Rapid detection of dermatophytes and Candida albicans in onychomycosis specimens by an oligonucleotide array

PCR-Based Microarray Enhances Diagnosis of Culture-Negative Biopsied Tissue in Patients with Invasive Mold Infections: Real-World Experience in a Tertiary Medical Center

A fungal polymerase chain reaction (PCR) amplifies conserved genes across diverse species, combined with the subsequent hybridization of amplicons using a specific oligonucleotide microarray, allowing for the rapid detection of pathogens at the species level. However, the performance of microarrays in diagnosing invasive mold infections (IMI) from infected tissue samples is rarely reported. During the 4-year study period, all biopsied tissue samples from patients with a suspected IMI sent for microarray assays were analyzed. A partial segment of the internal transcribed spacer (ITS) region was amplified by nested PCR after DNA extraction. Amplicons were hybridized with specific probes for a variety of mold species using an in-house oligonucleotide microarray. A total of 80 clinical samples from 74 patients were tested. A diagnosis of an IMI was made in 10 patients (4 proven, 1 probable, 3 possible, 2 clinical suspicion). The PCR/microarray test was positive for three out of four proven IMIs, one probable IMI, and one out of three possible IMIs. Two patients with positive PCR/microarray findings were considered to have clinical suspicion of an IMI, and their responsible physicians initiated antifungal therapy despite the absence of supporting microbiological and histological evidence. Clinical diagnoses were categorized into non-IMI and IMI groups (including proven, probable, possible, and clinical suspicion). The sensitivity and specificity of the microarray in diagnosing the IMIs were 70% and 95.7%, respectively, while the sensitivity and specificity of the culture and histological findings were 10%/96.3% and 40.0%/100%, respectively. PCR-based methods provide supportive microbiological evidence when culture results are inconclusive. The combination of a microarray with fungal culture and histology promotes the precise diagnosis of IMIs in difficult-to-diagnose patients.

[Conventional and molecular diagnostics in onychomycosis-part 2 : Molecular identification of causative dermatophytes by polymerase chain reaction and sequence analysis of the internal transcribed spacer region of ribosomal DNA]

Dermatophyte identification using traditional methods such as optics-based direct fluorescence microscopy and culture is nowadays supplemented by molecular biological methods. The validity of dermatophyte DNA detection with direct uniplex-polymerase chain reaction-enzyme immunoassay (PCR-EIA) in nail samples was proven by sequence analysis of the ribosomal internal transcribed spacer (ITS) region. A total of 108 dermatophytes, isolated from patients with onychomycosis, were positive for Trichophyton rubrum (TR) and Trichophyton interdigitale (TI) in culture and/or uniplex-PCR-EIA. Conventional methods for dermatophyte identification were complemented by direct uniplex-PCR-EIA and sequence analysis of the ribosomal ITS region (18S rRNA, ITS1, 5.8S rRNA, ITS2, 28S rRNA). Of 108 patients (average age 62, median age 73), 56 showed cultural growth with 31 of them being identified as TR and 23 as TI. There was high agreement with the sequence analysis. Surprisingly, the pathogen of a single nail sample was identified as T. quinckeanum (formerly T. mentagrophytes sensu stricto), a rare zoophilic dermatophyte in Germany. A single TI strain turned out to be a misidentified T. tonsurans based on the sequence analysis. In all, 34 of the 52 specimens lacking cultural growth were detected by PCR as TR, and 18 specimens could be identified as TI. The results of dermatophyte identification of culture-negative nail samples were also in agreement with the results of sequence analysis. Molecular biological methods are well applicable, and they show high reliability for direct dermatophyte identification in nail samples without prior cultivation. Especially for nail samples without cultural growth, PCR-based dermatophyte identification was highly specific and sensitive.

Development and diagnostic evaluation of indirect enzyme linked immunosorbent assay for Epidermophyton floccosum infection in humans

BACKGROUND

Epidermophyton floccosum is an anthrophophilic dermatophyte widely distributed in the tropics and subtropics. It can invade keratinized tissues of humans and cause superficial mycoses called dermatophytosis (ringworm).

OBJECTIVE

The main objective of this study was to develop an in-house indirect enzyme-linked immunosorbent assay (ELISA) and to evaluate its performance for the immunological diagnosis of E. floccosum infection in humans.

METHODS

An in-house indirect ELISA was developed using partially purified E. floccosum antigens, pre immunized rabbit serum as negative control, immunized rabbit polyclonal antibodies as positive control, enzyme labeled goat anti rabbit antibodies and goat anti human antibodies. A total of 50 serum samples from E. floccosum infected patients as confirmed by direct microscopy and culture and 30 samples from humans without history of dermatophyte infection that served as controls were used to evaluate the performance of an in-house indirect ELISA developed in this study. Analytical and diagnostic performance characteristics were determined to evaluate its diagnostic value.

