Development of a novel polymerase chain reaction-enzyme-linked immunosorbent assay for the diagnosis ofTrichophyton rubrumonychomycosis

[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.

Novel Discoveries and Clinical Advancements for Treating Onychomycosis: A Mechanistic Insight

Onychomycosis continues to be the most challenging disease condition for pharmaceutical scientists to develop an effective drug delivery system. Treatment challenges lie in incomplete cure and high relapse rate. Present compilation provides cumulative information on pathophysiology, diagnostic techniques, and conventional treatment strategies to manage onychomycosis. Novel technologies developed for successful delivery of antifungal molecules are also discussed in brief. Multidirectional information offered by this article also unlocks the panoramic view of leading patented technologies and clinical trials. The obtained clinical landscape recommends the use of advanced technology driven approaches, as a promising way-out for treatment of onychomycosis. Collectively, present review warrants the application of novel technologies for the successful management of onychomycosis. This review will assist readers to envision a better understanding about the technologies available for combating onychomycosis. We also trust that these contributions address and certainly will encourage the design and development of nanocarriers-based delivery vehicles for effective management of onychomycosis.

Rapid and Accurate Diagnosis of Dermatophyte Infections Using the DendrisCHIP® Technology

Dermatophytosis is a superficial fungal infection with an ever-increasing number of patients. Culture-based mycology remains the most commonly used diagnosis, but it takes around four weeks to identify the causative agent. Therefore, routine clinical laboratories need rapid, high throughput, and accurate species-specific analytical methods for diagnosis and therapeutic management. Based on these requirements, we investigated the feasibility of DendrisCHIP® technology as an innovative molecular diagnostic method for the identification of a subset of 13 pathogens potentially responsible for dermatophytosis infections in clinical samples. This technology is based on DNA microarray, which potentially enables the detection and discrimination of several germs in a single sample. A major originality of DendrisCHIP® technology is the use of a decision algorithm for probability presence or absence of pathogens based on machine learning methods. In this study, the diagnosis of dermatophyte infection was carried out on more than 284 isolates by conventional microbial culture and DendrisCHIP®DP, which correspond to the DendrisCHIP® carrying oligoprobes of the targeted pathogens implicated in dermatophytosis. While convergence ranging from 75 to 86% depending on the sampling procedure was obtained with both methods, the DendrisCHIP®DP proved to identify more isolates with pathogens that escaped the culture method. These results were confirmed at 86% by a third method, which was either a specific RT-PCR or genome sequencing. In addition, diagnostic results with DendrisCHIP®DP can be obtained within a day. This faster and more accurate identification of fungal pathogens with DendrisCHIP®DP enables the clinician to quickly and successfully implement appropriate antifungal treatment to prevent the spread and elimination of dermatophyte infection. Taken together, these results demonstrate that this technology is a very promising method for routine diagnosis of dermatophytosis.

Evaluation of different DNA extraction methods based on steel-bullet beating for molecular diagnosis of onychomycosis

BACKGROUND

Considering increased trends toward molecular methods for detection/identification of fungi causing onychomycosis, the aim of this study is comparison three DNA extraction methods based on steel-bullet beating to extract DNA from nail.

METHODS

Ex -vivo onychomycosis model was developed using bovine hoof with Candida albicans and Aspergillus flavus. For two models, total DNA was extracted using the three different methods. In method 1, the extraction and purification were performed by steel-bullet beating and phenol chloroform protocol, respectively. In method 2, a freezing step were applied before beating. The purification step in method 3 was carried out using a commercial kit, although DNA extraction was done similarly to method 1 in that approach. To evaluate the efficacy of each method, the extracted genomic DNA was amplified with Polymerase Chain Reaction (PCR) using Internal Transcribed Spacer (ITS) regions. Moreover, 50 nail samples were evaluated for onychomycosis using direct microscopy examination as well as PCR in order to evaluate the diagnostic efficiency of the optimal DNA extraction method.

RESULTS

Regarding the desirable quality of the extracted DNA, cost effectiveness, and simplicity, method 1 could be used to extract DNA effectively. Additionally, the obtained data showed that PCR had a higher detection rate of fungal agents in the nail samples than direct microscopic examination.

CONCLUSIONS

This study demonstrated that the mechanical disruption of the cell wall by steel-bullet beating is a useful and practical method to improve the quantity and quality of fungal DNA thorough the extraction process.

DNA-Chip-basierte Diagnose der Onychomykose und Tinea pedis

HINTERGRUND UND ZIELE

Onychomykose (OM) und Tinea pedis (TP) sind häufige Pilzinfektionen der Haut. Aktuell basiert die Diagnose vornehmlich auf mikroskopischem Direktnachweis und/oder Kultur. Beide Methoden haben jedoch eine geringe bis mäßige Sensitivität und benötigen teilweise mehrere Wochen, bis endgültige Laborergebnisse vorliegen. Um die Diagnose kutaner Pilzinfektionen zu verbessern, wurden PCR-basierte Methoden entwickelt. Hier haben wir hier die Sensitivität und Spezifität einer Chip-basierten Multiplex-PCR mit mikroskopischen Direktnachweis und verglichen.

