Terbinafine Resistance Research Articles

Trichophyton mentagrophytes ITS Genotype VIII/Trichophyton indotineae Infection and Antifungal Resistance in Bangladesh

Trichophyton (T.) mentagrophytes ITS genotype VIII, also known as Trichophyton indotineae, is a new species of the T. mentagrophytes/T. interdigitale complex and its first records, albeit under a different species name, are from the Indian subcontinent, Middle Eastern Asia, and West Asia. T. mentagrophytes genotype VIII (T. indotineae) has spread globally and has now been documented in over 30 countries. The aim of this study was to investigate the occurrence and proportion of terbinafine- and itraconazole-resistant isolates of T. mentagrophytes ITS genotype VIII (T. indotineae) in Bangladesh. This was part of an official collaborative project between IADVL (Indian Association of Dermatologists, Venereologists, and Leprologists) and Bangabandhu Sheikh Mujib Medical University (BSMMU), Bangladesh. Over a period of 6 months, ninety-nine patients of chronic recalcitrant tinea corporis were recruited from BSMMU hospital. Species identification was performed by fungal culture and morphological observation of the upper and lower surfaces of fungal colonies, as well as by using fluorescent microscopy. In addition, a PCR (polymerase chain reaction)-ELISA was performed to group the patients into those with the T. mentagrophytes/T. interdigitale complex. The internal transcribed spacer (ITS) gene was sequenced. Samples were tested for resistance to terbinafine and itraconazole by mutational analyses of the squalene epoxidase (SQLE) and the ergosterol 11B (ERG11B) genes. A total of 79/99 samples showed a positive culture. In 76 of these isolates, T. mentagrophytes ITS genotype VIII (T. indotineae) could be reliably identified both by culture and molecular testing. Resistance testing revealed terbinafine resistance in 49 and itraconazole resistance in 21 patients. Among these, 11 patients were resistant to both the antifungal agents. Mutations L393S, L393F, F397L, and F397I of the SQLE gene were associated with terbinafine resistance. Resistance to itraconazole could not be explained by mutations in the ERG11B gene. Infections with T. mentagrophytes ITS genotype VIII (T. indotineae) have become a public health issue with potentially global ramifications. About 62% of samples from Bangladesh showed resistance to terbinafine, making oral itraconazole the most effective drug currently available, although resistance to itraconazole and both terbinafine and itraconazole also exists.

In vitro and silico activity of piperlongumine against azole-susceptible/resistant Aspergillus fumigatus and terbinafine-susceptible/resistant Trichophyton species

In recent years, the widespread emergence of drug resistance in yeasts and filamentous fungi to existing antifungal armamentariums has become a severe threat to global health. There is also concern regarding increased rates of azole resistance in Aspergillus fumigatus and Terbinafine resistance in Trichophyton species. To overcome this concern of resistance to regular therapies, new antifungal drugs with novel and effective mechanisms are crucially needed. Herbal remedies may be promising strategies for the treatment of resistant infections. We aimed to investigate the in vitro and silico activity of piperlongumine against clinical azole susceptible/resistant A. fumigatus and terbinafine-susceptible/resistant Trichophyton species. In the current study, piperlongumine demonstrated potent antifungal activity, with minimum inhibitory concentrations (MICs) ranging from 0.016-4 μg/mL against Trichophyton isolates and 0.25-2 μg/mL for A. fumigatus isolates. Additionally, molecular docking studies indicated that piperlongumine has a strong binding affinity to the active sites of squalene epoxidase and sterol 14-alpha demethylase. However, further studies are warranted to correlate these findings with clinical outcomes and provide the basis for further investigations to pave the way for developing novel antifungal agents.

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.

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

ABSTRACTBackgroundTerbinafine 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.ObjectivesThe aim of this study was to understand newly discovered resistance in two Australian strains of Trichophyton interdigitale.Patients/MethodsResistance 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.ResultsThis 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.ConclusionsModelling 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.

Pharmacies Counselling of Patients in the Era of Antifungal Resistance.

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. 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. 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. 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. 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.

49702 A longitudinal cohort study of squalene epoxidase gene mutations in U.S. onychomycosis patients from 2022 to 2023 – Implications for terbinafine resistance

49702 A longitudinal cohort study of squalene epoxidase gene mutations in U.S. onychomycosis patients from 2022 to 2023 – Implications for terbinafine resistance

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.

