The epidemiology and etiology of onychomycosis in 2 laboratory centers affiliated to Tehran university of medical sciences during 2019-2020

Molecular identification and antifungal susceptibility profile of rare and emerging yeast species causing onychomycosis

OBJECTIVES

Onychomycosis is a nail infection caused by various fungal agents. In recent years, there has been an increase in cases of onychomycosis caused by rare fungi, which are often challenging to identify using conventional methods. Sometimes, these unusual species exhibit different antifungal susceptibility patterns compared to more common yeast species. Therefore, this study aimed to identify rare yeast species causing onychomycosis and assess their antifungal susceptibility profiles.

RESULTS

Nineteen rare and emerging yeast isolates, representing seven species, including Candida orthopsilosis (n = 9, 47.36%), Clavispora lusitaniae (formerly Candida lusitaniae) (n = 2, 10.52%), Wickerhamiella pararugosa (formerly Candida pararugosa) (n = 2, 10.52%), Naganishia diffluens (formerly Cryptococcus diffluens) (n = 2, 10.52%), Wickerhamomyces anomalus (n = 2, 10.52%), Cyberlindnera fabianii (n = 1, 5.26%), and Meyerozyma caribbica (formerly Candida fermentati) (n = 1, 5.26%), were identified. Most rare yeast agents exhibited high minimum inhibitory concentration (MIC) values for fluconazole.

A comprehensive review of nondermatophyte mould onychomycosis: Epidemiology, diagnosis and management

Nondermatophyte moulds (NDMs) are widely distributed and can be detected in association with mycotic nails; however, sometimes it can be challenging to establish the role of NDMs in the pathogenesis of onychomycosis (i.e. causative vs. contaminant). In studies where the ongoing invasive presence of NDMs is confirmed through repeat cultures, the global prevalence of NDMs in onychomycosis patients is estimated at 6.9% with the 3 most common genus being: Aspergillus, Scopulariopsis and Fusarium. NDM onychomycosis can, in many cases, appear clinically indistinguishable from dermatophyte onychomycosis. Clinical features suggestive of NDMs include proximal subungual onychomycosis with paronychia associated with Aspergillus spp., Fusarium spp. and Scopulariopsis brevicaulis, as well as superficial white onychomycosis in a deep and diffused pattern associated with Aspergillus and Fusarium. Longitudinal streaks seen in patients with distal and lateral onychomycosis may serve as an additional indicator. For diagnosis, light microscopic examination should demonstrate fungal filaments consistent with an NDM with at least two independent isolations in the absence of a dermatophyte; the advent of molecular testing combined with histological assessment may serve as an alternative with improved sensitivity and turnover time. In most instances, antifungal susceptibility testing has limited value. Information on effective treatments for NDM onychomycosis is relatively scarce, unlike the situation in the study of dermatophyte onychomycosis. Terbinafine and itraconazole therapy (continuous and pulsed) appear effective to varying extents for treating onychomycosis caused by Aspergillus, Fusarium or Scopulariopsis. There is scant literature on oral treatments for Neoscytalidium.

Novel and Investigational Treatments for Onychomycosis

Onychomycosis is a common nail disease caused by fungi. The primary pathogens are dermatophytes; however, yeasts, non-dermatophyte moulds, and mixed fungal populations may also contribute to the development of a recalcitrant condition, usually accompanied by difficulties in everyday life and severe emotional stress. Treatment failure and relapse of the infection are the most frequent problems, though new issues have become the new challenges in the therapeutic approach to onychomycosis. Resistance to antifungals, an increasing number of comorbidities, and polydrug use among the ageing population are imperatives that impose a shift to safer drugs. Topical antifungals are considered less toxic and minimally interact with other drugs. The development of new topical drugs for onychomycosis is driven by the unmet need for effective agents with prolonged post-treatment disease-free time and a lack of systemic impact on the patients’ health. Efinaconazole, Tavaborole, and Luliconazole have been added to physicians’ weaponry during the last decade, though launched on the market of a limited number of countries. The pipeline is either developing new products (e.g., ME-1111 and NP213) with an appealing combination of pharmacokinetic, efficacy, and safety properties or reformulating old, well-known drugs (Terbinafine and Amphotericin B) by using new excipients as penetration enhancers.