Evaluation of DermaGenius® resistance real-time polymerase chain reaction for rapid detection of terbinafine-resistant Trichophyton species

Antifungal resistance in dermatophytes - review of the epidemiology, diagnostic challenges and treatment strategies for managing Trichophyton indotineae infections

INTRODUCTION

There is an increasing number of reports of Trichophyton indotineae infections. This species is usually poorly responsive to terbinafine.

AREAS COVERED

A literature search was conducted in May 2024. T.indotineae infections detected outside the Indian subcontinent are generally associated with international travel. Reports of local spread are mounting.As a newly identified dermatophyte species closely related to the T. mentagrophytes complex with limited genetic and phenotypic differences, there is an unmet need to develop molecular diagnosis for T. indotineae. Terbinafine has become less effective as a first-line agent attributed to mutations in the squalene epoxidase gene (Leu393Phe, Phe397Leu). Alternative therapies include itraconazole for a longer time-period or a higher dose (200 mg/day or higher). Generally, fluconazole and griseofulvin are not effective. In some cases, especially when the area of involvement is relatively small, topical non-allylamine antifungals may be an option either as monotherapy or in combination with oral therapy. In instances when the patient relapses after apparent clinical cure then itraconazole may be considered. Good antifungal stewardship should be considered at all times.

EXPERT OPINION

When both terbinafine and itraconazole are ineffective, options include off-label triazoles (voriconazole and posaconazole). We present four patients responding to these newer triazoles.

Potential emergence of terbinafine resistance by squalene epoxidase gene mutations: An 18-month cohort study of onychomycosis patients in the United States

BACKGROUND

There is a concerning rise in antifungal-resistant dermatophytosis globally, with resistance to terbinafine conferred by point mutations in the squalene epoxidase (SQLE) gene.

OBJECTIVES

Report changes in the prevalence and profile of SQLE mutations in onychomycosis patients in the United States.

METHODS

A longitudinal cohort study of toenail samples was collected from suspected onychomycosis patients over an 18-month period from 2022 to 2023. Samples were submitted from across the United States and subjected to multiplex real-time polymerase chain reactions for dermatophyte detection, with further screening of SQLE mutations at four known hotspots (393Leu, 397Phe, 415Phe and 440His).

RESULTS

A total of 62,056 samples were submitted (mean age: 57.5 years; female: 60.4%). Dermatophytes were detected in 38.5% of samples, primarily Trichophyton rubrum complex (83.6%) and T. mentagrophytes complex (10.7%). A survey of SQLE mutations was carried out in 22,610 dermatophyte samples; there was a significant increase in the prevalence of SQLE mutations between the first quarter of 2022 and the second quarter of 2023 (29.0 to 61.9 per 1000 persons). The Phe397Leu substitution was the predominant mutation; Phe415Ser and His440Tyr have also emerged which were previously reported as minor mutations in skin samples. The temporal change in mutation rates can be primarily attributed to the Phe415Ser substitution. Samples from elderly patients (>70 years) are more likely to be infected with the T. mentagrophytes complex including strains harbouring the Phe415Ser substitution.

CONCLUSION

The prevalence of SQLE mutations among onychomycosis patients with Trichophyton infections may be underestimated. Older individuals may have a higher risk.

Molecular Diagnostics for Invasive Fungal Diseases: Current and Future Approaches

Invasive fungal diseases (IFDs) comprise a growing healthcare burden, especially given the expanding population of immunocompromised hosts. Early diagnosis of IFDs is required to optimise therapy with antifungals, especially in the setting of rising rates of antifungal resistance. Molecular techniques including nucleic acid amplification tests and whole genome sequencing have potential to offer utility in overcoming limitations with traditional phenotypic testing. However, standardisation of methodology and interpretations of these assays is an ongoing undertaking. The utility of targeted Aspergillus detection has been well-defined, with progress in investigations into the role of targeted assays for Candida, Pneumocystis, Cryptococcus, the Mucorales and endemic mycoses. Likewise, whilst broad-range polymerase chain reaction assays have been in use for some time, pathology stewardship and optimising diagnostic yield is a continuing exercise. As costs decrease, there is also now increased access and experience with whole genome sequencing, including metagenomic sequencing, which offers unparalleled resolution especially in the investigations of potential outbreaks. However, their role in routine diagnostic use remains uncommon and standardisation of techniques and workflow are required for wider implementation.