Treatments for Onychomycosis: A Bibliometric Analysis

Introduction: Oral antifungals were the earliest treatments to receive approval for the management of onychomycosis and have a long-standing record to support their efficacy. Topical antifungals and device-based treatments have been explored and some implemented in more recent years as alternatives to traditional oral antifungals. The present bibliometric analysis summarizes trends in publication frequency for onychomycosis treatment modalities over time and characterizes their body of literature in terms of types of studies available and relative level of evidence. Methods: A comprehensive literature search was performed using Web of Science and SCOPUS databases. Results: Covering all publications from 1970 to present day, our search identified oral therapeutics n = 295 articles (n = 63 randomized control trials [RCTs]), topical therapeutics n = 358 articles (n = 72 RCTs), and device-based treatments n = 158 articles (n = 37 RCTs). Spikes in research activity surround FDA approval of therapeutics for each treatment modality. Research activity within the last decade has focused on topical and device-based treatments. Evidence for efficacy of device-based treatments is lacking from relatively few high-quality RCTs. Conclusion: With growing concern for non-dermatophyte mold onychomycosis and terbinafine resistance, researchers should validate the efficacy and safety of device-based treatments with high-quality studies.

Twenty Years in EUCAST Anti-Fungal Susceptibility Testing: Progress & Remaining Challenges.

Since its inception in 2002, the EUCAST Antifungal Susceptibility Testing Subcommittee (AFST) has developed and refined susceptibility testing methods for yeast, moulds and dermatophytes, and established epidemiological cut-off values and breakpoints for antifungals. For yeast, three challenges have been addressed. Interpretation of trailing growth in fluconazole susceptibility testing, which has been proven without impact on efficacy if below the 50% endpoint. Variability in rezafungin MIC testing due to laboratory conditions, which has been solved by the addition of Tween 20 to the growth medium in E.Def 7.4. And third, interpretation of MICs for rare yeast with no breakpoints, where recommendations have been established for MIC-based clinical advice. For moulds, refinements include the validation of spectrophotometer reading for A. fumigatus to facilitate objective MIC determination, and for dermatophytes the establishment of a microdilution method with automated reading and a selective medium to minimise the risk of contaminations. Recent initiatives involve development and validation of agar-based screening assays for detection of potential azole and echinocandin resistance in A. fumigatus and Aspergillus species, respectively, and of terbinafine resistance in Trichophyton species. Moreover, the development of a EUCAST guidance document for molecular resistance testing represents an advancement, particularly for identifying target gene alterations associated with resistance. In summary, EUCAST AFST continues to play a pivotal role in standardizing AFST and facilitating accurate interpretation of susceptibility data for clinical decision-making. Adoption of EUCAST breakpoints for commercial test methods, however, requires thorough validation to ensure concordance with EUCAST reference testing species-specific MIC distributions.

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

There is a concerning rise in antifungal-resistant dermatophytosis globally, with resistance to terbinafine conferred by point mutations in the squalene epoxidase (SQLE) gene. Report changes in the prevalence and profile of SQLE mutations in onychomycosis patients in the United States. 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). 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. The prevalence of SQLE mutations among onychomycosis patients with Trichophyton infections may be underestimated. Older individuals may have a higher risk.

Terbinafine-resistant T. indotineae due to F397L/L393S or F397L/L393F mutation among corticoid-related tinea incognita patients.

Tinea incognita (TI) can mimic other dermatoses, presenting a diagnostic challenge for dermatologists. In some uncertain cases, it is crucial to accurately identify the causative agent using internal transcribed spacer (ITS) sequencing. The global issue of drug-resistant dermatophytosis is increasing, with Trichophyton (T.) indotineae being the main cause. This study presents four cases of TI (diagnosed as eczema) by terbinafine-resistant T.indotineae strains and reviews the current global TI epidemiology based on geographical continent and related conditions. Furthermore, squalene epoxidase (SQLE)-associated resistance mechanisms are evaluated. Lesions caused by terbinafine-resistant T.indotineae strains do not respond to allylamine antifungals, thus allowing the infection to spread. Among T.indotineae isolates, the SQLE F397L substitution is the most prevalent mutation contributing to azole resistance. F397L and L393F replacements in SQLE were detected in all isolates that exhibited high-level resistance. L393S was seen in isolates with low-resistant strains. Interestingly, and for the first time, an L393F amino acid substitution in the SQLE gene product was detected in the Iranian clinical T.indotineae strain. Also, a genomics-based update on terbinafine resistance that focuses on T.indotineae is discussed in this study.

