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

[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.

Diagnostic yield of calcofluor white in the identification of Candida albicans in oral squamous cell carcinoma

Background

Although oral cancer is multifactorial in origin only few had evaluated the diagnostic parameters for candidal infection in oral squamous cell carcinoma (OSCC).

Aims

To compare and assess the accuracy of Calcofluor White (CFW) to that of conventional staining methods to identify the presence of candidal infection in OSCC.

Methods

Archival collections of 43 OSCC were retrieved for this investigation. Standard staining protocol was followed for the index test (CFW) and reference standard (Periodic Acid Schiff). Two examiners were blinded for either one of the staining techniques. Diagnostic test evaluation and Kappa statistic was calculated using MedCalc software.

Results

The study comprised 37 males, six females, and their mean age at the time of presentation was 51 (range 23 to 75 years). The sensitivity and specificity of CFW was 75.8% (CI 57.7 to 88.9%) and 10.0% (CI 0.2 to 44.5%). While the positive predictive and negative predictive values were 63.1% (CI - 50.6-74.0%) and 67.0% (CI - 49.2-81.0%).

Conclusion

Our results show minimal agreement with PAS with a Kappa score of 0.148 (95% CI = 0.39 to 0.09). Overall detection rate was similar for both the index test and reference standard although there was considerable number of intermediate test results. Sensitivity of CFW was comparable to that of earlier studies but specificity was low and the degree of concordance was 60.4%. Although CFW staining can come with high false positive they are a useful test for ruling out candida infection when the test result is negative.

Comparison of Fungal Fluorescent Staining and ITS rDNA PCR-based Sequencing with Conventional Methods for Diagnosis of Onychomycosis

Accurate identification of fungal causes for onychomycosis is essential for proper treatment. Presently available laboratory methods show unreliable sensitivity; so there is a requirement for innovative detection techniques. The aim for this work was to assess the efficiencies of fluorescent staining and internal transcribed spacer (ITS) ribosomal DNA (rDNA) polymerase chain reaction (PCR)-based sequencing in comparison to conventional techniques for diagnosis of onychomycosis. Nail specimens obtained from 100 patients with clinically- diagnosed onychomycosis were analyzed. Nail scrapings or clippings were subjected to direct microscopic examination by KOH mount, culture by using Sabouraud’s dextrose agar and histopathological examination with periodic-acid Schiff (PAS). Collected specimens were subsequently examined by fluorescent staining and PCR-based sequencing (30 specimens only) to compare the feasibility, sensitivity and diagnostic accuracy for these two methods. The most frequently isolated fungi were yeasts (39/76: 51.3%), dermatophytes (24/76; 31.6%) and non-dermatophyte molds (NDMs) (13/76; 17.1%). Mixed mycotic infections were recovered from 6% of the collected nail specimens. The positive detection rates were significantly different between KOH examinations (52%), nail plate histology (55%), fungal culture (70%) and fluorescent staining (80%). Considering fungal culture as the gold standard, the most sensitive technique was PCR (100%) followed by fluorescent staining (89%), PAS staining (69%) while the least sensitive technique was KOH mount (53%). Fluorescence staining can be used as a rapid and high-yield technique for identification of fungi in the specimens. PCR-based sequencing was highly sensitive and faster compared to culture. Whenever possible, it enables species identification with higher adequacy.

Diagnosing Onychomycosis: What’s New?

An overview of the long-established methods of diagnosing onychomycosis (potassium hydroxide testing, fungal culture, and histopathological examination) is provided followed by an outline of other diagnostic methods currently in use or under development. These methods generally use one of two diagnostic techniques: visual identification of infection (fungal elements or onychomycosis signs) or organism identification (typing of fungal genus/species). Visual diagnosis (dermoscopy, optical coherence tomography, confocal microscopy, UV fluorescence excitation) provides clinical evidence of infection, but may be limited by lack of organism information when treatment decisions are needed. The organism identification methods (lateral flow techniques, polymerase chain reaction, MALDI-TOF mass spectroscopy and Raman spectroscopy) seek to provide faster and more reliable identification than standard fungal culture methods. Additionally, artificial intelligence methods are being applied to assist with visual identification, with good success. Despite being considered the ‘gold standard’ for diagnosis, clinicians are generally well aware that the established methods have many limitations for diagnosis. The new techniques seek to augment established methods, but also have advantages and disadvantages relative to their diagnostic use. It remains to be seen which of the newer methods will become more widely used for diagnosis of onychomycosis. Clinicians need to be aware of the limitations of diagnostic utility calculations as well, and look beyond the numbers to assess which techniques will provide the best options for patient assessment and management.

Real-life applicability of the Euroarray Dermatomycosis Kit in the diagnosis of onychomycosis

BACKGROUND

Traditionally, KOH microscopy and fungal culture are the two preferred tests as gold standard for diagnosis of onychomycosis. Recently, other diagnostic methods have been developed to improve the microbiological diagnosis. The EUROArray dermatomycosis kit is a PCR-based microarray test system for the detection and direct identification of species that are most frequently involved in skin and nail infections.

