Successful treatment of resistant onychomycosis with voriconazole in a liver transplant patient

Time to Think Antifungal Resistance Increased Antifungal Resistance Exacerbates the Burden of Fungal Infections Including Resistant Dermatomycoses

Increased antifungal resistance is exacerbating the burden of invasive fungal infections, as well as potentially contributing to the increase in resistant dermatomycoses. In this commentary, we focus on antifungal drug resistance, in contrast to antibacterial resistance. We provide a brief historical perspective on the emergence of antifungal resistance and propose measures for combating this growing health concern. The increase in the incidence of invasive and cutaneous fungal infections parallels advancements in medical interventions, such as immunosuppressive drugs, to manage cancer and reduce organ rejection following transplant. A disturbing relatively new trend in antifungal resistance is the observation of several fungal species that now exhibit multidrug resistance (eg, Candida auris, Trichophyton indotineae). Increasing awareness of these multidrug-resistant species is paramount. Therefore, increased education regarding potential fungus-associated infections is needed to address awareness in the general healthcare setting, which may result in a more realistic picture of the prevalence of antifungal-resistant infections. In addition to education, increased use of diagnostic tests (eg, micro and macro conventional assays or molecular testing) should be routine for healthcare providers facing an unknown fungal infection. Two critical barriers that affect the low rates for Antifungal Susceptibility Testing (AST) are low (or a lack of) sufficient insurance reimbursement rates and the low number of qualified laboratories with the capacity to perform AST. The ultimate aim is to improve the quality of patient care through fungal identification, diagnosis, and, where appropriate, susceptibility testing. Here we propose an all-encompassing call to action to address this emerging challenge.

Antifungal Selection for the Treatment of Onychomycosis: Patient Considerations and Outcomes

Onychomycosis, a common fungal nail infection, affects >20% of adults over age 60 and >50% of people over age 70. Onychomycosis may cause pain, psychosocial problems, and secondary infections, therefore meriting treatment. This review describes the range of treatment modalities, including FDA-approved systemic drugs and topical therapies. Additionally, new and emerging oral and topical therapies are discussed. We emphasize the importance of tailoring onychomycosis therapy to individual patient characteristics, comorbidities, preferences, extent of nail involvement, and fungal species, such that physicians may optimize treatment outcomes, patient satisfaction, and safety.

Treatment of onychomycosis in an era of antifungal resistance: Role for antifungal stewardship and topical antifungal agents

A growing body of literature has marked the emergence and spread of antifungal resistance among species of Trichophyton, the most prevalent cause of toenail and fingernail onychomycosis in the United States and Europe. We review published data on rates of oral antifungal resistance among Trichophyton species; causes of antifungal resistance and methods to counteract it; and in vitro data on the role of topical antifungals in the treatment of onychomycosis. Antifungal resistance among species of Trichophyton against terbinafine and itraconazole-the two most common oral treatments for onychomycosis and other superficial fungal infections caused by dermatophytes-has been detected around the globe. Fungal adaptations, patient characteristics (e.g., immunocompromised status; drug-drug interactions), and empirical diagnostic and treatment patterns may contribute to reduced antifungal efficacy and the development of antifungal resistance. Antifungal stewardship efforts aim to ensure proper antifungal use to limit antifungal resistance and improve clinical outcomes. In the treatment of onychomycosis, critical aspects of antifungal stewardship include proper identification of the fungal infection prior to initiation of treatment and improvements in physician and patient education. Topical ciclopirox, efinaconazole and tavaborole, delivered either alone or in combination with oral antifungals, have demonstrated efficacy in vitro against susceptible and/or resistant isolates of Trichophyton species, with low potential for development of antifungal resistance. Additional real-world long-term data are needed to monitor global rates of antifungal resistance and assess the efficacy of oral and topical antifungals, alone or in combination, in counteracting antifungal resistance in the treatment of onychomycosis.

Combatting antifungal resistance: Paradigm shift in the diagnosis and management of onychomycosis and dermatomycosis

Antifungal resistance has become prevalent worldwide. Understanding the factors involved in spread of resistance allows the formulation of strategies to slow resistance development and likewise identify solutions for the treatment of highly recalcitrant fungal infections. To investigate the recent explosion of resistant strains, a literature review was performed focusing on four main areas: mechanisms of resistance to antifungal agents, diagnosis of superficial fungal infections, management, and stewardship. The use of traditional diagnostic tools such as culture, KOH analysis and minimum inhibitory concentration values on treatment were investigated and compared to the newer techniques such as molecular methods including whole genome sequencing, and polymerase chain reaction. The management of terbinafine-resistant strains is discussed. We have emphasized the need for antifungal stewardship including increasing surveillance for resistant infection.