Increased terbinafine resistance among clinical genotypes of Trichophyton mentagrophytes/T. interdigitale species complex harboring squalene epoxidase gene mutations

Terbinafine resistance has become epidemic as an emerging problem in treatment of dermatohpytosis. This could be attributed in part to a point mutation in the squalene epoxidase (SQLE) gene. In this study, point mutations in the SQLE gene were studied in T. rubrum and T. mentagrophytes/T. interdigitale species complex as two main causative agents of dermatophytosis. Antifungal susceptibility of clinical isolates of T. rubrum (n = 27) and T. mentagrophytes/T. interdigitale (n = 56) was assessed using the M38–3rd edition CLSI method. The SQLE gene and ITS region were sequenced for all the fungal strains, and the mutation sites and genotypes of the terbinafine-resistant strains were characterized. The results demonstrated that, in T. rubrum, the minimum inhibitory concentration of terbinafine (MIC50 and MIC90) was 0.03 μg/ml, and the geometric mean (G mean) concentration was 0.02. For the T. mentagrophytes complex, the MIC50 and MIC90 were 0.03 and 1.0 μg/ml, respectively, and the G mean concentration was 0.04 μg/ml. Four out of the five resistant strains were T. indotineae harboring the F397L and Q408L mutations, while the last one was T. mentagrophytes genotype VII, which harbors the F397L mutation. T. indotineae was the prominent causative agent of terbinafine resistance, with 80 % of the isolates, and T. mentagrophytes genotype VII was introduced as a new genotype in the terbinafine-resistant T. mentagrophytes complex. Our findings further substantiate the importance of antifungal susceptibility testing in selecting the choice of drug for effective treatment of dermatophytosis and highlight the importance of screening dermatophyte species for point mutations responsible for newly developed resistant strains to improve the current knowledge of overcoming infections caused by resistant species.

Dermatomycoses: topical and systemic antifungal treatment

Topical antifungals with activity against dermatophytes include amorolfine, allylamines, azoles, ciclopiroxolamine, and tolnaftate. Polyene antimycotics, such as amphotericinB and nystatin, alternatively, miconazole are suitable for yeast infections of the skin and mucous membranes. For severe yeast infections of the skin and mucous membranes, oral triazole antimycotics, such as fluconazole and itraconazole, are used. Pityriasis versicolor is treated topically with antimycotics, and in severe forms also orally with itraconazole, alternatively fluconazole. Terbinafine, itraconazole and fluconazole are currently available for the systemic treatment of severe dermatophytoses, tinea capitis and onychomycosis. In addition to proven therapeutic regimens, unapproved (off-label use) intermittent low-dose therapies are increasingly being used, particularly in onychomycosis. Oral antimycotics for the treatment of tinea capitis and onychomycosis in children and adolescents can only be used off-label in Germany. In general, any oral antifungal treatment should always be combined with topical antifungal therapy. In tinea corporis and tinea cruris caused by Trichophyton (T.) mentagrophytes ITS (internal transcribed spacer) genotype VIII (T.indotineae), there is usually terbinafine resistance. Identification of the species and genotype of the dermatophyte and resistance testing are required. The drug of choice for T.mentagrophytes ITS genotype VIII dermatophytoses is itraconazole. In individual cases, treatment-refractory onychomycosis may be due to terbinafine resistance of T.rubrum. Here too, resistance testing and alternative treatment with itraconazole should be considered. Therapy monitoring should be carried out culturally and, if possible, using molecular methods (polymerase chain reaction). Alternative treatment options include laser application, and photodynamic therapy (PDT).

Epidemiological trends, antifungal drug susceptibility and SQLE point mutations in etiologic species of human dermatophytosis in Al-Diwaneyah, Iraq

Dermatophytes show a wide geographic distribution and are the main causative agents of skin fungal infections in many regions of the world. Recently, their resistance to antifungal drugs has led to an obstacle to effective treatment. To address the lack of dermatophytosis data in Iraq, this study was designed to investigate the distribution and prevalence of dermatophytes in the human population and single point mutations in squalene epoxidase gene (SQLE) of terbinafine resistant isolates. The identification of 102 dermatophytes isolated from clinical human dermatophytosis was performed through morphological and microscopic characteristics followed by molecular analysis based on ITS and TEF-1α sequencing. Phylogeny was achieved through RAxML analysis. CLSI M38-A2 protocol was used to assess antifungal susceptibility of the isolates to four major antifungal drugs. Additionally, the presence of point mutations in SQLE gene, which are responsible for terbinafine resistance was investigated. Tinea corporis was the most prevalent clinical manifestation accounting for 37.24% of examined cases of dermatophytosis. Based on ITS, T. indotineae (50.98%), T. mentagrophytes (19.61%), and M. canis (29.41%) was identified as an etiologic species. T. indotineae and T. mentagrophytes strains were identified as T. interdigitale based on TEF-1α. Terbinafine showed the highest efficacy among the tested antifungal drugs. T. indotineae and T. mentagrophytes showed the highest resistance to antifungal drugs with MICs of 2–4 and 4 μg/mL, while M. canis was the most susceptible species. Three of T. indotineae isolates showed mutations in SQLE gene Phe397Leu substitution. A non-previously described point mutation, Phe311Leu was identified in T. indotineae and mutations Lys276Asn, Phe397Leu and Leu419Phe were diagnosed in T. mentagrophytes XVII. The results of mutation analysis showed that Phe397Leu was a destabilizing mutation; protein stability has decreased with variations in pH, and point mutations affected the interatomic interaction, resulting in bond disruption. These results could help to control the progression of disease effectively and make decisions regarding the selection of appropriate drugs for dermatophyte infections.