OBJECTIVES

Our primary aim was to evaluate the real-life applicability of the EUROArray dermatomycosis kit in the diagnosis of onychomycoses. In addition, we compared the etiology of onychomycoses found in our patients with those described in the literature.

PATIENTS/METHODS

We prospectively studied consecutive 100 patients with suspected onychomycoses. Samples of suspect toenails were taken as part of routine medical management. Nail specimens were evaluated by means of 3 diagnostic methods: KOH preparation, culture and EUROArray dermatomycosis kit.

RESULTS

Onychomycosis was diagnosed in 47/100 patients who proved positive on at least one reference diagnostic test and in 49/100 patients who proved positive on PCR. The combination of microscopy and PCR had better sensitivity than microscopy (p=0.0397), fungal culture (p=0.0061) and PCR alone (p=0 .0117). Molds were more frequently positive in culture than in PCR (p=0.033). Dermatophytes proved positive more frequent than molds and yeasts in both culture and PCR; in particular, Trichophyton interdigitale was the most frequent pathogen.

CONCLUSIONS

In conclusion, introducing EUROArray dermatomycosis kit into the diagnostic algorithm of onychomycosis increases the sensitivity of direct microscopy and yields more rapid results than culture.

Combined laser and ozone therapy for onychomycosis in an in vitro and ex vivo model

In order to develop a fast combined method for onychomycosis treatment using an in vitro and an ex vivo models, a combination of two dual-diode lasers at 405 nm and 639 nm wavelengths, in a continuous manner, together with different ozone concentrations (until 80 ppm), was used for performing the experiments on fungal strains growing on PDA agar medium or on pig’s hooves samples. In the in vitro model experiments, with 30 min combined treatment, all species are inhibited at 40 ppm ozone concentration, except S. brevicaulis, which didn’t show an inhibition in comparison with only ozone treatment. In the ex vivo model experiments, with the same duration and ozone concentration, A. chrysogenum and E. floccosum showed total inhibition; T. mentagrophytes and T. rubrum showed a 75% growth inhibition; M. canis showed a delay in sporulation; and S. brevicaulis and A. terreus did not show growth inhibition. This combined laser and ozone treatment may be developed as a fast therapy for human onychomycosis, as a potential alternative to the use of antifungal drugs with potential side effects and long duration treatments.

Rapid detection of fungi from blood samples of patients with candidemia using modified calcofluor white stain

We reported a modified CFW assay for rapid detection of fungi in blood samples and evaluated its efficacy in vivo and in vitro. The positive rate, sensitivity, and negative predictive values of the modified CFW method were all significantly higher than those of traditional fungal culture and KOH methods.

PAS stain based histological classification and severity grading of toenail onychomycosis

Onychomycosis is a common world-wide health issue. Accurate detection is essential for treatment. Multiple studies have shown that PAS-stain based histological visualization of fungal elements is superior to either direct microscopy with 20% potassium hydroxide, or fungal culture. However, PAS stain based histological classification and severity grading of onychomycosis are lacking in the literature. Here we reported a fungal detection rate of 47.87% based on an analysis of 13,805 toenails processed for H&E and PAS stains over a three year period. Based on the analysis of fungal density, distribution and infiltrating depth level in 858 PAS-positive toenails, we created a novel PAS stain based histological classification system to classify onychomycosis as occult onychomycosis (OO), focal or diffuse subungual onychomycosis (FSO or DSO), focal or diffuse plate onychomycosis (FPO or DPO), focal or diffuse subungual and plate onychomycosis (FSPO or DSPO) and superficial onychomycosis (SO). The severities of OO, FSO and FPO were graded as mild, DSO and DPO as moderate, FSPO and DSPO as severe infections, which revealed that more than 75% PAS positive toenails were severe infections. Evaluation of 97 paired toenails biopsied pre- and post-treatment from 47 patients demonstrated that the severity of infection was significantly reduced from severe to mild and moderate levels. These data indicate that the current histological classification evaluates not only the severity of the fungal infection but also the response to treatment. We further propose a guideline for treatment of onychomycosis based on the histological classification and severity.

Diagnostic value of fluorescein-labeled chitinase staining in formalin-fixed and paraffin-embedded tissues of fungal disease

Common histopathologic techniques are used to diagnose fungal infections, but the diagnostic identification of mycoses in tissue specimens is often difficult, particularly when fungi rarely occur in a specimen. The aim of this study was to evaluate the application of fluorescein-labeled chitinase staining to formalin-fixed and paraffin-embedded (FFPE) tissues. We studied 79 archival FFPE tissues from patients diagnosed with fungal disease, including 38 cases of sporotrichosis and 41 cases of other fungal infections. The tissue sections were subjected to periodic acid-Schiff (PAS) staining, Gomori's methenamine silver (GMS) staining, and fluorescein-labeled chitinase staining to detect fungal elements. Culture- and/or hematoxylin-eosin-positive samples were used to estimate the diagnostic sensitivity of each staining method, with the results showing that PAS, GMS, and fluorescein-labeled chitinase staining had sensitivities of 50.6, 70.9, and 68.4%, respectively. The three staining results were the same for all fungal infections except for sporotrichosis and chromoblastomycosis. Fluorescein-labeled chitinase staining exhibited high sensitivity in cases of sporotrichosis and poor performance in detecting muriform cells of chromoblastomycosis. On the whole, the sensitivity of fluorescein-labeled chitinase staining was greater than that of PAS and similar to that of GMS staining. Therefore, the results of our study suggest that fluorescein-labeled chitinase staining is a potentially useful diagnostic tool in the diagnosis of fungal infections.

