Distinct characteristics of Scytalidium dimidiatum and non-dermatophyte onychomycosis as compared with dermatophyte onychomycosis

Onychomycosis due to Fusarium species in different continents, literature review on diagnosis and treatment

Fusarium species are an emerging cause of onychomycosis, and the number of cases has dramatically increased in recent decades worldwide. This review presents an overview of the onychomycosis cases caused by Fusarium species and diagnosis and treatment that have been reported in the literature. The most common causative agent of onychomycosis is F. solani species complex, which accounts for 11.68% of the cases of Fusarium onychomycosis, followed by the F. oxysporum species complex (164 out of 1669), which is accounted for 9.83% of the total. F. fujikuroi species complex (42 out of 1669) and F. dimerum species complex (7 out of 1669) are responsible for 2.52% and 0.42 cases, respectively. Fusarium nail infections were reported in patients aged range 1-98, accounting for 5.55% (1669 out of 30082) of all cases. Asia has the highest species diversity of Fusarium onychomycosis (31.51%). South America accounts for 21.09%, and the most common causative agent is F. solani (19.32%), followed by F. oxysporum species complex (15.63%). Europe accounts for 4.90% of cases caused by F. oxysporum, followed by F. solani. Africa accounts for 23.87% of the cases due to the F. solani species complex, followed by F. oxysporum and F. fujikuroi. Distal and lateral subungual onychomycosis was the most common clinical symptom accounting for 58.7% (135 out of 230) of the cases. Data analysis relieved that terbinafine and itraconazole are active treatments for Fusarium onychomycosis. For a definitive diagnosis, combining of direct examination, culture and sequencing of the elongation factor of translation 1α are recommended. Accurate identification of the causative agents of onychomycosis due to Fusarium species and antifungal susceptibility testing is essential in patient management.

Developing diagnostic criteria to differentiate fungal foot infections caused by Neoscytalidium dimidiatum and dermatophytes

Background

The predisposing factors and clinical presentations of fungal foot infections caused by non-dermatophytes and dermatophytes are challenging to differentiate. Definite diagnoses of non-dermatophyte infections at first visits facilitate their treatment.

Objectives

This study aimed to develop diagnostic criteria to differentiate fungal foot infections caused by Neoscytalidium dimidiatum and dermatophytes.

Methods

Diagnostic prediction research based on a retrospective, observational, cross-sectional study. The reviewed patients were aged ≥18 and underwent a mycological examination for fungal foot infections. A fungal culture at the initial visit was the gold standard for determining causative organisms.

Results

Analyses were carried out on the data from 371 patients. N. dimidiatum accounted for 184 (49.6%) infections, and dermatophytes caused the remaining 187 (50.4%) cases. Five significant predefined predictors were used to develop the diagnostic criteria and score. They were immunocompetence status, no family history of fungal infections, the absence of pruritus, the absence of other concurrent fungal skin infections, and agricultural work. The lower score cutoff was <8 (sensitivity 97.8% and specificity 25.7%). The higher cutoff was >11 (sensitivity 83.7% and specificity 57.8%). The score showed an area under the receiver operating characteristic curve of 0.755 and was well calibrated.

Conclusions

The criteria and score show promise for clinical use, with acceptable discriminative performance and good calibration. They will help physicians differentiate the causative organisms in patients with fungal foot infections at the first visit, enabling the determination of appropriate antifungal treatment.

Single-Point Nail Sampling to Diagnose Onychomycosis Caused by Non-Dermatophyte Molds: Utility of Polymerase Chain Reaction (PCR) and Histopathology

The three most commonly used methods for diagnosing non-dermatophyte mold (NDM) onychomycosis are culture, polymerase chain reaction (PCR), and histopathology. Toenail samples from 512 patients (1 sample/patient) with suspected onychomycosis were examined using all three diagnostic tests. A statistically significant association was found between PCR and histopathology results, as well as between fungal culture and histopathology results. All PCR-positive and culture-positive dermatophyte samples were confirmed by histopathology. However, 15/116 (12.9%) of culture-positive NDM samples had negative histopathology results, while all PCR-positive NDM samples were confirmed by histopathology. The overall rate of dermatophyte detection was higher using PCR compared to culture (38.9% vs. 11.7%); the lower rate of NDM detection by PCR (11.7% vs. 38.9%) could be attributed to the restriction of the assay design to seven pre-selected targets. When repeat sampling in the clinic is not possible, a combination of NDM detection by PCR and positive histopathology of hyphae may be a proxy for NDM infection, particularly where the NDM occurs without a concomitant dermatophyte. There was a high degree of correlation between negative PCR and negative histopathology. A negative PCR result with negative histopathology findings may be a reliable proxy for the diagnosis of non-fungal dystrophy.

