Antifungal susceptibility patterns of yeasts and filamentous fungi isolated from nail infection

Onychomycosis due to Fusarium species in different continents, literature review on diagnosis and treatment

Fusarium species are an emerging cause of onychomycosis, and the number of cases has dramatically increased in recent decades worldwide. This review presents an overview of the onychomycosis cases caused by Fusarium species and diagnosis and treatment that have been reported in the literature. The most common causative agent of onychomycosis is F. solani species complex, which accounts for 11.68% of the cases of Fusarium onychomycosis, followed by the F. oxysporum species complex (164 out of 1669), which is accounted for 9.83% of the total. F. fujikuroi species complex (42 out of 1669) and F. dimerum species complex (7 out of 1669) are responsible for 2.52% and 0.42 cases, respectively. Fusarium nail infections were reported in patients aged range 1-98, accounting for 5.55% (1669 out of 30082) of all cases. Asia has the highest species diversity of Fusarium onychomycosis (31.51%). South America accounts for 21.09%, and the most common causative agent is F. solani (19.32%), followed by F. oxysporum species complex (15.63%). Europe accounts for 4.90% of cases caused by F. oxysporum, followed by F. solani. Africa accounts for 23.87% of the cases due to the F. solani species complex, followed by F. oxysporum and F. fujikuroi. Distal and lateral subungual onychomycosis was the most common clinical symptom accounting for 58.7% (135 out of 230) of the cases. Data analysis relieved that terbinafine and itraconazole are active treatments for Fusarium onychomycosis. For a definitive diagnosis, combining of direct examination, culture and sequencing of the elongation factor of translation 1α are recommended. Accurate identification of the causative agents of onychomycosis due to Fusarium species and antifungal susceptibility testing is essential in patient management.

Population differentiation, antifungal susceptibility, and host range of Trichophyton mentagrophytes isolates causing recalcitrant infections in humans and animals

The major problems in determining the causative factors of the high prevalence of dermatophytoses include the lack of a well-standardized antifungal susceptibility testing method, the low consistency of in vitro and clinical minimal inhibitory concentration values, the high genomic diversity of the population, and the unclear mechanism of pathogenicity. These factors are of particular importance when the disease is recalcitrant and relapses. Herein, we identified and characterized Trichophyton mentagrophytes isolates obtained from therapy-resistant cases in humans and animals. We used genomic diversity analysis of 17 human and 27 animal clinical isolates with the MP-PCR technique, determined their phenotypic enzymatic activity and host range, and performed antifungal susceptibility testing to currently available antifungal drugs from various chemical groups. Genomic diversity values of 35.3% and 33.3% were obtained for clinical isolates from humans and animals, respectively, yet without any relationship to the host species or antifungal drug to which resistance in therapy was revealed. The highest activity of keratinase enzymes was recorded for fox, guinea pig, and human hairs. These hosts can be considered as the main species in the host range of these isolates. A phenyl morpholine derivative, i.e. amorolfine, exhibited superior activity against strains obtained from both humans and animals with the lowest MIC₅₀. Interestingly, high compliance of terbinafine in vitro resistance with clinical problems in the treatment with this substance was shown as well. The high resistance of dermatophytes to drugs is the main cause of the recalcitrance of the infection, whereas the other features of the fungus are less important.

MIC and Upper Limit of Wild-Type Distribution for 13 Antifungal Agents against a Trichophyton mentagrophytes-Trichophyton interdigitale Complex of Indian Origin

Dermatophytosis due to the Trichophyton mentagrophytes-Trichophyton interdigitale complex is being increasingly reported across India. Reports of therapeutic failure have surfaced recently, but there are no clinical break points (CBP) or epidemiological cutoffs (ECVs) available to guide the treatment of dermatophytosis. In this study, a total of 498 isolates of the T. mentagrophytes -interdigitale complex were collected from six medical centers over a period of five years (2014 to 2018). Antifungal susceptibility testing of the isolates was carried out for itraconazole, fluconazole, ketoconazole, voriconazole, luliconazole, sertaconazole, miconazole, clotrimazole, terbinafine, amorolfine, naftifine, ciclopirox olamine, and griseofulvin. The MICs (in mg/liter) comprising >95% of the modeled populations were as follows: 0.06 for miconazole, luliconazole, and amorolfine; 0.25 for voriconazole; 0.5 for itraconazole, ketoconazole, and ciclopirox olamine; 1 for clotrimazole and sertaconazole; 8 for terbinafine; 16 for naftifine; 32 for fluconazole; and 64 for griseofulvin. A high percentage of isolates above the upper limit of the wild-type MIC (UL-WT) were observed for miconazole (29%), luliconazole (13.9%), terbinafine (11.4%), naftifine (5.2%), and voriconazole (4.8%), while they were low for itraconazole (0.2%). Since the MICs of itraconazole were low against the T. mentagrophytes -interdigitale complex, this could be considered the choice of first-line treatment. The F397L mutation in the squalene epoxidase (SE) gene was observed in 77.1% of isolates with a terbinafine MIC of ≥1 mg/liter, but no mutation was detected in isolates with a terbinafine MIC of <1 mg/liter. In the absence of CBPs, evaluation of the UL-WT may be beneficial for managing dermatophytosis and monitoring the emergence of isolates with reduced susceptibility.

Comparison of the in vitro activities of newer triazoles and established antifungal agents against Trichophyton rubrum

One hundred eleven clinical Trichophyton rubrum isolates were tested against 7 antifungal agents. The geometric mean MICs of all isolates were, in increasing order: terbinafine, 0.03 mg/liter; voriconazole, 0.05 mg/liter; posaconazole, 0.11 mg/liter; isavuconazole, 0.13 mg/liter; itraconazole, 0.26 mg/liter; griseofulvin, 1.65 mg/liter; and fluconazole, 2.12 mg/liter.

Luliconazole demonstrates potent in vitro activity against dermatophytes recovered from patients with onychomycosis

The in vitro activities of luliconazole, amorolfine, ciclopirox, and terbinafine were determined against 320 dermatophyte isolates from large toenails of onychomycosis patients enrolled into an ongoing phase 2b/3 clinical study. The geometric mean MIC for luliconazole was 0.00022 μg/ml against all isolates, compared to 0.0194 to 0.3107 μg/ml for the three other agents. The in vitro potency of luliconazole was maintained regardless of the dermatophyte species.