The safety of oral antifungals for the treatment of onychomycosis

INTRODUCTION

Oral antifungals are used for the treatment of moderate-severe onychomycosis. Terbinafine and itraconazole are approved for onychomycosis treatment in North America; additionally, fluconazole is indicated for onychomycosis in Europe. Other oral antifungals such as ketoconazole and griseofulvin are no longer used for the treatment of onychomycosis due to safety concerns and relatively lower efficacy.

SEARCH STRATEGY

On 7 March 2023, we conducted a comprehensive search in PubMed and Google Scholar, while also manually examining selected article bibliographies and package inserts.

AREAS COVERED

Terbinafine, itraconazole, and fluconazole have several interactions with cytochrome-p450, and either alone, or when co-administered with other drugs these interactions can facilitate a multitude of adverse events. This article identifies possible hepatic, renal, cutaneous, cardiovascular, neurological, hemopoietic, and obstetric adverse events. We have also compared the rates of hepatotoxicity, clinically apparent liver injury, and alanine transaminase elevations between oral antifungals, and recommendations for hepatic monitoring.

EXPERT OPINION

We recommend laboratory testing of liver function tests prior to the administration of any oral antifungals, especially when clinically indicated. In the event of a first treatment failure, the diagnosis of onychomycosis must be confirmed, and consideration given to antifungal susceptibility testing. Antifungal stewardship will help reduce the incidence of antifungal resistance.

Voriconazole is superior to combined itraconazole/isotretinoin therapy and itraconazole monotherapy in recalcitrant dermatophytosis

BACKGROUND

There has been an emergence of recalcitrant, recurrent, and difficult-to-treat tinea. Monotherapy with oral antifungals leads to partial clearance or high recurrence of lesions. Isotretinoin is a good adjuvant to systemic antifungals in chronic dermatophytosis. Voriconazole could be a future alternative due to its efficacy against dermatophytes and little resistance.

OBJECTIVE

To evaluate the efficacy and safety of oral itraconazole, combined itraconazole/isotretinoin therapy, and voriconazole for recalcitrant tinea.

PATIENTS AND METHODS

This study included 90 patients with chronic, recurrent, and/or recalcitrant tinea. They were equally divided into 3 groups: itraconazole monotherapy, combined itraconazole/isotretinoin therapy, and voriconazole monotherapy. All patients received treatments for 6 weeks. The clinical response was classified as either a complete or incomplete clinical cure. Potassium hydroxide microscopy and culture were performed to identify mycological cure. Patients with complete cure were followed up for another 6 months to detect any recurrence.

RESULTS

Complete clinical cure was observed in 53.3% of the itraconazole group, 70% of the itraconazole/isotretinoin group, and 83.3% of the voriconazole group. Mycological cure was detected in 56.7% of the itraconazole group, 83.3% of the itraconazole/isotretinoin group, and 86.7% of the voriconazole group. There was a statistically significant difference between the three groups in favor of voriconazole, then the combined group. No significant adverse effects were observed. The recurrence rate was significantly lower in the voriconazole group compared to the other two groups.

CONCLUSIONS

Voriconazole could be a future alternative for the treatment of recalcitrant dermatophytosis.

Review of the alternative therapies for onychomycosis and superficial fungal infections: posaconazole, fosravuconazole, voriconazole, oteseconazole

Terbinafine and itraconazole are the most commonly used oral antifungals to treat onychomycosis and superficial dermatomycoses. Recently, poor response to oral terbinafine has been reported. We have summarized the most appropriate dosing regimens of posaconazole, fosravuconazole, voriconazole, and oteseconazole (VT-1161) to treat onychomycosis and superficial fungal infections. A structured search on PubMed and Google Scholar was conducted. Additionally, the bibliographies of selected articles were searched to identify relevant records. The number of records identified from the searches was 463, with 50 articles meeting the inclusion criteria for review. None of the new azoles are US FDA approved for onychomycosis treatment; however, an increasing number of studies have evaluated these agents. The efficacies (complete cure and mycologic cure) of the antifungal agents for dermatophyte great toenail onychomycosis treatment are terbinafine 250 mg/day × 12 weeks (Phase III trial) (38%, 70%), itraconazole 200 mg/day × 12 weeks (Phase III trial) (14%, 54%), posaconazole 200 mg/day × 24 weeks (Phase IIB) (54.1%, 70.3%), fosravuconazole 100 mg/day ravuconazole equivalent × 12 weeks (Phase III) (59.4%, 82.0%), and oteseconazole 300 mg/day loading dose × 2 weeks (Phase II), followed by 300 mg/week × 10 weeks (maintenance dose) (45%, 70%). Guidelines for monitoring are also presented.