Cutaneous Fungal Infections Caused by Dermatophytes and Non-Dermatophytes: An Updated Comprehensive Review of Epidemiology, Clinical Presentations, and Diagnostic Testing

Cutaneous fungal infection of the skin and nails poses a significant global public health challenge. Dermatophyte infection, mainly caused by Trichophyton spp., is the primary pathogenic agent responsible for skin, hair, and nail infections worldwide. The epidemiology of these infections varies depending on the geographic location and specific population. However, epidemiological pattern changes have occurred over the past decade. The widespread availability of antimicrobials has led to an increased risk of promoting resistant strains through inappropriate treatment. The escalating prevalence of resistant Trichophyton spp. infections in the past decade has raised serious healthcare concerns on a global scale. Non-dermatophyte infections, on the other hand, present even greater challenges in terms of treatment due to the high failure rate of antifungal therapy. These organisms primarily target the nails, feet, and hands. The diagnosis of cutaneous fungal infections relies on clinical presentation, laboratory investigations, and other ancillary tools available in an outpatient care setting. This review aims to present an updated and comprehensive analysis of the epidemiology, clinical manifestations, and diagnostic testing methods for cutaneous fungal infections caused by dermatophytes and non-dermatophytes. An accurate diagnosis is crucial for effective management and minimizing the risk of antifungal resistance.

Prognostic factors for mycological cure in patients with onychomycosis caused by Neoscytalidium dimidiatum: A retrospective cohort study

BACKGROUND

The prognostic factors for cure have been derived from cases of dermatophyte onychomycosis. However, there are limited studies in non-dermatophyte onychomycosis. Neoscytalidium dimidiatum is the common causative agents of non-dermatophyte onychomycosis which has proven to be recalcitrant to treatment.

OBJECTIVE

This retrospective cohort study investigated mycological cure and prognostic factors in Neoscytalidium onychomycosis patients.

METHODS

Patients aged 18 or older with newly diagnosed Neoscytalidium onychomycosis were enrolled. All patients were treated and followed up for at least 1 year. Mycological cure was analysed with Cox proportional hazard regression. The hazard ratios (HRs) of previously reported potential prognostic factors were included in univariable and multivariable stratified Cox regression analyses.

RESULTS

From total 198 patients, mycological cure was achieved in 108 (54.6%) patients with a median of 490 (± SD 62.2) days. The poor prognostic factors for mycological cure were age ≥ 70 years (HR, 0.63; 95% CI, 0.41-0.97; p = .034); nail thickness ≥2 mm (HR, 0.20; 95% CI, 0.11-0.35; p < .001); and peripheral vascular disease (HR, 0.46; 95% CI, 0.28-0.77; p = .003). Combination therapy was associated with achieving a mycological cure (HR, 2.55; 95% CI, 1.49-4.38; p < .001).

CONCLUSIONS

Approximately half of the patients with onychomycosis caused by Neoscytalidium dimidiatum achieved a mycological cure, with a median time to cure exceeding 1 year. Combined topical and systemic antifungal treatments yield a higher chance of mycological cure than monotherapies. Advanced age, nail thickness and peripheral vascular disease are obstacle factors to cure.

Effectiveness and safety of topical amphotericin B in 30% dimethyl sulfoxide cream versus 30% dimethyl sulfoxide cream for nondermatophyte onychomycosis treatment: A pilot study

BACKGROUND

Although topical amphotericin B cream is effective for the treatment of nondermatophyte mold onychomycosis in vitro, studies of its effectiveness and safety in vivo are limited.

OBJECTIVES

We studied the effectiveness and safety of topical 0.3% amphotericin B in 30% dimethyl sulfoxide cream (amphotericin B cream) in nondermatophyte mold onychomycosis using the vehicle cream 30% dimethyl sulfoxide cream as control.

METHODS

This randomized controlled study was conducted between January 2019 and November 2020. Patients diagnosed with nondermatophyte mold onychomycosis were randomly divided into two groups of ten patients each: one treated with amphotericin B cream and the other with the vehicle cream. Clinical and mycological cure as well as safety were evaluated.

RESULTS

Ten patients each treated with amphotericin B cream and the vehicle cream were included in the study, but only nine patients in the vehicle cream group were available for follow up. All the 19 evaluable patients had distal lateral subungual onychomycosis and the great toenails were affected in 18 (94.7%) of these. Mycological cure was achieved in 8 (80%) patients treated with amphotericin B cream and in 4 (44.4%) patients using the control (vehicle) cream. Clinical cure was achieved in 7 (70%) patients treated with amphotericin B cream, but only in 2 (22.2%) patients on the control cream. No adverse events were observed.

LIMITATIONS

The small sample size and the fact that PCR fungal identification that provides accurate identification of fungal species was not performed are limitations of our study.

