New Sources of Resistance to Terbinafine Revealed and Squalene Epoxidase Modelled in the Dermatophyte Fungus Trichophyton interdigitale From Australia.

BACKGROUND: Terbinafine is widely used to treat onychomycosis caused by dermatophyte fungi. Terbinafine resistance in recent years is causing concern. Resistance has so far been associated with single-nucleotide substitutions in the DNA sequence of the enzyme squalene epoxidase (SQLE) but how this affects SQLE functionality is not understood. OBJECTIVES: The aim of this study was to understand newly discovered resistance in two Australian strains of Trichophyton interdigitale. PATIENTS/METHODS: Resistance to terbinafine was tested in four newly isolated strains. Three-dimensional SQLE models were prepared to investigate how the structure of their SQLE affected the binding of terbinafine. RESULTS: This study found the first Australian occurrences of terbinafine resistance in two T. interdigitale strains. Both strains had novel deletion mutations in erg1 and frameshifts during translation. Three-dimensional models had smaller SQLE proteins and open reading frames as well as fewer C-terminal α-helices than susceptible strains. In susceptible strains, the lipophilic tail of terbinafine was predicted to dock stably into a hydrophobic pocket in SQLE lined by over 20 hydrophobic amino acids. In resistant strains, molecular dynamics simulations showed that terbinafine docking was unstable and so terbinafine did not block squalene metabolism and ultimately ergosterol production. The resistant reference strain ATCC MYA-4438 T. rubrum showed a single erg1 mutation that resulted in frameshift during translation, leading to C-terminal helix deletion. CONCLUSIONS: Modelling their effects on their SQLE proteins will aid in the design of potential new treatments for these novel resistant strains, which pose clinical problems in treating dermatophyte infections with terbinafine.

Now that griseofulvin is not available, what to do with tinea capitis treatments?

INTRODUCTION: Griseofulvin, discovered in 1939 and commercially available since 1959, was the first oral antifungal agent effective against dermatophytosis, particularly tinea capitis. Although it was eventually superseded by azole antifungals due to its long treatment duration and reliance on keratopoiesis, griseofulvin remains notable for its effectiveness and safety in treating tinea capitis, especially when caused by Microsporum canis. However, due to a decline in cases and commercial unavailability, alternative treatments are now required. AREAS COVERED: The following topics regarding to other treatments were discussed: (I) The efficacy of alternative antifungal agents such as terbinafine, itraconazole, and fluconazole, in the treatment of tinea capitis. (II) The use and role of topical therapies. (III) Experience in the management of tinea capitis. EXPERT OPINION: The usefulness of oral terbinafine as a replacement for griseofulvin in the treatment of tinea capitis and why it is the preferred drug in elderly patients was discussed. Challenges with Microsporum spp. and the use of fluconazole in pediatric patients were also analyzed. Support for the use of topical treatment as an adjunctive treatment for tinea capitis was highlighted.

Uncovering the Hidden Potential of Phytoene Production by the Fungus Blakeslea trispora.

Phytoene is an uncommon linear carotene within the carotenoid group as it is colorless due to its short chromophore. Recent research constitutes a relatively new area which has emerged from phytoene's importance as a major dietary carotenoid promoting health and appearance. Its resources point to the potential of biotechnological production systems. Our work has been designed to study the efficacy of two colored carotenoid biosynthesis inhibitors, diphenylamine and 2-methyl imidazole, and one sterol biosynthesis inhibitor, terbinafine, to modify the metabolic flux in mated cultures of Blakeslea trispora to achieve maximum phytoene production. Bioprocess kinetics optimized by response surface methodology and monitored by high-performance liquid chromatography revealed maximum phytoene content (5.02 mg/g dry biomass) and yield (203.91 mg/L culture medium) comparable or even higher than those reported for other potent phytoene microbial producers. The in vivo antioxidant activity of phytoene-rich carotenoid extract from fungal cells was also considered and discussed.

