new Id-Fungi plates from Conidia for MALDI-TOF MS identification of filamentous fungi and comparison with conventional methods as identification tool for dermatophytes from nails, hair and skin samples

OBJECTIVES

We first compare the efficiency of mould/dermatophyte identification by MALDI-TOF MS using a new medium called Id-Fungi plates (IDFP) from Conidia^® and two different databases. For the second purpose, we evaluated a new version of the medium supplemented with cycloheximide, Id-Fungi plates Plus (IDFPC) for the direct inoculation of nails, hair and skin samples and compared the efficiency of MALDI-TOF MS identification of dermatophytes to classical methods based on culture and microscopy.

METHODS

A total of 71 strains have been cultured IDFP and Sabouraud gentamicin plates (SGC2) and were identified by MALDI-TOF MS. For the evaluation of the combination IDFPC/ MALDI-TOF MS as a method of identification for dermatophytes, 428 samples of hair nails and skin were cultivated in parallel on IDFPC and Sabouraud + cycloheximide medium (SAB-ACTI).

RESULTS

For Aspergillus sp and non-Aspergillus moulds, the best performances were obtained on IDFP after maximum 48-h growth, following protein extraction. For dermatophytes, the best condition was using the IDFP at 72 hours, after extended direct deposit. Regarding the direct inoculation of nails, hair skin on IDFPC, 129/428 (30.1%) showed a positive culture against 150/428 (35%) on SAB-ACTI medium. Among the 129 positive strains, the identification by MALDI-TOF MS was correct for 92/129 (71.4%).

CONCLUSION

The IDFP allows the generation of better spectra by MALDI-TOF MS compared to SGC2. It facilitates sampling and deposit. Regarding the use of IDFPC, this medium seems less sensitive than SAB-ACTI but among positive strains, the rate of correct identification by MALDI-TOF MS is satisfactory.

Species identification of dermatophytes isolated in China by matrix-assisted laser desorption ionisation-time-of-flight mass spectrometry

BACKGROUND AND OBJECTIVES

Matrix-assisted laser desorption ionisation-time-of-flight mass spectrometry (MALDI-TOF MS) is a novel technique for identifying dermatophytes. This study aimed to detect the limitation of MALDI-TOF MS applied to dermatophytes.

METHODS

A total of 113 DNA-sequenced dermatophyte isolates preserved at the Research Center for Medical Mycology of Peking University were selected for this study. Forty-two isolates were selected as reference strains used to create a supplementary database. Seventy-one isolates (Trichophyton rubrum series, T benhamiae series, T mentagrophytes series species and T schoenleinii) were used to evaluate the suitability of the MALDI-TOF MS Biotyper system. MALDI Biotyper 4.0 software was employed to construct the main spectrum profile (MSP) dendrograms.

RESULTS

Correct identification rates at the species and genus levels were 90.1% and 91.5%, respectively, using Bruker Filamentous Fungi Library 1.0 combined with the novel database. The MSP dendrogram of the T rubrum series showed unambiguous separation of T rubrum and T violaceum and that of the T benhamiae series distinguished T verrucosum, T benhamiae and T erinacei. Conversely, the MSP dendrogram of the T mentagrophytes series did not successfully distinguish T mentagrophytes, T interdigitale and T tonsurans.

CONCLUSION

MALDI-TOF MS showed good performance in the identification and delineation of the T rubrum series and T benhamiae series, but showed poor performance in T mentagrophytes series.

Detection and identification of dermatophytes based on currently available methods - a comparative study

AIMS

Accurate identification of dermatophytes is essential for implementing appropriate antifungal treatment and epidemiological analysis. However, the limitations of conventional diagnostics are a frequently discussed topic, and new diagnostic techniques are constantly expanding. In this study, we assess the suitability of conventional diagnostic techniques in comparison to the real-time PCR assay and MALDI-TOF MS in detection and identification of dermatophytes.