CONCLUSION

Topical amphotericin B cream was both very effective and safe in the treatment nondermatophyte mold onychomycosis. The control (vehicle) cream containing 30% dimethyl sulfoxide also demonstrated some antifungal activity.

Epidemiological analysis of nail aspergillosis and non-dermatophyte moulds. Criteria for the involvement of Aspergillus in 102 cases of onychomycosis at Montpellier University Hospital, France (1991-2019)

BACKGROUND

Moulds are often wrongly considered contaminants, not very sensitive to conventional antifungal treatments, but they may cause ungual hyphomycosis, particularly Aspergillus. Due to the lack of precise diagnostic criteria, their real impact is underestimated.

OBJECTIVES

Retrospective descriptive analysis of all ungual hyphomycosis cases diagnosed at Montpellier Hospital from 1991 to 2019 to: (i) determine the incidence of onychomycosis by pseudo-dermatophytes and moulds; (ii) perform an epidemiological analysis of nail aspergillosis; and (iii) provide simple criteria for mould involvement in onychopathy.

PATIENTS/METHODS

Data concerning 4053 patients were collected: age, sex, onychomycosis location, direct examination results, species(s) identified and fungal co-infections. Moreover, clinical data of patients with nail aspergillosis were analysed to identify potential contributing factors, and the classical criteria for mould involvement in onychopathy were critically reviewed.

RESULTS

A pseudo-dermatophyte or a mould was involved in nail colonisation in 17.25% of patients (men/women ratio: 0.70; mean age: 53.1 years). The identified hyphomycetes belonged mainly to the genera Fusarium (45.68%), Scopulariopsis (30.23%) and Aspergillus (16.94%). Analysis of the clinical reports of 102 patients with ungual aspergillosis (men/women ratio: 0.67; mean age: 56.3 years) identified cardiovascular (43.9%), endocrine (25.8%), cancer (19.7%) and skin (18.2%) diseases as contributing factors.

CONCLUSIONS

The adoption of simple and reliable criteria (ie, characteristic filaments on direct microscopic examination after periodic acid-Schiff staining, growth at seeding points in culture) allows determining the formal involvement of a mould in chronic onychopathies and avoiding possible side effects and costs of empirical or inappropriate and repetitive treatments.

Onychomycosis in older adults: The age and associated factors affecting the complete cure rate

BACKGROUND

Limited studies exist on the factors associated with a complete cure of onychomycosis in older adults.

OBJECTIVES

To determine the age and factors associated with a complete cure among older adults diagnosed with toenail onychomycosis.

METHODS

A retrospective cohort study was conducted of 95 older adult patients (aged ≥ 60 years) diagnosed with toenail onychomycosis between January 2016 and December 2017. Demographic data, mycological findings, treatments and durations to a complete cure were reviewed.

RESULTS

The complete cure rates of the patients aged < 70 years and ≥70 years were 67.4% and 44.9%, respectively (P = 0.027). Patients aged ≥ 70 years were significantly higher in male gender, had higher history of smoking, peripheral arterial disease, impaired renal function, antihypertensive drug and amorolfine nail lacquer usage, and polypharmacy. A multivariate analysis revealed that being aged ≥70 years and having a nail thickness >2 mm were associated with failure to achieve a complete cure. The median times to a complete cure for older adults aged <70 years and ≥70 years were 20 months and 47 months, respectively (P = 0.007).

CONCLUSIONS

An age ≥ 70 years was related to a lower cure rate and delays in achieving a complete cure. A nail thickness > 2 mm was a poor prognostic factor for a complete cure. Moreover, very old adults were more likely to suffer side effects arising from the use of systemic antifungal medications.

Genotyping and In Vitro Antifungal Susceptibility Profile of Neoscytalidium Species Isolates from Respiratory Tract

The fungus genus Neoscytalidium is mainly distributed in (sub) tropical regions of the world and has been essentially considered as a phytopathogen. There are however several reports of human infection caused by Neoscytalidium spp. through direct or indirect contact with contaminated plants or soil. Reliable and accurate identification to species level is critical for implementing proper therapeutic strategies. In the present study we investigated the genotypes and in vitro antifungal susceptibility patterns of Neoscytalidium species identified from respiratory tracts of patients with various underlying diseases. The identity and diversity of the isolates were done using PCR and sequencing of five different loci (the ITS region, D1/D2 domains of 28S rRNA gene, and part of the beta tubulin, elongation factor 1α and chitin synthase genes). The in-vitro antifungal susceptibility was also performed using the Clinical and Laboratory Standards Institute (CLSI) M38-Ed3-2017 guidelines. Overall, 13 isolates were identified as Neoscytalidium species (eight N. dimidiatum and five N. novaehollandiae). Two sequence types (STs) were identified by the alignment of 1846 combined base pairs among 13 clinical isolates. All isolates classified as N. dimidiatum were clustered in ST6 (61.5%) and those of N. novaehollandiae were in ST7 (38.5%). Luliconazole was the most active antifungal in vitro against species. This is the first report of N. novaehollandiae isolation from respiratory tracts samples. Further study from other regions of the world with a larger set of clinical specimens is required to provide additional insight into diversity of Neoscytalidium species.