Fusarium onychomycoses in Switzerland-A mycological and histopathological study

Onychomycoses in temperate climates are most commonly due to dermatophytes, particularly Trichophyton rubrum. Non-dermatophyte nail infections are much less frequent, and their diagnosis requires a careful and repeated search for a potential dermatophyte that may have been overgrown in culture. A series of histological slides of suspected onychomycoses with uncommon fungal morphology prompted us to search for non-dermatophytic moulds causing dermatophytosis-like nail infections. Thirty cases were identified by culture as F solani, F oxysporum, F dimerum or F spp, and two more were only diagnosed histopathologically. None of these patients was immunocompromised. Treatment was mostly unsuccessful with terbinafine whereas itraconazole showed a moderately better treatment result; in all cases, a topical ciclopirox nail varnish in a hydroxychitosan base was added.

Application of fungal fluorescent staining in oral candidiasis: diagnostic analysis of 228 specimens

Background

Several conventional methods, including fungal culture and periodic acid-Schiff (PAS) reagent staining, have been used to diagnose oral candidiasis. The aim of this study was to evaluate the efficacy of a novel method, fungal fluorescent staining, in relation to conventional protocols in the diagnosis of oral candidiasis.

Methods

We collected 106 oral swabs and 122 oral biopsy tissues from patients highly suspected with oral candidiasis. We applied fungal culture and periodic acid-Schiff reagent staining as the gold standard diagnostic tools. The efficacy of these methods in determining the presence of Candida was compared with that of fluorescent staining.

Results

In the majority of specimens subjected to fluorescent staining, fungal organisms were distinguished by blue fluorescence surrounding their tubular or annular shapes. The sensitivity, specificity, Youden index, positive predictive value and negative predictive value of the fluorescent staining method were 82.7, 93.5, 76.7, 96.8 and 69.1% in oral swabs and 90.0, 92.9, 82.9, 96.0 and 82.9% in oral biopsy tissues, respectively.

Conclusions

Fungal fluorescent staining represents a rapid method for detection of Candida, supporting its potential utility as an effective early diagnostic tool for oral candidiasis.

Liquid chromatography-tandem mass spectrometry is effective for analysis of ergosterol in fungal-infected nails

BACKGROUND

Identification of onychomycosis is mainly based on clinical diagnosis with auxiliary diagnostic methods such as potassium hydroxide (KOH) microscopy, periodic acid-Schiff staining or fungal culture. However, each method is limited by its sensitivity and specificity.

AIM

To develop a new test method using the common fungal end product, ergosterol, and investigate if it can be used as a new diagnostic tool.

METHODS

We collected consecutive data from 20 participants with nail problems. Following clinical diagnosis, samples were taken for KOH microscopy and for mass spectrometry (MS) to check for the presence of ergosterol.

RESULTS

Of the 20 cases collected, 7 were positive for fungal infection by MS. Four of these were already suspected to have onychomycosis, whereas one of the remaining three subjects was presumed to have dry nail and the other two to have onycholysis. The MS test seemed to be better at detecting combinations of nail conditions. Conversely, of the five patients clinically diagnosed as having onychomycosis, four had a positive MS result, whereas the fifth had negative results on both KOH and MS. Two other participants had a positive KOH test and were also found to have positive MS results.

CONCLUSION

Detection of the presence of ergosterol by MS seems to be a useful tool for confirming onychomycosis. However, further studies are needed to verify the sensitivity and specificity of this MS method.

Case Study of Onychomycosis Patients Treated with 1,064-nm Nd:YAG Laser

Onychomycosis is the most frequent nail disease, with an estimated prevalence of 2-8%. Current treatment strategies include the use of oral and topical antifungals, despite low cure rates following these treatments. The objectives of this study were to assess the therapeutic response of patients with onychomycosis to 1,064-nm Nd:YAG laser treatment, the clinical evaluation method available for this therapy, and the possible side effects of this treatment. Twenty patients with onychomycosis underwent laser therapy. A total of 34 nails with onychomycosis were assessed according to the Onychomycosis Severity Index (OSI). This index generates scores that classify onychomycosis as mild, moderate, or severe. The OSI was determined before treatment and after a mean follow-up period of 8 months. The comparison between the initial and the final OSI for all 34 nails treated with laser therapy showed a significant difference; however, a low association was shown between these variables. A general reduction in the area of involvement and in the OSI numerical scores was observed. These data show a trend toward improvement in onychomycosis treated with 1,064-nm Nd:YAG laser. The OSI allowed an adequate clinical assessment of the response to laser therapy. Laser treatment did not cause marked discomfort in most patients, indicating that laser is a well-tolerated procedure.