Expert Panel Review of Skin and Hair Dermatophytoses in an Era of Antifungal Resistance

Dermatophytoses are fungal infections of the skin, hair, and nails that affect approximately 25% of the global population. Occlusive clothing, living in a hot humid environment, poor hygiene, proximity to animals, and crowded living conditions are important risk factors. Dermatophyte infections are named for the anatomic area they infect, and include tinea corporis, cruris, capitis, barbae, faciei, pedis, and manuum. Tinea incognito describes steroid-modified tinea. In some patients, especially those who are immunosuppressed or who have a history of corticosteroid use, dermatophyte infections may spread to involve extensive skin areas, and, in rare cases, may extend to the dermis and hair follicle. Over the past decade, dermatophytoses cases not responding to standard of care therapy have been increasingly reported. These cases are especially prevalent in the Indian subcontinent, and Trichophyton indotineae has been identified as the causative species, generating concern regarding resistance to available antifungal therapies. Antifungal-resistant dermatophyte infections have been recently recognized in the United States. Antifungal resistance is now a global health concern. When feasible, mycological confirmation before starting treatment is considered best practice. To curb antifungal-resistant infections, it is necessary for physicians to maintain a high index of suspicion for resistant dermatophyte infections coupled with antifungal stewardship efforts. Furthermore, by forging partnerships with federal agencies, state and local public health agencies, professional societies, and academic institutions, dermatologists can lead efforts to prevent the spread of antifungal-resistant dermatophytes.

Development of an agar-based screening method for terbinafine, itraconazole, and amorolfine susceptibility testing of Trichophyton spp

Resistance in dermatophytes is an emerging global public health issue. We, therefore, developed an agar-based method for screening Trichophyton spp. susceptibility to terbinafine (TRB), itraconazole (ITC), and amorolfine (AMF) and validated it using molecularly characterized isolates. Α total of 40 Trichophyton spp. isolates, 28 TRB wild type (WT) (13 T. rubrum, 10 T. mentagrophytes, 5 T. interdigitale) and 12 TRB non-WT (7 T. rubrum, 5 T. indotineae) with different alterations in the squalene epoxidase (SQLE) gene, were used. The optimal test conditions (inoculum and drug concentrations, incubation time, and temperature) and stability over time were evaluated. The method was then applied for 86 WT Trichophyton spp. clinical isolates (68 T. rubrum, 7 T. interdigitale, 6 T. tonsurans, 5 T. mentagrophytes) and 4 non-WT T. indotineae. Optimal growth of drug-free controls was observed using an inoculum of 20 µL 0.5 McFarland after 5-7 days of incubation at 30°C. The optimal concentrations that prevented the growth of WT isolates were 0.016 mg/L of TRB, 1 mg/L of ITC, and 0.25 mg/L of AMF, whereas 0.125 mg/L of TRB was used for the detection of Trichophyton strong SQLE mutants (MIC ≥0.25 mg/L). The agar plates were stable up to 4 months. Inter-observer and inter-experimental agreement were 100%, and the method successfully detected TRB non-WT Trichophyton spp. strains showing 100% agreement with the reference EUCAST methodology. An agar-based method was developed for screening Trichophyton spp. in order to detect TRB non-WT weak and strong mutant isolates facilitating their detection in non-expert routine diagnostic laboratories.

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.

Dermatophyte Infections Worldwide: Increase in Incidence and Associated Antifungal Resistance

The increase in incidence of superficial fungal infections combined with the emergence of antifungal resistance represents both a global health challenge and a considerable economic burden. Recently, dermatophytes, the main culprit causing superficial fungal infections, have started to exhibit antifungal resistance. This can be observed in some of the most common species such as Trichophyton rubrum and Trichophyton mentagrophytes. Importantly, the new subspecies, known as Trichophyton indotineae, has been reported to show high resistance to terbinafine, a first-line treatment for dermatophyte infections. Compounding these issues is the realization that diagnosing the causative infectious agents requires using molecular analysis that goes beyond the conventional macroscopic and microscopic methods. These findings emphasize the importance of conducting antifungal susceptibility testing to select the appropriate antifungal necessary for successful treatment. Implementing these changes may improve clinical practices that combat resistant dermatophyte infections.