Predisposing factors, clinical features and treatment outcomes of Fusarium onychomycosis and comparison of its characteristics with Neoscytalidium onychomycosis

BACKGROUND

Fusarium spp. are common organisms causing onychomycosis. Research on the clinical presentations and treatment of this condition is limited.

OBJECTIVE

This study evaluated the demographic data, clinical characteristics, and treatment outcomes of Fusarium onychomycosis.

METHODS

A retrospective study was conducted at Siriraj Hospital, Thailand. Patients with onychomycosis, at least 2 repeated positive mycological cultures for Fusarium spp., and a photo at diagnosis (January 2014-December 2019) were included. Demographic data and clinical characteristics of Fusarium onychomycosis were analyzed and compared with those of Neoscytalidium onychomycosis, the other common nondermatophytes onychomycosis in tropical countries.

RESULTS

Seventeen patients with twenty-four nails were analyzed. Fusarium onychomycosis was significantly related to a history of pedicure (p = 0.04). Predominant lateral involvements of subungual hyperkeratosis onychomycosis, but without concurrent foot infections, were significantly found in Fusarium onychomycosis (p < 0.001 for each). Among the treatments, urea was 80% effective. Topical amphotericin B was 75% effective. Both amorolfine 5% nail lacquer and long-pulsed 1064-nm neodymium:yttrium-aluminum-garnet laser were 66.7% effective. Lastly a combination of long-pulsed 1064-nm neodymium:yttrium-aluminum-garnet laser and amorolfine 5% nail lacquer was 50% effective.

CONCLUSIONS

Important predisposing factors and clinical manifestations of Fusarium onychomycosis were a history of pedicure and predominant lateral-nail involvement, but no concomitant fungal foot infections. Topical treatment (urea cream, amphotericin B, or amorolfine nail lacquer) showed excellent outcomes.

Onychomycosis caused by the environmental mold Neoscytalidium dimidiatum in Colombia, and in vitro antifungal susceptibility evaluation

Neoscytalidium dimidiatum is a plant pathogen, but can also cause onychomycosis. We compared clinical and epidemiological data of cases of onychomycosis caused by N. dimidiatum and Trichophyton rubrum. We also evaluated the in vitro antifungal susceptibility of N. dimidiatum clinical isolates. It was not possible to establish any statistical differences between groups, except the place of residence and the number of affected nails. The results suggest that onychomycosis caused by N. dimidiatum is clinically similar to that caused by T. rubrum; besides, N. dimidiatum has been shown to have low sensitivity to itraconazole, but high to terbinafine.

LAY SUMMARY

Cases of onychomycosis caused by Neoscytalidium dimidiatum were studied and compared to cases of onychomycosis caused by T. rubrum. The individuals affected were adults, and the clinical characteristics were not different between groups; accordingly, mycological diagnosis is mandatory.

Non-dermatophyte Mould Onychomycosis in Japan

The incidence of non-dermatophyte mould onychomycosis has been increasing worldwide for the past several decades, but it is not well recognized in Japan. Recent molecular techniques and phylogenetic analyses contributed to the identification of uncommon and emerging species. We came across 13 (0.5%) cases of non-dermatophyte onychomycosis among a total of 2,591 onychomycosis cases in 106,703 outpatients during the past 5 years (January 2015-December 2019). The cases included 5 patients with Aspergillus species, 4 patients with Fusarium species, and one patient each with Scopulariopsis brevicaulis and Botryosphaeria dothidea, respectively. Botryosphaeria dothidea is closely related phylogenetically to Neoscytalidium dimidiatum. In Japan, at the time of writing this report, there are 26 reported cases of ungual aspergillosis and 18 cases of hyalohyphomycosis caused by Fusarium species. We summarize these cases and report the symptoms and mycological features.

Nail Disease for the Primary Care Provider

Nail disorders are a common presenting complaint for both the primary care physician and the dermatologist. Nail diagnoses are broad in scope and include infectious, inflammatory, and neoplastic conditions. Onychomycosis is an especially common nail condition, and treatment should always be preceded by appropriate fungal studies for confirmation of diagnosis. Inflammatory conditions of the nail unit can mimic onychomycosis, and a dermatologist can assist with diagnosis and treatment recommendations. Likewise, subungual tumors often require biopsy, and should be evaluated by a dermatologist who is experienced in nail evaluation and treatment.