METHODS AND RESULTS

Strains included in this study were obtained from human and animals with symptomatic, and asymptomatic infection. A direct examination revealed that 31·7 and 60·9% of samples from symptomatic patients, and 25·7 and 60% from asymptomatic animals were positive, as shown by light and fluorescence microscopy respectively. In turn, dermatophytes were isolated from 90·2 and 71·4% of these samples. The pan-dermatophyte primers in real-time PCR assay facilitated detection in 85·3 and 82·9% of the symptomatic and asymptomatic dermatophytoses respectively. Additionally, species-specific PCR assays were positive in 70·7 and 37·1% of these samples. The MALDI-TOF MS analysis yielded positive results consistent with conventional techniques in 97·2 and 72% of symptomatic and asymptomatic infections respectively.

CONCLUSIONS

Our study revealed that there is no universal diagnostic method that would be ideal in each of the cases considered. Nonetheless, conventional techniques are still the most effective and reliable tools for mycological diagnostics.

SIGNIFICANCE AND IMPACT OF THE STUDY

Dermatologists and veterinarians have difficulties in making a diagnosis of dermatophytoses based only on observed symptoms of fungal infections, as they mimic symptoms of other dermatoses. In this context, a comparative analysis of the results of diagnostics performed using conventional methods and new technologies are crucial for implementing these pioneer methods into routine laboratory practice.

Commercial real time PCR implementation for rapid diagnosis of onychomycosis: A new workflow in a clinical laboratory

INTRODUCTION

Onychomycosis is a frequent and underdiagnosed condition. Approximately 90% of toenail onychomycosis infections are caused by dermatophytes, but classical diagnosis based on culture and microscopy observation is slow and has low sensitivity. Both limitations can be solved incorporating molecular techniques to routine diagnosis of onychomycosis.

OBJECTIVE

Prospective evaluation of the utility of incorporating in the clinical laboratory workflow a commercial real time PCR (qPCR) for dermatophytes detection in nails after potassium hydroxide direct observation screening.

MATERIALS AND METHODS

152 nail samples were included (34 KOH negative and 118 KOH positive) and processed by culture and qPCR.

RESULTS

In the negative KOH group, only one dermatophyte grew in culture and three were detected by qPCR. In the group of positive KOH, 57 dermatophytes grew in culture and 81 were detected by qPCR. In this group, 25% of diagnosed dermatophytes were detected only by qPCR. The sensitivity of qPCR compared to culture is 92.8% and time of response decreases from days to hours.

CONCLUSION

Based in our results, we propose a workflow algorithm for a clinical laboratory that eliminates culture for qPCR positive samples.

Increased species-assignment of filamentous fungi using MALDI-TOF MS coupled with a simplified sample processing and an in-house library

In this study we evaluated the capacity of MALDI-TOF MS (Bruker Daltonics, Bremen, Germany) to identify clinical mould isolates. We focused on two aspects of MALDI-TOF MS identification: the sample processing and the database. Direct smearing of the sample was compared with a simplified processing consisting of mechanical lysis of the moulds followed by a protein extraction step. Both methods were applied to all isolates and the Filamentous Fungi Library 1.0 (Bruker Daltonics) was used for their identification. This approach allowed the correct species-level identification of 25/34 Fusarium spp. and 10/10 Mucor circinelloides isolates using the simplified sample processing. In addition, 7/34 Fusarium spp. and 1/21 Pseudallescheria/Scedosporium spp. isolates were correctly identified at the genus level. The remaining isolates-60-could not be identified using the commercial database, mainly because of the low number of references for some species and the absence of others. Thus, an in-house library was built with 63 local isolates previously characterized using DNA sequence analysis. Its implementation allowed the accurate identification at the species level of 94 isolates (91.3%) and the remaining nine isolates (8.7%) were correctly identified at the genus level. No misidentifications at genus level were detected. In conclusion, with improvements of both the sample preparation and the feeding of the database, MALDI-TOF MS is a reliable, ready to use method to identify moulds of clinical origin in an accurate, rapid, and cost-effective manner.