Terbinafine Resistance in Trichophyton Strains Isolated from Humans and Animals: A Retrospective Cohort Study in Italy, 2016 to May 2024.

Background: In recent decades, globalization and international migration have increased the spread of infectious agents, including dermatophytes. Although considered minor infections, dermatophytoses are highly contagious, and they significantly reduce the quality of life, inducing itching, burning, sleep disturbances, and even depressive states. Moreover, the increasing resistance to antifungals threats the public health and burdens the costs for the healthcare system. Methods: DermaGenius® Resistance Multiplex real-time PCR assay allowed to analyze the terbinafine susceptibility/resistance of 172 Trichophyton strains, which were isolated from human and animal samples collected from 2016 to May 2024 and previously identified by Sanger sequencing. Results: All the 11 animal strains belonged to the T. interdigitale/T. mentagrophytes complex and tested terbinafine sensitive. Out of 161 human strains, 9 (5.6%) showed terbinafine resistance and 7 (4.3%) were identified as T. indotineae. Conclusions: This study provides preliminary data about behavior toward antifungals in animals and finalizes the scientific information currently available about human strains, highlighting the importance of the One Health concept. Moreover, it supports the relevant role of T. indotineae as an emerging dermatophyte with high proportion of terbinafine resistance.

Pharmacies Counselling of Patients in the Era of Antifungal Resistance.

BACKGROUND: Tinea pedis is one of the most prevalent superficial fungal infections. Initial antifungal treatment is often acquired over-the-counter (OTC) without previous consultation with a physician. OBJECTIVE: Lately, increasing antifungal terbinafine resistance has been documented in Denmark and globally and it is therefore of interest to assess how Danish pharmacies advise customers with tinea pedis. METHODS: One hundred Danish pharmacies were randomly selected and an employee interviewed from each. A structured question guide was followed, with the possibility to add further comments. RESULTS: Interviews of 94 pharmacies were conducted. Six pharmacies never replied. Terbinafine as standard dose or cutaneous solution terbinafine one time application (Lamisil Once (R)) were recommended by 99% of the pharmacy employees as first-line treatment. The customer was advised to seek medical attention when tinea pedis was recurring (93%), or when treatment duration was > 2 weeks (77%). The majority (88%) of the pharmacy employees had no knowledge about antifungal resistance. CONCLUSION: Only few pharmacy employees were aware of the current problem of antifungal resistance and the majority advised costumers to initiate treatment using OTC topical terbinafine. The problem of emerging antifungal resistance requires attention in order to provide customers with tinea pedis effective treatment and prevent further societal spread of resistance to antifungals.

Case of tinea corporis caused by a terbinafine-sensitive Trichophyton indotineae strain in a Vietnamese worker in Japan.

A 42-year-old Vietnamese egg factory worker in Ishikawa prefecture, Japan, presented with itchy concentric erythema on the trunk and left calf. The lesions tested positive by direct potassium hydroxide examination, and two fungal strains were isolated. The isolates produced conidia abundantly and were morphologically indistinguishable from Trichophyton mentagrophytes/interdigitale, but were identified as Trichophyton indotineae by internal transcribed spacer sequence of ribosomal DNA. The lesions were refractory to treatment with topical luliconazole (LLCZ) cream for 4 weeks but subsided with oral itraconazole (ITCZ) 100 mg/day for 4 weeks in combination with topical lanoconazole (LCZ) cream. The lesions recurred 6 weeks after discontinuation of oral ITCZ, and an additional isolate was cultured. The minimum inhibitory concentrations of antimycotics for the isolate cultured at the first visit were: terbinafine (TBF) 0.03 µg/mL, ITCZ 0.015 µg/mL, LLCZ 0.0005 µg/mL, and LCZ 0.002 µg/mL. No TBF-resistant mutation in the amino acid sequence of squalene epoxidase, i.e., Leu 393 Ser/Phe or Phe 397 Leu, was detected in the isolate. The reason for recalcitrance in this case, despite the isolate's sensitivity to antimycotics, was unclear. Possible factors include insufficient use of the antimycotics, incomplete removal of abundantly produced conidia from the lesions, the patient's environment, and a language gap between the patient and physician hindering communication.