A Paradigm Shift in the Treatment and Management of Onychomycosis

There is an increase in the incidence of onychomycosis, especially in at-risk populations. Onychomycosis is difficult to treat, as the efficacy of most antifungal agents is relatively low. Nondermatophyte molds (NDMs) and mixed infection (dermatophyte plus NDM) onychomycosis are contributing to growing antifungal resistance, as they are often underestimated and ignored due to incorrect diagnosis. There is a need for a paradigm shift in the management of onychomycosis to a patient-centered, holistic approach with an emphasis on laboratory diagnosis prior to initiating treatment, which enables the rational choice of the antifungal agent. Additionally, in the case of resistant infections, antifungal susceptibility testing is recommended. Strategies for effective management of onychomycosis include disinfection of fungal reservoirs in shoes and socks and prophylaxis posttreatment using topical antifungal agents. These measures may reduce the recurrence of onychomycosis and improve long-term clinical success.

Antifungal resistance in Superficial mycoses

BACKGROUND AND OBJECTIVE

With the widespread use of antifungals to treat superficial mycoses, reports of antifungal resistance are increasing. Antifungal resistance is becoming a public health challenge and needs to be addressed in parallel with antibacterial and antiviral resistance.

METHODS

We review the growing resistance of fungal pathogens such as Trichophyton species and the emergence of novel pathogens, including multidrug-resistant strains in superficial mycoses. We also discuss the importance of laboratory diagnosis and antifungal susceptibility testing (AFST) in the management of recalcitrant infections.

RESULTS AND CONCLUSION

Antifungal resistance can occur naturally or develop over time when fungi are exposed to antifungals. The frequency of terbinafine-resistant Trichophyton isolates is increasing. Opportunistic pathogens such as Aspergillus and Candida species have developed resistance to classic azoles such as itraconazole and fluconazole, and the newer azoles such as posaconazole and voriconazole. Although uncommon, topical antifungals such as efinaconazole and tavaborole have shown to induce resistance in Trichophyton rubrum. The emergence of multidrug-resistant Trichophyton mentagrophytes/interdigitale, Candida auris, and Aspergillus species causing severe infections is highly concerning. Routine AFST should be considered to determine the most effective treatment, especially if there is failure to therapy. Combination treatment of oral and topical antifungals may be a consideration for managing recalcitrant infections.

Evaluation of activity and toxicity of combining clioquinol with ciclopirox and terbinafine in alternative models of dermatophytosis

Dermatophytosis is a superficial fungal infection that affects humans and is very common in small animals. The treatment using the most commonly used antifungals is failing, and new therapeutic alternatives are required to combat the resistance of these fungal infections. Previous studies by the group have shown that clioquinol is an important therapeutic alternative in the treatment of dermatophytosis. The object was to conduct studies of antidermatophytic activity and the irritant potential from the double and triple combinations of clioquinol, terbinafine and ciclopirox in ex vivo and in vivo alternative models. To evaluate the irritant potential of antifungal combinations, the alternative HET-CAM method (chicken egg test chorioallantoic membrane) was used. Ex vivo models were used to assess the effectiveness of antifungal combinations, using pig hooves and veterinary fur. Any possible tissue damage was to assess through in histopathology of swine ears. HET-CAM results showed that all combinations can be classified as non-irritating, corroborated by the results of the histopathological evaluation of the pig's ear skin. Only the double combinations managed to remove 100% of the colony-forming units (CFU) formed on the pig's hooves. The clioquinol + terbinafine combination and the triple combination were more effective than clioquinol + ciclopirox in eradicating the preformed biofilm in fur of veterinary origin. These results show the potential of formulations of clioquinol in combination with antifungals for use in humans and in the veterinary field to combat dermatophytosis, as an important alternative therapy, for use in the near future.

The Growing Problem of Antifungal Resistance in Onychomycosis and Other Superficial Mycoses

Superficial mycoses are becoming increasingly resistant to current antifungal medications. As alternative therapeutic options are limited, the increasing frequency of reports of antifungal resistance is alarming. This epidemic parallels the rise of antibiotic resistance; however, the significance of this problem has yet to gain global attention. Here, we discuss the reports of antifungal resistance from around the world, present our own experience with treatment-resistant infections, and examine alternative treatment strategies. The majority of reports of recalcitrant infections indicate terbinafine resistance as the causative factor. Single-point mutations in the squalene oxidase gene is the most reported mechanism of resistance to terbinafine. Mixed infections of dermatophytes with non-dermatophyte molds and/or yeasts are becoming more prevalent and contributing to the resistant nature of these infections. The key to selecting an effective antifungal therapy for a recalcitrant infection is identification of the infectious organisms(s) and testing susceptibility of the organism(s) to antifungal drugs. Combination and sequential therapy regimens are options, but both require active monitoring for hepatic and renal function, drug interactions, and other adverse effects. Selected topical antifungals with a wide spectrum of activity may also be considerations in some clinical presentations. Innovative treatment regimens and novel therapeutics are needed to overcome the rising epidemic of antifungal resistance.