Identification of clinical dermatophyte isolates obtained from Iran by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

BACKGROUND AND PURPOSE

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is widely used to discriminate among pathogenic microorganisms in clinical laboratories. The aim of this study was to assess the utility of MALDI-TOF MS in the routine identification of clinical dermatophyte isolates obtained from various geographical regions of Iran.

MATERIALS AND METHODS

A total of 94 isolates, including Trichophyton interdigitale (n=44), T. rubrum (n=40), T. tonsurans (n=4), Microsporum canis (n=4), and Epidermophyton floccosum (n=1), were analyzed in this study. The identity of each isolate was determined by polymerase chani reaction amplification and sequencing of the internal transcribed spacer (ITS) region of nuclear-encoded ribosomal DNA and also MALDI-TOF MS. The obtained data by molecular approach were compared with MALDI-TOF MS.

RESULTS

The MALDI-TOF MS led to the identification of 44 (47%) isolates at the species level by generating the spectral score values of ≥ 2.0. However, there was not sufficient agreement between the results of the molecular-based ITS identification methods and MALDI-TOF MS in the species identification of 16 (17%) isolates. The Bruker Daltonics database was also not able to identify protein spectra related to 12 isolates (13%), including T. interdigitale (n=5), T. rubrum (n=4), M. canis (n=2), and T. tonsurans (n=1).

CONCLUSION

According to the results, the utility of MALDI-TOF MS as a routine diagnostic tool for the accurate and reliable identification of dermatophytes can be justified whenever the protein spectra of a large set of worldwide clinical isolates are included in the commercial libraries. In addition, MALDI-TOF MS can be alternatively used to construct an in-house reference database.

Rapid characterization of aquatic hyphomycetes by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Protein fingerprinting using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI--TOF MS) is a rapid, reliable, and economical method to characterize isolates of terrestrial fungi and other microorganisms. The objective of our study was to evaluate the suitability of MALDI-TOF MS for the identification of aquatic hyphomycetes, a polyphyletic group of fungi that play crucial roles in stream ecosystems. To this end, we used 34 isolates of 21 aquatic hyphomycete species whose identity was confirmed by spore morphology and internal transcribed spacer (ITS1-5.8S-ITS2 = ITS) nuc rDNA sequencing. We tested the efficiency of three protein extraction methods, including chemical and mechanical treatments using 13 different protocols, with the objective of producing high-quality MALDI-TOF mass spectra. In addition to extraction protocols, mycelium age was identified as a key parameter affecting protein extraction efficiency. The dendrogram based on mass-spectrum similarity indicated good and relevant taxonomic discrimination; the tree structure was comparable to that of the phylogram based on ITS sequences. Consequently, MALDI-TOF MS could reliably identify the isolates studied and provided greater taxonomic accuracy than classical morphological methods. MALDI-TOF MS seems suited for rapid characterization and identification of aquatic hyphomycete species.

Comparison of matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS) systems for the identification of moulds in the routine microbiology laboratory

OBJECTIVES

The purpose of this study was to compare the efficiency of mould identification of two matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS) systems - Vitek MS (VMS) and Microflex LT (MLT) - and the MSI application.

METHODS

Moulds were collected retrospectively and prospectively to display epidemiological diversity of a microbiology laboratory. All of them were identified via sequencing. Strains were then identified using the VMS v3.0, the MLT, and the MSI software applied on MLT spectra. Rates of correct identifications to the species, to the complex, and to the genus level were compared with the molecular reference standard.

RESULTS

A total of 102 isolates were collected. The rate of correct identification to the species level with the MLT was 42.2% (43/102) with a threshold of 1.7 (vs. 16.7% (17/102) with a threshold of 2.0, p < 0.05). The VMS performed better than the MLT with a threshold of 1.7 for species (49.0% (50/102), p 0.33) and complex level identifications (71.6% (73/102) vs. 54.9% (56/102), p < 0.05). However the highest performances were observed when the MLT spectra were analysed via the Mass Spectrometry Identification (MSI) software reaching 90.2% (92/102) of correct identification to the species, 92.2% (94/102) to the species complex and 94.1% (96/102) to the genus level.