Analysis of clinical characteristics of terbinafine-induced subacute cutaneous lupus erythematosus.

INTRODUCTION: Terbinafine may cause subacute cutaneous lupus erythematosus (SCLE), and we aimed to analyze its clinical characteristics. METHODS: We collected literature on terbinafine-induced SCLE from 1997 to 2023 for retrospective analysis. Thirty-seven patients (33 females and 4 males) were included. RESULTS: The patients have a median age of 49.5 years (range 18-79) and onset time of 5 weeks (range 1-12). SCLE is mainly manifested as annular erythematous (83.3%), scaly erythematous (44.4%), and maculopapular erythematous (13.9%). Mainly, histopathological manifestations are lymphocytic infiltrate (55.6%), hyperkeratosis (38.9%) and keratinocyte necrosis (38.9%). Positive immunological parameters mainly include antinuclear antibody (100.0%), anti-Ro/SSA antibody (94.1%), and anti-La/SSB antibody (72.2%). Past medical history usually includes photosensitivity (33.3%), inflammatory disease (33.33%), and lupus erythematosus (12.1%). Symptoms are completely resolved within a median time of 35 days (range 7-84) after discontinuation of terbinafine and treatment with topical corticosteroids, systemic corticosteroids, hydroxychloroquine, and immunosuppressant. No recurrence was observed within 12 months (range 1.5-48) of follow-up. CONCLUSION: These results suggest that terbinafine-induced SCLE should be comprehensively diagnosed based on clinical symptoms, histopathological manifestations, immunological parameters, and past medical history. Terbinafine should be immediately discontinued when SCLE occurs, while systemic and topical corticosteroids combined with hydroxychloroquine may be an effective treatment.

Prolonged treatment of dermatophytosis caused by Trichophyton indotinea with terbinafine or itraconazole impacts better outcomes irrespective of mutation in the squalene epoxidase gene.

BACKGROUND: Over the past decades, the increasing incidence of recurrent dermatophytosis associated with terbinafine-resistant Trichophyton has posed a serious challenge in management of dermatophytosis. Independent reports of failure of treatment and high minimum inhibitory concentrations (MIC) of antifungals are available, but data correlating MIC and clinical outcomes is still sparse. Therefore, the present study was conducted to evaluate the outcomes of systemic treatment of dermatophytosis and its correlation with MIC of the etiological agents isolated from such patients. METHODS: Retrospective analysis of 587 consecutive patients with dermatophytosis was done from March 2017 to March 2019. Demographic and clinical details of the patients were noted, along with the results of direct microscopy and fungal culture. The isolates were identified by sequencing the internal transcribed spacer region of rDNA. Antifungal susceptibility testing was performed following the CLSI M38 protocol. Mutation in the squalene epoxidase (SE) gene was detected by DNA sequencing and ARMS-PCR. Based on the culture-positivity and prescribed systemic antifungal, patients were categorised into Group I culture-positive cases treated with systemic terbinafine and Group II culture-positive cases treated with systemic itraconazole, each for a total period of 12 weeks. RESULTS: In the present study, 477 (81.39%) were culture-positive; however, 12 weeks follow-up was available for 294 patients (Group I-157 and Group II-137) who were included for statistical analysis. In both groups [Group I-37/63 (51.4%) and Group II-14/54 (58.3%)], a better cure rate was observed if the initiation of therapy was performed within <6 months of illness. Treatment outcome revealed that if therapy was extended for 8-12 weeks, the odds of cure rate are significantly better (p < .001) with either itraconazole (Odd Ratio-15.5) or terbinafine (Odd Ratio-4.34). Higher MICs for terbinafine were noted in 41 cases (cured-18 and uncured-23) in Group I and 39 cases (cured-16 and uncured-23) in Group II. From cured (Group I-17/18; 94.4% and Group II-14/16; 87.5%) and uncured (Group I-20/23; 86.9% and Group II-21/23; 91.3%) cases had F397L mutation in the SE gene. No significant difference in cure rate was observed in patients with Trichophyton spp. having terbinafine MIC ≥ 1or <1 µg/mL (Group I-p = .712 and Group II-p = .69). CONCLUSION: This study revealed that prolonging terbinafine or itraconazole therapy for beyond 8 weeks rather than the standard 4 weeks significantly increases the cure rate. Moreover, no correlation has been observed between antifungal susceptibility and clinical outcomes. The MIC remains the primary parameter for defining antifungal activity and predicting the potency of antifungal agents against specific fungi. However, predicting therapeutic success based solely on the MIC of a fungal strain is not always reliable, as studies have shown a poor correlation between in vitro data and in vivo outcomes. To address this issue, further correlation of antifungal susceptibility testing (AFST) data with clinical outcomes and therapeutic drug monitoring is needed. It also highlights that initiation of the treatment within <6 months of illness increases cure rates and reduces recurrence. Extensive research is warranted to establish a better treatment regime for dermatophytosis.