Majocchi's granuloma-A multicenter retrospective cohort study

Background

Majocchi's granuloma (MG) is an uncommon deep fungal folliculitis predominantly caused by dermatophytes. Given the rarity of this condition, available data regarding predisposing comorbidities/risk factors, clinical characteristics, offending microbiologic pathogens, diagnostics, pathologic findings, and treatment approaches has been inferred from historical cases.

Objectives

To review our institutional experience with MG.

Methods

We retrospectively analyzed a multicenter cohort of adult patients diagnosed with MG between 1992 and 2022.

Results

We analyzed 147 patients with MG, 105 of which were male with a median age of 55.6 years. Immunosuppressant and topical corticosteroid use were common prior to development of MG. Dermatologic lesions and their sites of involvement did not differ based on the immune status of patients. Trichophyton rubrum was the most common causative pathogen of MG, in addition to other dermatophytes. Treatment duration for all prescribed agents was median 31.5 days with oral terbinafine being the most frequently utilized agent. Clinical resolution was achieved in 96.6% of cases.

Limitations

Retrospective, nonrandomized study.

Conclusions

Although rare and clinically variable in presentation, diagnosis of MG often requires histopathologic confirmation to subsequently direct prolonged treatment with systemic antifungal therapy for mycological cure.

A Terbinafine Sensitive Trichophyton indotineae Strain in Italy: The First Clinical Case of tinea corporis and onychomycosis

Trichophyton indotineae is an emerging dermatophyte species that plays a relevant role in human healthcare. It has been associated with severe chronic skin infections and a high level of terbinafine resistance. T. indotineae is endemic to India, Iran, and Iraq but several cases have been reported in Europe, recently. In this manuscript, the authors report the first clinical description of a tinea corporis and onychomycosis due to T. indotineae. The patient was a 42-year-old female from India that has lived in Umbria (Central Italy) for the last two years. Firstly, a dermatological examination suggested dermatophytosis: mycology isolation from cultures and macro- and microscopical features identified the colonies as belonging to the T. mentagrophytes/T. interdigitale species complex. Subsequently, ITS1/ITS4 end-point PCR and Sanger sequencing identified the strain as T. indotineae. Lastly, a DermaGenius® Resistance Multiplex real-time PCR assay was carried out, targeting the mutations in the SQLE gene to establish terbinafine resistance or susceptibility of the strain. The melting curve observed was compatible with wild-type positive control, identifying the strain as T. indotineae terbinafine-sensitive. An oral terbinafine treatment was associated with a topical ciclopirox nail solution, resulting in remission in its clinical manifestation. On 3 July 2023, the local Prevention Service notified the case to the Ministry of Health that then reported the information at national and international levels.

Therapeutic treatment strategies for the management of onychomycosis: a patent perspective

INTRODUCTION

Onychomycosis, a multifactorial fungal infection of the nails, shows a global prevalence of about 5.5% and is responsible for 50% of all nail infections. To develop effective management strategies, it is necessary to understand the etiology, pathophysiology, and risk factors of onychomycosis. Oral route of drug delivery is one of the routes utilized to deliver anti-fungal agents, but, has its own limitations like longer duration of treatment, increased adverse effects, and potential for drug interaction. The ungual route has received greater attention due to its localized, non- invasive action and improved patient compliance.

AREAS COVERED

This review comprehensively discusses conventional onychomycosis therapies and patented novel drug delivery systems for the management of onychomycosis including chemical permeation enhancers, non-particulate drug delivery systems, penetration enhancing devices etc., Databases such as PubMed, ResearchGate, and Google Patents were searched by using the keywords onychomycosis and trans-ungual drug delivery.