Trichophyton indotineae and other terbinafine-resistant dermatophytes in North America.

Dermatophyte infections (a.k.a. ringworm, tinea) affect an estimated 20%-25% of the world's population. In North America, most dermatophytoses are caused by Trichophyton rubrum or Trichophyton mentagrophytes species complexes. Severe and antifungal-resistant dermatophytoses are a growing global public health problem. A new species of the T. mentagrophytes species complex, Trichophyton indotineae, has recently emerged and is notable for the severe infections it causes, its propensity for antifungal resistance, and its global spread. In this issue of the Journal of Clinical Microbiology, C. F. Cañete-Gibas, J. Mele, H. P. Patterson, et al. (J Clin Microbiol 61:e00562-23, 2023, https://doi.org/10.1128/JCM.00562-23) summarize the results of speciation and AFST performed on North American dermatophyte isolates received at a fungal diagnostic reference laboratory. Within their collection, 18.6% of isolates were resistant to terbinafine (a first-line oral antifungal for dermatophytoses), and similar proportions of T. rubrum and T. indotineae demonstrated terbinafine resistance. The authors also found that T. indotineae has been present in North America since at least 2017. These findings highlight the importance of increased surveillance efforts to monitor trends in severe and antifungal-resistant dermatophytoses and the need for antifungal stewardship efforts, the success of which is contingent upon improving laboratory capacity for dermatophyte speciation and AFST.

Recurrent tinea corporis generalisata due to Terbinafine-resistant Trichophyton rubrum strain : Long-term treatment with super bioavailability itraconazole

For more than 30years, an 82-year-old man has been suffering from tinea corporis generalisata in the sense of Trichophyton rubrum syndrome. The patient received long-term treatment with terbinafine. Fluconazole had no effect. There was an increase in liver enzymes with itraconazole. Super bioavailability (SUBA) itraconazole was initially not tolerated. Atherapy attempt with voriconazole was successful, but was stopped due to side effects. The Trichophyton (T.)rubrum strain isolated from skin scales was tested for terbinafine resistance using the breakpoint method and found to be (still) sensitive. Sequencing of the squalene epoxidase (SQLE) gene revealed apreviously unknown point mutation of the codon for isoleucine ATC→ACC with amino acid substitution I479T (isoleucine479 threonine). Long-term therapy with terbinafine 250 mg had been given every 3days since 2018. In addition, bifonazole cream, ciclopirox solution, and occasionally terbinafine cream were used. The skin condition was stable until an exacerbation of the dermatophytosis in 2021. There were erythematosquamous, partly atrophic, centrifugal, scaly, confluent plaques on the integument and the extremities. Fingernails and toenails had white to yellow-brown discoloration, and were hyperkeratotic and totally dystrophic. T.rubrum was cultured from skin scales from the integument, from the feet, from nail shavings from the fingernails and also toenails and detected by PCR. In the breakpoint test, the T.rubrum isolates from tinea corporis and nail samples showed aminimum inhibitory concentration (MIC) of 0.5 µgml-1 (terbinafine resistance in vitro). Sequencing of the SQLE gene of the T.rubrum isolate revealed evidence of afurther point mutation that led to amino acid substitution I479V (isoleucine 479 valine). Long-term therapy was started with SUBA itraconazole: 14days 2 × 1capsule daily, then twice weekly administration of 2 × 50 mg. During breaks in therapy, the mycosis regularly flared up again. Finally, 50 mg SUBA itraconazole was given 5days aweek, which completely suppressed the dermatophytosis. Topically, ciclopirox and miconazole cream were used alternately. In conclusion, in the case of recurrent and therapy-refractory dermatophytoses caused by T.rubrum, terbinafine resistance must also be considered in individual cases. An in vitro resistance test and point mutation analysis of the squalene epoxidase gene confirms the diagnosis. Itraconazole, also in the form of SUBA itraconazole, is the drug of choice for the oral antifungal treatment of these patients.