Detection of terbinafine-resistant Trichophyton indotineae isolates within the Trichophyton mentagrophytes species complex isolated from patients in Hue City, Vietnam: A comprehensive analysis.

The Trichophyton mentagrophytes complex comprises a group of dermatophyte fungi responsible for various dermatological infections. The increasing drug resistance of this species complex, especially terbinafine resistance of Trichophyton indotineae, is a major concern in dermatologist practice. This study provides a comprehensive analysis of T. mentagrophytes complex strains isolated from patients in Hue City, Vietnam, focusing on their phenotypic and genetic characteristics, antifungal susceptibility profiles, and molecular epidemiology. Keratinophilic fungi from dermatophytosis culture samples were identified morphologically and phenotypically, with species and genotypes confirmed by internal transcribed spacer sequencing and phylogenetic analysis. Antifungal susceptibility testing was carried out to evaluate their susceptibility to itraconazole, voriconazole, and terbinafine. The 24% (n = 27/114) of superficial mycoses were phenotypically attributed to T. mentagrophytes complex isolates. Trichophyton interdigitale, mainly genotype II*, was predominant (44.4%), followed by T. mentagrophytes genotype III* (22.2%), T. indotineae (14.8%), T. tonsurans (11.2%), and T. mentagrophytes (7.4%). While all isolates were susceptible to itraconazole and voriconazole, half of T. indotineae isolates exhibited resistance to terbinafine, linked to the Phe397Leu mutation in the SQLE protein. This study highlighted the presence of terbinafine-resistant T. indotineae isolates in Vietnam, emphasizing the need to investigate dermatophyte drug resistance and implement effective measures in clinical practice.

Species diversity within the Trichophyton mentagrophytes complex isolated from dermatophytosis in Hue City, Vietnam, was observed. Terbinafine-resistant T. indotineae isolates were detected for the first time in Vietnam, emphasizing the importance of implementing antifungal susceptibility testing to effectively manage and prevent the spread of resistant isolates.

Recognition of Antifungal-Resistant Dermatophytosis by Infectious Diseases Specialists, United States.

Antifungal-resistant dermatophyte infections have recently emerged as a global public health concern. A survey of US infectious diseases specialists found that only 65% had heard of this issue and just 39% knew how to obtain testing to determine resistance. Increased clinician awareness and access to testing for antifungal-resistant dermatophytosis are needed.

Is terbinafine an effective treatment for feline sporotrichosis?