EXPERT OPINION

Enormous research has been conducted and is still ongoing to find the best possible novel drug delivery system for onychomycosis management. Approaches like incorporation of herbal constituents in nano-formulations, inkjet printing, laser devices, iontophoretic techniques, etc. can be employed to make safe and effective drug delivery systems which are regulatory compliant.

Dermatology mycology diagnostics in Ireland: National deficits identified in 2022 that are relevant internationally

BACKGROUND

Conventional testing methods for dermatophytes are time-consuming, and resource limitations in our institution have prompted curtailed access to these diagnostics.

OBJECTIVES

Evaluation of our hospital's dermatological mycology diagnostic services and similar services nationally.

METHODS

This was a retrospective observational study on skin, hair and nail mycology samples in our institution comparing twenty five-year periods (2011-2015 and 2016-2021), including analysis of dermatology clinic data and correspondence related to fungal infection. A survey of national public hospitals' laboratories was conducted to evaluate their mycology testing capabilities.

RESULTS

The total 5 year test count prior to curtailment was 4851 specimens comprising 90% (n = 4344) from general practice and 6% (n = 290) from dermatology clinics. For the 5 years post curtailment, 64.5% (582/903) of specimens were from dermatology clinics. Dermatology clinic data demonstrated doubling of attendances (for all conditions) and of correspondence related to fungal infection. During this time also, national dermatological antifungal purchasing increased 11%. Ten of 28 Irish public hospital laboratories reported the provision of in-house dermatological mycology testing, and none had routine availability of susceptibility or molecular testing of dermatophytes.

CONCLUSION

This study is the first to report an appraisal of dermatological fungal diagnostic services in Ireland. Insufficient testing capacity implies that patients are either being treated for fungal infection without appropriate diagnostic confirmation, or being left untreated because of the lack of access to diagnostics. The introduction of molecular detection methods and susceptibility systems would enhance testing capabilities and reduce the requirement for the external referral.

Strategies to improve the diagnosis and clinical treatment of dermatophyte infections

INTRODUCTION

Significant problems are associated with the diagnosis and treatment of dermatophyte infections, which constitute the most common fungal infections of the skin. Although this is a common problem in the community, there are no adequate guidelines for the management of all forms of dermatophyte infections. Even if dermatophytes are correctly diagnosed, they sometimes exhibit poor susceptibility to several antifungal compounds. Therefore, long-term treatment may be needed, especially in immunosuppressed patients, for whom antifungal pharmacotherapy may be inconvenient owing to allergies and undesirable drug interaction-related effects.

AREAS COVERED

In this review article, problems related to the diagnosis and treatment of dermatophyte infections have been discussed, and suggestions to resolve these problems have been presented.

EXPERT OPINION

Pretreatment microscopic or mycological examinations should be performed for dermatophyte infections. In treatment-refractory cases, antifungal-resistant strains should be determined using antifungal susceptibility testing or via molecular methods. Natural herbal, laser, and photodynamic treatments can be used as alternative treatments in patients who cannot tolerate topical and systemic antifungal treatments.

Detection of emerging genotypes in Trichophyton mentagrophytes species complex: A proposal for handling biodiversity in dermatophytes

A resistant and hypervirulent dermatophyte from India has been described as a taxonomic novelty, Trichophyton indotineae, a species of the Trichophyton mentagrophytes complex. Rapid detection and correct identification of closely similar dermatophytes with different predilections are essential for efficient clinical management. We evaluated the efficacy of rapid diagnostic methods clinical and environmental strains in the T. mentagrophytes complex. The methods included Real-time-PCR, DermaGenius, LAMP, and MALDI-ToF MS, using rDNA ITS sequences as taxonomic standard. The results show that only MALDI-ToF MS can distinguish 96.97% T. indotineae from other closely related species. The complex comprises numerous clones which may differ in anonymous markers but with similar evolutionary behavior. Therefore, we recommend to distinguish species only when they show an appreciable degree of adaptation and thus are clinically significant. The distinction of remaining clonal diversity is an epidemiological query and can be solved by haplotype numbering.