PATIENTEN UND METHODIK

In einer monozentrischen, prospektiven Studie wurden bei Patienten mit Verdacht auf OM (n  =  67) oder TP (n  =  73) Schuppenpräparate entnommen und mittels mikroskopischem Direktnachweis, Kultur und DNA-Chip-Technologie der Erregernachweis durchgeführt. In einem weiteren Ansatz wurde überprüft, ob Abstriche als Alternative zur Entnahme eines Schuppenpräparates verwendet werden können. Hierfür wurden 24 weitere OM/TP-Patienten rekrutiert und die Ergebnisse der DNA-Chip-Technologie aus Abstrichen mit denen aus den Schuppenpräparaten verglichen.

ERGEBNISSE

Im Vergleich aller Methoden hatte die DNA-Chip-Technologie die höchste Sensitivität, eine Kombination von DNA-Chip-Technologie mit mikroskopischem Direktnachweis erhöhte dies weiter. Ergebnisse dieser kombinierten Labordiagnostik sind innerhalb von 24 Stunden verfügbar. Der Vergleich der Probenentnahmetechniken (Abstrich beziehungsweise Schuppenpräparat) zeigte vergleichbare Ergebnisse.

SCHLUSSFOLGERUNGEN

Die molekulare Diagnostik (mittels DNA-Chip-Technologie) hat eine hohe Sensitivität für die OM- und TP-Diagnostik, insbesondere in Kombination mit dem mikroskopischen Direktnachweis.

Tiefe Trichophytie bei Tinea corporis

Mykosen sind weit verbreitete Infektionskrankheiten, die durch unterschiedliche Erreger hervorgerufen werden und sich im klinischen Alltag unterschiedlich präsentieren können. Je nach Manifestationsort und Erreger kommen entsprechend unterschiedliche Behandlungsoptionen in Betracht. Wir stellen im Folgenden einen Patienten mit einer ungewöhnlichen tiefen Trichophytie bei Tinea corporis und Onychomykose vor. Der Patient wurde topisch und systemisch mit Terbinafin behandelt.

Diese Kasuistik ist insofern erwähnenswert, da es sich um eine durch zwei unterschiedliche Erreger hervorgerufene Mykose handelt, die möglicherweise durch den vorbestehenden Diabetes begünstigt wurde und eine besondere therapeutische Herausforderung darstellt.

Identification of the causative dermatophyte of tinea capitis in children attending Mbarara Regional Referral Hospital in Uganda by PCR-ELISA and comparison with conventional mycological diagnostic methods

Tinea capitis is a dermatophyte infection common among prepubertal children in sub-Saharan Africa and mainly caused by Trichophyton and Microsporum species. Accurate identification is challenging as conventional methods like culture and microscopy are slow and mostly based on morphological characteristics, which make them less sensitive and specific. Modern molecular methods, like polymerase chain reaction (PCR) assays, are gaining acceptance and are quick as well as accurate. The aim of this study was to investigate the clinical patterns of tinea capitis and to accurately identify the most common causative dermatophytes affecting the scalps of children aged 1 to 16 years attending the Skin Clinic at Mbarara University of Science and Technology (MUST), Mbarara, Uganda, East Africa, using both conventional mycological methods and PCR-ELISA for detection of dermatophyte DNA. One hundred fifteen clinical samples from children from Western Uganda attending the MUST Skin Clinic with a clinical diagnosis of tinea capitis were analyzed. T. violaceum was identified as the most common causative agent, followed by M. audouinii, T. soudanense, and T. rubrum. The early identification of the causative agent of tinea capitis is a prerequisite for the effective management of the disease, the identification of probable source and the prevention of spreading. Children with tinea capitis in Western Uganda should be treated by systemic therapy rather than topical preparations to ensure high cure rates as the most common causative dermatophytes T. violaceum exhibits an endothrix rather than ectothrix invasion of the hair follicle.

Comparison of fungal fluorescent staining and ITS rDNA PCR-based sequencing with conventional methods for the diagnosis of onychomycosis

BACKGROUND

The current gold standard for diagnosing onychomycosis is direct microscopic examination and culturing. Fungal culture is a time-consuming procedure, while direct microscopy of potassium hydroxide (KOH) mounts suffers from low sensitivity. More rapid and sensitive methods for the diagnosis of onychomycosis are in high demand.

OBJECTIVE

To establish an effective method for the diagnosis of onychomycosis by assessing the efficacies of fungal fluorescent staining and internal transcribed spacer (ITS) ribosomal DNA (rDNA) polymerase chain reaction (PCR)-based sequencing.