CONCLUSIONS

The VMS performed better than the MLT for mould identification. However, it remains of utmost importance to expand commercial databases, as performances of the MLT highly improved when using the MSI software and its extended database, reaching far above the VMS system. Thus the VMS could benefit from the use of this online tool.

Ultra-High-Resolution Mass Spectrometry for Identification of Closely Related Dermatophytes with Different Clinical Predilections

In the present study, an innovative top-down liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the identification of clinically relevant fungi is tested using a model set of dermatophyte strains. The methodology characterizes intact proteins derived from Trichophyton species, which are used as parameters of differentiation. To test its resolving power compared to that of traditional Sanger sequencing and matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF), 24 strains of closely related dermatophytes, Trichophyton rubrum, T. violaceum, T. tonsurans, T. equinum, and T. interdigitale, were subjected to this new approach. Using MS/MS and different deconvolution algorithms, we identified hundreds of individual proteins, with a subpopulation of these used as strain- or species-specific markers. Three species, i.e., T. rubrum, T. violaceum, and T. interdigitale, were identified correctly down to the species level. Moreover, all isolates associated with these three species were identified correctly down to the strain level. In the T. tonsurans-equinum complex, eight out of 12 strains showed nearly identical proteomes, indicating an unresolved taxonomic conflict already apparent from previous phylogenetic data. In this case, it was determined with high probability that only a single species can be present. Our study successfully demonstrates applicability of the mass spectrometric approach to identify clinically relevant filamentous fungi. Here, we present the first proof-of-principle study employing the mentioned technology to differentiate microbial pathogens. The ability to differentiate fungi at the strain level sets the stage to improve patient outcomes, such as early detection of strains that carry resistance to antifungals.

Fast identification of dermatophytes by MALDI-TOF/MS using direct transfer of fungal cells on ground steel target plates

Dermatophytes cause human infections limited to keratinised tissues. We showed that the direct transfer method allows reliable identification of non-dermatophytes mould and yeast by MALDI-TOF/MS. We aimed at assessing whether the direct transfer method can be used for dermatophytes and whether an own mass spectra library would be superior to the Bruker library. We used the Bruker Biotyper to build a dermatophyte mass spectra library and assessed its performance by 1/testing a panel of mass spectrum produced with strains genotypically identified and, 2/comparing MALDI-TOF/MS identification to morphology-based methods. Identification of dermatophytes using the Bruker library is poor. Our library provided 97% concordance between ITS sequencing and MALDI-TOF/MS analysis with a panel of 1104 spectra corresponding to 276 strains. Direct transfer method using unpolished target plates allowed proper identification of 85% of dermatophytes clinical isolates most of which were common dermatophytes. A homemade dermatophyte MSP library is a prerequisite for accurate identification of species absent in the Bruker library but it also improves identification of species already listed in the database. The direct deposit method can be used to identify the most commonly found dermatophytes such as T. rubrum and T. interdigitale/mentagrophytes by MALDI-TOF/MS.

Multicenter Evaluation of the Vitek MS v3.0 System for the Identification of Filamentous Fungi

Invasive fungal infections are an important cause of morbidity and mortality affecting primarily immunocompromised patients. While fungal identification to the species level is critical to providing appropriate therapy, it can be slow and laborious and often relies on subjective morphological criteria. The use of matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry has the potential to speed up and improve the accuracy of identification. In this multicenter study, we evaluated the accuracy of the Vitek MS v3.0 system in identifying 1,601 clinical mold isolates compared to identification by DNA sequence analysis and supported by morphological and phenotypic testing. Among the 1,519 isolates representing organisms in the v3.0 database, 91% (n = 1,387) were correctly identified to the species level. An additional 27 isolates (2%) were correctly identified to the genus level. Fifteen isolates were incorrectly identified, due to either a single incorrect identification (n = 13) or multiple identifications from different genera (n = 2). In those cases, when a single identification was provided that was not correct, the misidentification was within the same genus. The Vitek MS v3.0 was unable to identify 91 (6%) isolates, despite repeat testing. These isolates were distributed among all the genera. When considering all isolates tested, even those that were not represented in the database, the Vitek MS v3.0 provided a single correct identification 98% of the time. These findings demonstrate that the Vitek MS v3.0 system is highly accurate for the identification of common molds encountered in the clinical mycology laboratory.