OUP accepted manuscript

The increasing incidence and changing epidemiology of invasive fungal infections continue to present many challenges to their effective management. The repertoire of antifungal drugs available for treatment is still limited although there are new antifungals on the horizon. Successful treatment of invasive mycoses is dependent on a mix of pathogen-, host- and antifungal drug-related factors. Laboratories need to be adept at detection of fungal pathogens in clinical samples in order to effectively guide treatment by identifying isolates with acquired drug resistance. While there are international guidelines on how to conduct in vitro antifungal susceptibility testing, these are not performed as widely as for bacterial pathogens. Furthermore, fungi generally are recovered in cultures more slowly than bacteria, and often cannot be cultured in the laboratory. Therefore, non-culture-based methods, including molecular tests, to detect fungi in clinical specimens are increasingly important in patient management and are becoming more reliable as technology improves. Molecular methods can also be used for detection of target gene mutations or other mechanisms that predict antifungal drug resistance. This review addresses acquired antifungal drug resistance in the principal human fungal pathogens and describes known resistance mechanisms and what in-house and commercial tools are available for their detection. It is emphasized that this approach should be complementary to culture-based susceptibility testing, given the range of mutations, resistance mechanisms and target genes that may be present in clinical isolates, but may not be included in current molecular assays.

Whole genome sequences of two Trichophyton indotineae clinical isolates from India emerging as threats during therapeutic treatment of dermatophytosis

In the current study, we report the genome sequence of two different clinical isolates from India, Trichophyton indotineae UCMS-IGIB-CI12 and Trichophyton indotineae UCMS-IGIB-CI14. The resulting genome assembly achieved a 143-fold coverage in 824 contigs for T. indotineae UCMS-IGIB-CI12 and a 136-fold coverage in 904 contigs for T. indotineae UCMS-IGIB-CI14. Both the clinical isolates contain a c.1342G>A mutation corresponding to Ala448Thr amino acid substitution in erg1 and exhibit an intermittent drug response to terbinafine. Comparative genomics analysis with available genomes of Trichophyton interdigitale/Trichophyton mentagrophytes species complex revealed a similar genome architecture and identified large number of genes associated with virulence and pathogenicity, namely, lipases, proteases, LysM domain-containing factors, carbon metabolism enzymes and cytochrome P450 enzymes, in all the genomes. An analysis of single amino acid polymorphisms (SAPs) in the protein sequences of subtilisin and lipase enzyme families identified a higher frequency of SAPs in functionally important proteins, Sub3 and Sub6 and their possible use in multilocus phylogenetic analysis of T. interdigitale/T. mentagrophytes species complex. The whole genome sequences of T. indotineae clinical isolates provided in this report will, hence, serve as a key reference point for investigation of clinical strains and emerging drug resistance among dermatophytes originating from different parts of the world.

Tinea pedis-An embarrassing problem for health and beauty-A narrative review

Fungal infections present with a broad spectrum of diseases in humans (from relatively mild superficial infections of the skin and mucous membranes to the invasive or chronic infections of internal organs, which have a high mortality rate). Globally, up to 1.6 million people die each year as a result of various types of mycoses. Currently, many scientific studies focus on the best possible understanding of the aspects of the epidemiology and pathogenesis of invasive mycoses and effective methods to combat them. However, mycoses of the skin and its appendages remain a relatively less explored area. In some communities, superficial mycoses are a frequent problem as they affect nearly 70% of the population, an example of which is the athlete's foot. It involves the nails (onychomycosis) and skin (tinea pedis). It is mainly caused by keratin-decomposing dermatophyte fungi. Less often, infections are caused by non-dermatophyte moulds (Fusarium, Aspergillus, Scopulariopsis) or yeasts. Several factors have been listed as having substantial influence on the development of dermatophytosis, including those related to climate, season, geographical region, as well as to demography, socioeconomic and cultural customs, professions or contact with animals. In this review, we summarise the current knowledge about aetiology, epidemiology, diagnostics and therapy of tinea pedis with a special focus to the role of podologic management in spreading, prevention and therapy of mycoses. The article presents up-to-date knowledge on the management of the patient from the diagnosis, treatment and skincare, to counselling on how to prevent fungal skin infections in the long term.