RESULTS

The diagnostic sensitivity, specificity, positive and negative predictive values of E. floccosum indirect ELISA were 90.00 %, 83.33 %, 90.83 %, 83.83 % respectively. The performance of indirect ELISA assay was compared with gold standard diagnostic tests such as KOH hydrolysis test and fungal culture. The correlation coefficients of E. floccosum indirect ELISA with KOH hydrolysis and fungal culture method were 0.612** and 0.826** (P < 0.01) respectively indicating significant correlation between these tests.

CONCLUSION

This revealed the great potentiality of E. floccosum indirect ELISA in early, specific and precise detection of E. floccosum infection in humans.

Development of Indirect ELISA and its evaluation in Comparison with KOH hydrolysis and Fungal culture for the immuno diagnosis of Trichophyton rubrum and Trichophyton mentagrophytes infection in Humans

Trichophyton is a keratinophilic fungus that can invade keratinized tissues of humans and cause superficial mycoses called dermatophytosis. The objective of this study was to develop and evaluate indirect ELISA in comparison with gold standard methods such as direct microscopic examination of KOH mounts and fungal culture for the diagnosis of Trichophyton infection in humans. The present investigation reports the production and partial purification of T. rubrum mycelial antigens and production of specific polyclonal antibodies. It also reports the development and optimization of indirect ELISA and evaluation of its potential in comparison with gold standard methods for the diagnosis of Trichophyton infection in humans. The diagnostic sensitivity and specificity of Trichophyton indirect ELISA was 93.75% and 93.33 % respectively. The positive and negative predictive values were high as well, found to be 93.75% and 90.00% respectively indicating usefulness of the assay. In all comparisons, the correlation coefficient (r) value was >0.5 indicating strong correlation between KOH hydrolysis test, fungal culture method and indirect ELISA. A significant correlation coefficient of 0.856 (P < 0.0001) was obtained between indirect ELISA and fungal culture method. This shows a good agreement between fungal culture method and indirect ELISA. The present study clearly shows diagnostic performance of Trichophyton indirect ELISA developed in this study is efficient as fungal culture method for the diagnosis of Trichophyton infection in humans.

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.

Updates in Laboratory Diagnostics for Invasive Fungal Infections

Appropriate diagnosis of invasive fungal infections (IFIs) is critical due to the high rates of morbidity and mortality, as well as the substantial economic burden, associated with the management of these diseases. The recognition of IFI and differentiation from other infections with similar clinical presentations can be challenging, which can lead to diagnostic error that not only has an impact on individual patient health outcomes but also on antimicrobial drug usage and the growing threat of antimicrobial resistance in bacteria. Therefore, there is a significant need for improved stewardship related to diagnostic testing for and treatment of IFIs. The purpose of this review is to highlight recent advances related to current fungal diagnostics, as well as explore some of the most innovative technology that has emerged with the potential to shift the paradigm of clinical mycology. In general, this review will discuss research related to enhanced fungal culture utilization and identification techniques, expanded applications of fungal antigen testing, and recently developed molecular assays and other novel nonculture fungal diagnostic approaches. Specifically, the application of mass spectrometry, novel glycobiomarker detection, and detection of fungal-specific volatile organic compounds will be reviewed, along with other key updates, to provide the reader with an updated review that extends beyond the basics of IFI laboratory diagnostics. Where appropriate, the reader will be directed to more comprehensive reviews of certain aspects of clinical mycology laboratory testing to provide a broader context for the critical consideration of these updates.

Nonculture Diagnostics in Fungal Disease

Fungal diagnostics that utilize antibody, antigen or nucleic acid detection offer several advantages that supplement traditional culture-based methods. As a group, nonculture assays can help identify patients with invasive fungal infection (IFI) sooner than is possible with culture, are often more sensitive, and can be used to guide early interventions. Challenges associated with these techniques include the possibility for contamination or cross-reactivity as well as the potential for false negative tests. This review summarized the test characteristics and clinical utility of nonculture-based laboratory methods.

Antidermatophytic Activity of Ethanolic Extract from Croton tiglium

Dermatophytosis, which is caused mainly by genera of Trichophyton, Epidermophyton, and Microsporum, is a frequent dermatological problem in tropical and subtropical countries. Investigations were carried out in this study to evaluate the antidermatophytic activity of the stems, leaves, and seeds of Croton tiglium, one of the traditional medicine plants indigenous to Asia. Ethanolic extracts of the stems, leaves, and seeds of C. tiglium were prepared by cold soak or heat reflux methods. The antidermatophytic activities of the extracts were evaluated by disc diffusion and microdilution susceptibility assays against Trichophyton mentagrophytes, T. rubrum, and Epidermophyton floccosum. The active components in the extracts were analyzed and identified by GC-MS. All ethanolic extracts of C. tiglium showed some antifungal activities against the three dermatophytes. The ethanolic stem extract had the greatest inhibitory activities against T. mentagrophytes and E. floccosum with MICs at 0.16 mg/mL and had a lower activity against T. rubrum (MIC: 0.31 mg/mL). Oleic acid and hexadecanoic acid were found to be the major constituents in the stem extract that demonstrated strong antidermatophytic activities. The ethanolic extracts of stem or seed of C. tiglium exhibit strong antidermatophytic activities and, thus, could be considered for application on treating skin fungal infections after appropriate processing.