BACKGROUND: Terbinafine has been successfully used in the treatment of human sporotrichosis; however, its effectiveness in the treatment of feline sporotrichosis is unknown. Therefore, this study aimed to describe the use of terbinafine in the treatment of feline sporotrichosis. METHODS: A cohort study was conducted in cats with sporotrichosis to assess the effectiveness and safety of terbinafine (30‒60 mg/kg/day). Clinical examination and analysis of laboratory parameters were performed monthly until clinical signs resolved or terbinafine treatment was discontinued. RESULTS: Of the 54 cats with sporotrichosis included in the study, 19 were lost during follow-up and five were withdrawn from the study due to switching to treatment with another prescription drug. Of the remaining 30 cats, 10 achieved clinical cure, with a median treatment time of 18.5 weeks. Treatment failed in 18 cases, and two cats died. Twenty-two cats had adverse reactions to terbinafine treatment, and 10 cats showed elevation of serum transaminases. LIMITATION: Loss during follow-up was high, which makes it difficult to draw accurate conclusions regarding clinical outcomes. CONCLUSION: The low rate of clinical cure observed suggests that terbinafine does not represent an effective treatment option for cases of feline sporotrichosis.

Systemic absorption and safety of topical terbinafine hydrochloride 10% solution (MOB015B): a phase 1 maximal usage trial in patients with moderate-to-severe onychomycosis.

Topical antifungals may be considered to treat onychomycosis with minimal risk of systemic side effects. In this study, we assess the safety, tolerability, systemic exposure, and pharmacokinetic characteristics of topical terbinafine hydrochloride 10% solution (MOB015B) in adults with moderate-to-severe onychomycosis. Clinically and mycologically confirmed patients with toenail onychomycosis (N = 20) were enrolled in this single-center, open-label study . Each patient had ≥50% involvement of both great toenails and at least four additional toenails affected. MOB015B was applied once daily to all toenails for 28 days. Blood was drawn on days 1, 14, and 28. Plasma concentrations of MOB015B after the first dose were quantifiable in all subjects by 24 h. Steady-state levels in plasma were reached by day 28. The mean systemic exposure on day 28 of 0.72 ng/mL for maximum plasma concentration (Cmax) was approximately 2,000 times lower than the mean plasma level of 1.39 µg/mL seen after oral administration of 250 mg terbinafine for 28 days. Adverse events (five patients), such as headache (n = 3), seasonal allergy (n = 1), and neck pain (n = 1), were considered unrelated to MOB015B; no application site reactions or study discontinuations due to an adverse event were observed. MOB015B applied to all affected toenails under maximal usage conditions for 28 days demonstrated very low levels of terbinafine in plasma (Cmax <1 ng/mL after 28 days), consistent with a favorable safety and tolerability profile. CLINICAL TRIALS: This study is registered with ClinicalTrials.gov as NCT03244280.

Dual quantitative PCR assays for the rapid detection of Trichophyton indotineae from clinical samples.

Trichophyton indotineae is an emerging species of the Trichophyton mentagrophytes complex (TMC), responsible for an epidemic of widespread hairless skin infections that is frequently (50-70%) resistant to terbinafine. In order to initiate appropriate treatment as quickly as possible without waiting for culture positivity (10-15 days) and molecular identification from the strain, we developed a dual quantitative PCR (qPCR) for the direct detection of T. indotineae in clinical samples. We first designed a T. indotineae-specific qPCR assay (TI-qPCR) targeting a single specific polymorphism in the internal transcribed spacer region. Although none of the 94 non-dermatophyte and 7 dermatophyte species were amplified, this TI-qPCR allowed amplification of other TMC species at a lower yield. With equal amounts (0.1 ng) of DNA per reaction, the mean quantitative cycle (Cq) values for T. indotineae and non-indotineae TMC were 27.9 (±0.1) and 38.9 (±0.3), respectively. Therefore, we normalized this assay against a previously validated pan-dermatophyte qPCR assay (PD-qPCR) and relied on the ΔCq [(TI-qPCR) - (PD-qPCR)] to identify T. indotineae versus other TMC species. Dual assay was validated using 86 clinical samples of culture-confirmed T. indotinea and 19 non-indotineae TMC cases. The mean ΔCq for non-indotineae TMC was 9.6 ± 2.7, whereas the ΔCq for T. indotinea was -1.46 ± 2.1 (P < .001). Setting the ΔCq at 4.5 as a cutoff value resulted in 100% specificity for the detection of T. indotineae. This dual qPCR assay quickly detects T. indotineae from skin scrapings, aiding in early diagnosis and treatment for patients with suspected infection.