New method for the identification of arbuscular mycorrhizal fungi by proteomic-based biotyping of spores using MALDI-TOF-MS

Arbuscular mycorrhizal fungi (AMF, Glomeromycota) are mutualistic symbionts associated with majority of land plants. These fungi play an important role in plant growth, but their taxonomic identification remains a challenge for academic research, culture collections and inoculum producers who need to certify their products. Identification of these fungi was traditionally performed based on their spore morphology. DNA sequence data have successfully been used to study the evolutionary relationships of AMF, develop molecular identification tools and assess their diversity in the environment. However, these methods require considerable expertise and are not well-adapted for "routine" quality control of culture collections and inoculum production. Here, we show that Matrix-Assisted Laser Desorption Ionisation Time of Flight Mass Spectrometry proteomic-based biotyping is a highly efficient approach for AMF identification. Nineteen isolates belonging to fourteen species, seven genera and five families were clearly differentiated by MALDI biotyping at the species level, and intraspecific differentiation was achieved for the majority. AMF identification by MALDI biotyping could be highly useful, not only for research but also in agricultural and environmental applications. Fast, accurate and inexpensive molecular mass determination and the possibility of automation make MALDI-TOF-MS a real alternative to conventional morphological and molecular methods for AMF identification.

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.

Decision criteria for MALDI-TOF MS-based identification of filamentous fungi using commercial and in-house reference databases

BACKGROUND

Several Matrix-Assisted Laser Desorption/Ionization Time-of-Flight mass spectrometry protocols, which differ in identification criteria, have been developed for mold and dermatophyte identification. Currently, the most widely used approach is Bruker technology, although no consensus concerning the log(score) threshold has been established. Furthermore, it remains unknown how far increasing the number of spots to compare results might improve identification performance. In this study, we used in-house and Bruker reference databases as well as a panel of 422 isolates belonging to 126 species to test various thresholds. Ten distinct identification algorithms requiring one to four spots were tested.

RESULTS

Our findings indicate that optimal results were obtained by applying a decisional algorithm in which only the highest score of four spots was taken into account with a 1.7 log(score) threshold. Testing the entire panel enabled identification of 87.41% (in-house database) and 35.15% (Bruker database) of isolates, with a positive predictive value (PPV) of 1 at the genus level for both databases as well as 0.89 PPV (in-house database) and 0.72 PPV (Bruker database) at the species level. Applying the same rules to the isolates for which the species were represented by at least three strains in the database enabled identification of 92.1% (in-house database) and 46.6% (Bruker database) of isolates, with 1 PPV at the genus level for both databases as well as 0.95 PPV (in-house database) and 0.93 PPV (Bruker database) at the species level.

CONCLUSIONS

Depositing four spots per extract and lowering the threshold to 1.7, a threshold which is notably lower than that recommended for bacterial identification, decreased the number of unidentified specimens without altering the reliability of the accepted results. Nevertheless, regardless of the criteria used for mold and dermatophyte identification, commercial databases require optimization.

Identification of Molds by Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry

Although to a lesser extent than diagnostic bacteriology, matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has recently revolutionized the diagnostic mycology workflow. With regard to filamentous fungi (or molds), the precise recognition of pathogenic species is important for rapid diagnosis and appropriate treatment, especially for invasive diseases. This review summarizes the current experience with MALDI-TOF MS-based identification of common and uncommon mold species of Aspergillus, Fusarium, Mucorales, dimorphic fungi, and dermatophytes. This experience clearly shows that MALDI-TOF MS holds promise as a fast and accurate identification tool, particularly with common species or typical strains of filamentous fungi.

