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

A Current Diagnostic and Therapeutic Challenge: Tinea Capitis

Tinea capitis is a dermatophyte scalp infection with a marked prevalence among the pediatric population. However, in the last few years, its epidemiology has changed due to increasing population migration worldwide. Host-specific and environmental factors contribute to the pathogenesis of tinea capitis. Clinically, tinea capitis may present as a subtle hair loss accompanied by scalp scaling, alopecia with scaly patches, or alopecia with black dots. A more severe form of tinea capitis is represented by kerion celsi, which clinically presents as a tender plaque covered by pustules and crusts. If left untreated, this dermatophytic infection may resolve with permanent scarring and alopecia. The pathological changes found in tinea capitis are reflected by a spectrum of clinical changes. Zoophilic infections typically prompt an extensive inflammatory reaction, while anthropophilic dermatophytoses often lack inflammation and result in more persistent lesions. Tinea capitis typically requires systemic antifungal therapy. Griseofulvin, terbinafine, itraconazole, and fluconazole are the main antifungal agents used. Currently, the duration of antifungal therapy varies based on the clinical presentation and type of dermatophyte involved. Through the reported cases and literature review, we aim to emphasize the importance of the early recognition of atypical variants of tinea capitis in immunocompetent children for the prompt initiation of systemic antifungal therapy, minimizing the need for prolonged treatment. Additionally, we emphasize the importance of regular laboratory testing during systemic antifungal therapy, particularly liver enzyme tests, to prevent adverse events, especially in cases requiring long-term treatment.

Mini-Review: The Diagnostic Methods of Tinea Capitis

Tinea capitis is a widespread superficial fungal infection that affects children predominately. Microscopic examination and fungal culture are the conventional gold standards for diagnosis, but they are insensitive and time-consuming. In recent years, new diagnostic methods have been developed to facilitate the diagnosis and identification of causative pathogens. Trichoscopy examination showed high sensitivity and specificity for diagnosing tinea capitis with the characteristic signs of comma hairs, corkscrew hairs, bar code-like hairs and zigzag hairs. Reflectance confocal microscopy has also been used in the rapid diagnosis of tinea capitis in several studies. Molecular assays such as polymerase chain reaction and matrix-assisted desorption/ionization time to flight mass spectrometry are extensively utilized for rapid and accurate identification of the pathogens. Early diagnosis and treatment can aid in disease control and scarring reduction.

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.

Performance of Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry for Identification of Scedosporium, Acremonium-Like, Scopulariopsis, and Microascus Species

Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has emerged as a powerful microorganism identification tool. Research on MALDI-TOF MS identification of rare filamentous fungi is still lacking. This study aimed to evaluate the performance of MALDI-TOF MS in the identification of Scedosporium, Acremonium-like, Scopulariopsis, and Microascus species. Sabouraud broth cultivation and formic acid/acetonitrile protein extraction were used for MALDI-TOF MS identification by a Bruker Biotyper system. An in-house database containing 29 isolates of Scedosporium, Acremonium-like, Scopulariopsis, and Microascus spp. was constructed. A total of 52 clinical isolates were identified using the Bruker Filamentous Fungi Library v1.0 (FFL v1.0) alone, and Filamentous Fungi Library v1.0 plus the in-house library, respectively. The mass spectrum profile (MSP) dendrograms of the 28 Scedosporium isolates, 26 Acremonium-like isolates, and 27 Scopulariopsis and Microascus isolates were constructed by MALDI Biotyper OC 4.0 software, respectively. The correct species identification rate significantly improved when using the combined databases compared with that when using FFL v1.0 alone (Scedosporium spp., 75% versus 0%; Acremonium-like spp., 100% versus 0%; Scopulariopsis and Microascus spp., 100% versus 62.5%). The MSP dendrograms differentiated Acremonium-like species, Scopulariopsis and Microascus species clearly, but cannot distinguish species in the Scedosporium apiospermum complex. In conclusion, with an expanded database, MALDI-TOF MS is an effective tool for the identification of Scedosporium, Acremonium-like, Scopulariopsis, and Microascus species.

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.