METHODS

A total of 204 clinical specimens from patients with suspected onychomycosis were analysed. The gold standard for a true positive sample was positive by KOH, culturing or both methods. All specimens were also tested by fungal fluorescent staining and ITS rDNA PCR-based sequencing. We compared the detection, sensitivity and specificity for these two methods with conventional methods.

RESULTS

In total, 126 (62%) and 102 (50%) were detected by fluorescent staining and PCR-based sequencing, respectively. According to the conventional diagnostic standard, the sensitivity of fluorescent staining and PCR-based sequencing was 97% and 78%, respectively, and specificities of 89% and 90%, respectively. Use of fluorescence enhanced the sensitivity of direct examination by 12% compared with KOH. PCR-based sequencing increased the sensitivity by 6% compared with culturing.

CONCLUSIONS

Fluorescence microscopy has a higher sensitivity for the detection of fungi in nail specimens compared with KOH and can be used as a rapid screening tool. PCR-based sequencing was faster and more sensitive compared with culture and when used in conjunction with fluorescence microscopy resulted in higher efficiency.

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.

Development a diagnostic pan-dermatophyte TaqMan probe real-time PCR assay based on beta tubulin gene

Early differentiation of dermatophytosis from other cutaneous mycoses is essential to avoid inaccurate therapy. DNA-based techniques including real-time PCR have increasingly been considered for detection of fungal elements in clinical specimens. In this study, after partial sequence analysis of beta tubulin (BT2) gene in 13 common and rare pathogenic dermatophyte species, a pan-dermatophyte primer and probe set was designed in a TaqMan probe-based PCR format. The sensitivity and specificity of the system was tested with 22 reference strains of dermatophytes, 234 positive clinical specimens, 32 DNA samples extracted from normal nails, several fungi other than dermatophytes and human DNAs. Analytical detection limit of the designed PCR on serially diluted DNAs of prepared recombinant plasmid indicated that only five molecules per sample are the minimum number for reliable detection by the assay. A total of 226 out of 234 (96.5%) DNAs extracted from clinical samples, but none of the 32 nail samples, from healthy volunteers were positive in PCR. The real-time PCR targeted beta tubulin gene established in this study could be a sensitive diagnostic tool which is significantly faster than the conventional culture method and should be useful in the clinical settings, in large-scale epidemiological studies and in clinical trials of antifungal therapy.

Mycology - an update part 2: dermatomycoses: clinical picture and diagnostics

Most fungal infections of the skin are caused by dermatophytes, both in Germany and globally. Tinea pedis is the most frequent fungal infection in Western industrial countries. Tinea pedis frequently leads to tinea unguium, while in the elderly, both may then spread causing tinea corporis. A variety of body sites may be affected, including tinea glutealis, tinea faciei and tinea capitis. The latter rarely occurs in adults, but is the most frequent fungal infection in childhood. Following antifungal treatment of tinea unguium and also tinea capitis a dermatophytid or hyperergic reaction to dermatophyte antigens may occur. Yeast infections affect the mucous membranes both of the gastro-intestinal system and the genital tract as candidiasis mostly due to Candida albicans. Cutaneous candidiasis affects predominantely the intertriginous regions such as groins and the inframammary area, but also the intertriginous space of fingers and toes. In contrast, pityriasis versicolor is a superficial epidermal fungal infection primarily on the the trunk. Mold infections are rare in dermatology; they play a role nearly exclusively in nondermatophyte-mold (NDM) onychomycosis. The diagnosis of dermatomycoses comprises the microscopic detection of fungi using the potassium hydroxide preparation or alternatively the fluorescence optical Blankophor preparation together with culture. The histological fungal detection with PAS staining possesses a high sensitivity, and it should play a more important role in particular for diagnosis of onychomycosis. Molecular biological methods, based on the amplification of fungal DNA with use of specific primers for the distinct causative agents are on the rise. With PCR, such as dermatophyte-PCR-ELISA, fungi can be detected directly in clinical material in a highly specific and sensitive manner without prior culture. Today, molecular methods, such as Matrix Assisted Laser Desorption/Ionization Time-Of-Flight Mass Spectrometry (MALDI TOF MS) as culture confirmation assay, complete the conventional mycological diagnostics.

Molecular diagnosis of onychomycosis

Onychomycosis is a frequent cause of nail infections due to dermatophytes. Molds and yeast may also be responsible of these pathologies. Antifungal treatments are frequently given without a mycological diagnosis, partly because of the requisite time for obtaining the biological results. The mycological diagnosis requires a direct microscopic examination and a culture in order to accurately identify the fungal genus and species. Nevertheless, this conventional diagnosis is often time consuming due to the delay of fungal cultures and presents disadvantages that make it not sufficient enough to give a precise and confident response to the clinicians. Therefore additional tests have been developed to help distinguish onychomycosis from other nail disorders. Among them, molecular biology techniques offer modern and rapid tools to improve traditional microbiological diagnosis. In this review, we first present the conventional diagnosis methods for onychomycosis and then we describe the main molecular biology tools and the currently available commercial kits that allow a rapid detection of the pathology.