MALDI-TOF-Based Dermatophyte Identification

MALDI-TOF MS has become increasingly popular for microorganism identification in the routine laboratory. Compared with conventional morphology-based techniques, MALDI-TOF is relatively inexpensive (per-unit identification), involves a rapid result turnaround time and yields more accurate results without the need for highly qualified staff. However, this technology has been technically difficult to implement for filamentous fungi identification. Identification of dermatophytes, a type of filamentous fungi, remains particularly challenging, partly due to the lack of clear species definition for some taxa or within some species complexes. Review of the ten studies published between 2008 and 2015 shows that the accuracy of MALDI-TOF MS-based identification varied between 13.5 and 100 % for dermatophytes. This variability was partly due to inconsistencies concerning critical steps of the routine clinical laboratory process. Use of both a complete formic acid-acetonitrile protein extraction step and a manufacturer library supplemented with homemade reference spectra is essential for an accurate species identification. This technique is conversely unaffected by variations in other routine clinical laboratory conditions such as culture medium type, incubation time and type of mass spectrometry instrument. Provided that a reference spectra library is adequate for dermatophyte identification, MALDI-TOF MS identification is more economical and offers an accuracy comparable to that of DNA sequencing. The technique also represents an advantageous alternative to the protracted and labor-intensive dermatophyte identification via macroscopic and microscopic morphology in the routine clinical laboratory.

Matrix assisted laser desorption time of flight mass spectrometry (MALDI-TOF MS) in clinical microbiology

The microbiological management of patients with suspected bacterial infection includes the identification of the pathogen and the determination of the antibiotic susceptibility. These traditional approaches, based on the pure culture of the microorganism, require at least 36-48h. A new method, Matrix Assisted Laser Desorption Ionization Time of Flight Mass Spectrometry (MALDI-TOF MS), has been recently developed to profile bacterial proteins from whole cell extracts and obtain a bacterial fingerprint able to discriminate microorganisms from different genera and species. By whole cell-mass spectrometry, microbial identification can be achieved within minutes from cultured isolate, rather than traditional phenotypic or genotypic characterizations. From the year 2009 an explosion of applications of this technology has been observed with promising results. Several studies have been performed and showed that MALDI-TOF represents a reliable alternative method for rapid bacteria and fungi identification in clinical setting. A future area of expansion is represented by the application of MALDI-TOF technology to the antibiotic susceptibility test. In conclusion, the revision of the literature available up to date demonstrated that MALDI-TOF MS represents an innovative technology for the rapid and accurate identification of bacterial and fungal isolates in clinical settings. By an earlier microbiological diagnosis, MALDI-TOF MS contributes to a reduced mortality and hospitalization time of the patients and consequently has a significant impact on cost savings and public health.

Trichophyton erinacei in pet hedgehogs in Spain: Occurrence and revision of its taxonomic status

Hedgehogs have increased in popularity as pets in Spain but there are no data of infection rates of this exotic animal with dermatophytes in our country. During the period of 2008-2011 a total of 20 pet hedgehogs (19 African pygmy hedgehogs and 1 Egyptian long-eared hedgehog) suspected of having dermatophytoses were studied. This is the first survey of the occurrence of T. erinacei in household hedgehogs in Spain. The T. erinacei infection rate was 50% (9 out of 19 African pygmy hedgehogs, and the one Egyptian long-eared hedgehog surveyed). Morphological identification of the isolates was confirmed by molecular analysis. All the strains had the same ITS sequence and showed 100% sequence similarity to T. erinacei type strain CBS 511.73 (AB 105793). The Spanish isolates were confirmed as T. erinacei urease positive. On the basis of ITS sequences, T. erinacei is a species close to but separate from the taxa included in the A. benhamiae complex. Review of the current literature on DNA-based methods for identification of species included in this complex has highlighted the urgent need to reach a consensus in species circumscription and classification system accepted by all mycologists.