Identifying the emerging species Trichophyton indotineae is long and requires to wait for culture positivity. We developed a dual qPCR strategy to detect T. indotineae directly from clinical sample with a 100% sensitivity.

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.

In vitro effects of N-acetylcysteine in combination with antifungal agents against Malassezia pachydermatis isolated from canine otitis externa.

BACKGROUND: Many clinicians prescribe antifungal agents to treat canine otitis externa (OE). However, studies evaluating the antifungal effects of N-acetylcysteine (NAC) and its combinations are limited. HYPOTHESIS/OBJECTIVES: The aim of this study was to evaluate the antifungal effects of NAC alone and in combination with other antifungal agents against Malassezia pachydermatis isolated from canine OE. MATERIALS AND METHODS: M. pachydermatis samples were collected from 13 dogs with OE. The final concentration of the inoculum suspensions of M. pachydermatis was 1-5 × 106 colony forming units/mL. The concentrations of the test compounds ketoconazole (KTZ), terbinafine (TER), nystatin (NYS) and NAC were 0.02-300 µg/mL, 0.04-80 µg/mL, 0.16-40 µg/mL and 1.25-20 mg/mL, respectively. The minimum inhibitory concentration (MIC) was measured to evaluate the susceptibility of the M. pachydermatis to KTZ, TER, NYS and NAC. The checkerboard testing method and fractional inhibitory concentration index were used to evaluate the effect of NAC in combination with KTZ, TER and NYS against M. pachydermatis. RESULTS: The MIC90 values of M. pachydermatis were 4.6875-9.375 µg/mL, 1.25 µg/mL, 5-10 µg/mL and 10 mg/mL for KTZ, TER, NYS and NAC, respectively. The synergistic effects of KTZ, TER and NYS with NAC were identified in 0/13, 2/13 and 0/13 isolates, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: NAC had an antifungal effect against M. pachydermatis but did not exert synergistic effects when used with KTZ, TER and NYS. Thus, the use of NAC alone as a topical solution could be considered an effective treatment option for canine OE involving M. pachydermatis.

The Preparation and Evaluation of a Hydrochloride Hydrogel Patch with an Iontophoresis-Assisted Release of Terbinafine for Transdermal Delivery.

Background: Terbinafine hydrochloride (TEB) is a broad-spectrum antifungal medication commonly used to treat fungal infections of the skin. This study designed a hydrogel patch assisted by an iontophoresis system to enhance the transdermal permeability of TEB, enabling deeper penetration into the skin layers. Methods: The influences of current intensity, pH levels, and drug concentration on the TEB hydrogel patch's permeability were explored using an adaptive ion electroosmosis system. The pharmacokinetic profile, facilitated by iontophoresis for transdermal permeation, was analyzed through the application of microdialysis technology. Scanning electron microscopy and transmission electron microscopy were employed to assess the impact of ion electroosmotic systems on skin integrity. Results: The cumulative drug accumulation within 8 h of the TEB hydrogel patches, assisted by iontophoresis, was 2.9 and 7.9 times higher than without iontophoresis assistance and TEB cream in the control group, respectively. TEB hydrogel patches assisted by iontophoresis can significantly increase the permeability of TEB, and the AUC(0-8 h) was 3.4 and 5.4 times higher, while the Cmax was 4.2 and 7.3 times higher than the TEB hydrogel patches without iontophoresis, respectively. This system has no significant impact on deep-layer cells. Conclusions: This system may offer a safe and effective clinical strategy for the local treatment of deep antifungal infections.