Tacrolimus, not triamcinolone acetonide, interacts synergistically with itraconazole, terbinafine, bifonazole, and amorolfine against clinical dermatophyte isolates

An update on the myriad antifungal resistance mechanisms in dermatophytes and the place of experimental and existential therapeutic agents for Trichophyton complex implicated in tinea corporis and cruris

INTRODUCTION

There is an epidemic emergence of increased resistance in dermatophytes with to antifungal drugs with ergosterol1 (Erg1) and Erg11 mutations to terbinafine and azoles. Apart from mutations, mechanisms that predict clinical failure include efflux pumps, cellular kinases, heat shock proteins (Hsp), and biofilms. Apart from itraconazole and SUBATM (Super-Bioavailable) itraconazole, measures that can be used in terbinafine failure include efflux-pump inhibitors, Hsp inhibitors and judicious use of antifungal drugs (topical + systemic) combinations.

AREAS COVERED

A PubMed search was done for the relevant studies and reviews published in the last 22 years using keywords dermatophytes OR Trichophyton, anti-fungal, resistance, mechanism and fungal AND resistance mechanisms. Our aim was to look for literature on prevalent species and we specifically researched studies on Trichophyton genus. We have analyzed varied antifungal drug mechanisms and detailed varied experimental and approved drugs to treat recalcitrant dermatophytosis.

EXPERT OPINION

Apart from administering drugs with low minimum inhibitory concentration, combinations of oral and topical antifungals (based on synergy data) and new formulations of existing drugs are useful in recalcitrant cases. There is a need for research into resistance mechanism of the existent Trichophyton strains in therapeutic failures in tinea corporis & cruris instead of data derived from laboratory strains which may not mirror clinical failures.

Augmenting Azoles with Drug Synergy to Expand the Antifungal Toolbox

Fungal infections impact the lives of at least 12 million people every year, killing over 1.5 million. Wide-spread use of fungicides and prophylactic antifungal therapy have driven resistance in many serious fungal pathogens, and there is an urgent need to expand the current antifungal arsenal. Recent research has focused on improving azoles, our most successful class of antifungals, by looking for synergistic interactions with secondary compounds. Synergists can co-operate with azoles by targeting steps in related pathways, or they may act on mechanisms related to resistance such as active efflux or on totally disparate pathways or processes. A variety of sources of potential synergists have been explored, including pre-existing antimicrobials, pharmaceuticals approved for other uses, bioactive natural compounds and phytochemicals, and novel synthetic compounds. Synergy can successfully widen the antifungal spectrum, decrease inhibitory dosages, reduce toxicity, and prevent the development of resistance. This review highlights the diversity of mechanisms that have been exploited for the purposes of azole synergy and demonstrates that synergy remains a promising approach for meeting the urgent need for novel antifungal strategies.

Antifungal Combinations in Dermatophytes

Dermatophytes are the most common cause of fungal infections worldwide, affecting millions of people annually. The emergence of resistance among dermatophytes along with the availability of antifungal susceptibility procedures suitable for testing antifungal agents against this group of fungi make the combinatorial approach particularly interesting to be investigated. Therefore, we reviewed the scientific literature concerning the antifungal combinations against dermatophytes. A literature search on the subject performed in PubMed yielded 68 publications: 37 articles referring to in vitro studies and 31 articles referring to case reports or clinical studies. In vitro studies involved over 400 clinical isolates of dermatophytes (69% Trichophyton spp., 29% Microsporum spp., and 2% Epidermophyton floccosum). Combinations included two antifungal agents or an antifungal agent plus another chemical compound including plant extracts or essential oils, calcineurin inhibitors, peptides, disinfectant agents, and others. In general, drug combinations yielded variable results spanning from synergism to indifference. Antagonism was rarely seen. In over 700 patients with documented dermatophyte infections, an antifungal combination approach could be evaluated. The most frequent combination included a systemic antifungal agent administered orally (i.e., terbinafine, griseofulvin, or azole-mainly itraconazole) plus a topical medication (i.e., azole, terbinafine, ciclopirox, amorolfine) for several weeks. Clinical results indicate that association of antifungal agents is effective, and it might be useful to accelerate the clinical and microbiological healing of a superficial infection. Antifungal combinations in dermatophytes have gained considerable scientific interest over the years and, in consideration of the interesting results available so far, it is desirable to continue the research in this field.

Severe onychomycosis management with oral terbinafine in a kidney transplantation setting: Clinical follow-up by image analysis

BACKGROUND

Severe onychomycosis treatment in kidney transplant recipients (KTR) is challenging because of drug interactions and adverse events. Tacrolimus remains the antirejection treatment (ART) of choice in kidney transplantation but tolerance with systemic terbinafine for the management of severe onychomycosis has not been studied.

OBJECTIVE

This study illustrates severe onychomycosis management in a kidney transplantation setting and investigates systemic terbinafine tolerance profile in KTR.

PATIENTS/METHODS

We retrospective analysed clinical data of KTR with a confirmed diagnosis of severe onychomycosis.

RESULTS

We retrieved a total of 29 KTR with severe onychomycosis needing an oral treatment to manage onychomycosis. In 55.1% (16/29) KTR, altered renal biological parameters or lack of guidelines to manage severe onychomycosis were the main reasons to deterring clinicians from prescribing oral treatments. 13 patients received an oral terbinafine treatment (9, 3 and 1 with a tacrolimus, cyclosporine and everolimus-based ART, respectively). Clinical and biological follow-up did not reveal severe drug interactions. ART blood levels showed significant variations in 2 patients without clinical consequences in renal graft. Two patients reported mild adverse events but after only one dose of terbinafine. Using an open-source image analysis program, clinical evolution of onychomycosis could be retrospectively quantified and followed up.

CONCLUSIONS

The results presented here suggest that oral terbinafine can be proposed to treat severe onychomycosis with an acceptable tolerance profile in KTR with different ART such as tacrolimus and highlight the need of multicentric studies to establish guidelines for onychomycosis treatment in KTR.