Diagnosis of Dermatophytosis Using Molecular Biology

Identification of fungi in dermatological samples using PCR is reliable and provides significantly improved results in comparison with cultures. It is possible to identify the infectious agent when negative results are obtained from cultures. In addition, identification of the infectious agent can be obtained in 1 day. Conventional and real-time PCR methods used for direct fungus identification in collected samples vary by DNA extraction methods, targeted DNA and primers, and the way of analysing the PCR products. The choice of a unique method in a laboratory is complicated because the results expected from skin and hair sample analysis are different from those expected in cases of onychomycosis. In skin and hair samples, one dermatophyte among about a dozen possible species has to be identified. In onychomycosis, the infectious agents are mainly Trichophyton rubrum and, to a lesser extent, Trichophyton interdigitale, but also moulds insensitive to oral treatments used for dermatophytes, which renders fungal identification mandatory. The benefits obtained with the use of PCR methods for routine analysis of dermatological samples have to be put in balance with the relative importance of getting a result in a short time, the price of molecular biology reagents and equipment, and especially the time spent conducting laboratory manipulations.

Evaluation of the Vitek MS Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry System for Identification of Clinically Relevant Filamentous Fungi

Invasive fungal infections have a high rate of morbidity and mortality, and accurate identification is necessary to guide appropriate antifungal therapy. With the increasing incidence of invasive disease attributed to filamentous fungi, rapid and accurate species-level identification of these pathogens is necessary. Traditional methods for identification of filamentous fungi can be slow and may lack resolution. Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has emerged as a rapid and accurate method for identification of bacteria and yeasts, but a paucity of data exists on the performance characteristics of this method for identification of filamentous fungi. The objective of our study was to evaluate the accuracy of the Vitek MS for mold identification. A total of 319 mold isolates representing 43 genera recovered from clinical specimens were evaluated. Of these isolates, 213 (66.8%) were correctly identified using the Vitek MS Knowledge Base, version 3.0 database. When a modified SARAMIS (Spectral Archive and Microbial Identification System) database was used to augment the version 3.0 Knowledge Base, 245 (76.8%) isolates were correctly identified. Unidentified isolates were subcultured for repeat testing; 71/319 (22.3%) remained unidentified. Of the unidentified isolates, 69 were not in the database. Only 3 (0.9%) isolates were misidentified by MALDI-TOF MS (including Aspergillus amoenus [n = 2] and Aspergillus calidoustus [n = 1]) although 10 (3.1%) of the original phenotypic identifications were not correct. In addition, this methodology was able to accurately identify 133/144 (93.6%) Aspergillus sp. isolates to the species level. MALDI-TOF MS has the potential to expedite mold identification, and misidentifications are rare.

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.

Evaluation of the Bruker Matrix-Assisted Laser Desorption-Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS) System for the Identification of Clinically Important Dermatophyte Species

Dermatophytes can invade the stratum corneum of the skin and other keratinized tissues and are responsible for a broad diversity of diseases of skin, nails and hair. Although the standard identification of dermatophytoses depends on macroscopic and microscopic characterization of the colonies grown on special media, there are a number of limitations owing to intraspecies morphological variability, atypical morphology or interspecies morphological similarity which entails improvement in the identification methods. Matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF MS) is a novel method which proved to be effective for rapid and reliable identification of dermatophytes grown in cultures when compared to conventional methods. We evaluated the performance of Bruker MALDI-TOF MS System (Bruker Daltonics, Germany) for identification of clinically relevant dermatophytes. In order to increase the identification capacity of the system, we created supplemental spectral database entries using ten reference dermatophyte strains (ten species in two genera). The utility of the generated database was then challenged using a total of 126 dermatophytes (115 clinical isolates and 11 additional reference strains). The results were evaluated by both manufacturer-recommended and lowered cutoff scores. MALDI-TOF MS provided correct identification in 122 (96.8 %) and 113 (89.7 %) of the isolates with the lowered scores and using the supplemented database, respectively, versus 65 (51.6 %) and 17 (13.5 %) correct identifications obtained by the unmodified database and recommended scores at the genus and species levels, respectively. Our results support the potential utility of MALDI-TOF MS as a routine tool for accurate and reliable identification of dermatophytes.