Genomic Analysis of Antifungal Drug Resistance Induced in Trichophyton rubrum After Prolonged Culture with Terbinafine.

In this study, we induced terbinafine (TRF) resistance in a T. rubrum strain in vitro for 18months then compared the genomes of the TRF-resistant (N42-3) and TRF-susceptible wild-type (N42WT) strains to identify mutations. In the SQLE gene, N42WT had no mutation while N42-3 had a F397L mutation. We sequenced approximately 22.53Mb of the genomes of the N43WT and N42-3 strains. Other than the F397L mutation in SQLE, there were three other genetic mutations in three different genes that were found in N42-3, but not in N43WT; however, these three mutations were not detected in other TRF-resistant T. rubrum strains. From this genome sequencing analysis, the only variation that was confirmed to be associated with drug resistance in the genome of the TRF-resistant T. rubrum was a hotspot mutation in SQLE.

Identification of Microbial Community in Otomycosis by Metagenomic Next Generation Sequencing (mNGS): Potential Implication of Treatment with Terbinafine.

The present study was designed to identify the microbial community as well as to analyze its diversity by means of metagenomic Next Generation Sequencing (mNGS) in 17 patients with otomycosis treated with terbinafine in the Department of Otolaryngology of Shandong Provincial Hospital from June 2021 to June 2022, so as to evaluate the relationship between microbial community and terbinafine resistance. Those 17 patients were divided into two groups, i.e., Terbinafine Effective Group (TEG, n = 14 cases) and Terbinafine Resistance Group (TRG, n = 3 cases) according to the therapy effect, whose microbial community of secretion of external auditory canal was identified using mNGS. We found that the sequence of bacteria was significantly more than that of fungi and, whereas, the difference between the two groups of bacteria was not significant. There were significant differences in fungal community between the two groups. Aspergillus was the main pathogenic fungus of TEG patients while Malassezia was a dominant fungus in TRG patients. In conclusion, the results from this work indicate that Aspergillus terreusis is the main pathogenic fungus in this cohort of otomycosis patients and MNGS sequencing can offer comprehensive information about the microbial community of otomycosis. The fungus community dominated by Malassezia is more likely to be resistant to terbinafine, which provides certain guidance for clinical treatment of otomycosis with terbinafine.

Increased copy number of the target gene squalene monooxygenase as the main resistance mechanism to terbinafine in Leishmania infantum

We use here two genomic screens in an attempt to understand the mode of action and resistance mechanism of terbinafine, an antifungal contemplated as a potential drug against the parasite Leishmania. One screen consisted in in vitro drug evolution where 5 independent mutants were selected step-by-step for terbinafine resistance. Sequencing of the genome of the 5 mutants revealed no single nucleotide polymorphisms related to the resistance phenotype. However, the ERG1 gene was found amplified as part of a linear amplicon, and transfection of ERG1 fully recapitulated the terbinafine resistance phenotype of the mutants. The second screen, Cos-seq, consisted in selecting a gene overexpression library with terbinafine followed by the sequencing of the enriched cosmids. This screen identified two cosmids derived from loci on chromosomes 13 and 29 encoding the squalene monooxygenase (ERG1) and the C8 sterol isomerase (ERG2), respectively. Transfection of the ERG1-cosmid, but not the ERG2-cosmid, produced resistance to terbinafine. Our screens suggest that ERG1 is the main, if not only, target for terbinafine in Leishmania and amplification of its gene is the main resistance mechanism.

Trichophyton indotineae, from epidemiology to therapeutic

Trichophyton indotineae is a newly described dermatophyte species. This fungal pathogen has recently emerged in India and is responsible for chronic or recurrent widespread superficial infections. Resistance to terbinafine is frequently associated to this pathogen and is related to point mutations in the gene encoding the squalene epoxidase. T. indotineae infections have been reported outside India, highlighting the risk of worldwide diffusion of this microorganism. Species identification and antifungal susceptibility determination are key points for infection control but still remain challenging. Systemic treatment is usually required and itraconazole is frequently prescribed in case of terbinafine resistance. This review summarizes main features of T. indotineae taxonomy, epidemiology, clinical manifestations, identification, antifungal profile, treatment and prevention.