Prevalence and risk factors for onychomycosis in acute care dermatology wards

We conducted a cross-sectional study on the clinical and mycological features of onychomycosis in patients in the dermatology ward of Iwate Medical University Hospital, an acute care hospital. Of the 226 hospitalized patients, 73 (32.3%) had onychomycosis and 61 (26.9%) were diagnosed after admission. The toenail was the most common site of onychomycosis (94.5%), while toenail plus fingernail and fingernail only sites were 4.1% and 1.4%, respectively. The most common clinical form of onychomycosis was distal and lateral subungual onychomycosis (79%) with Trichophyton rubrum (66.7%) and T. interdigitale (27.8%) as the main causative species. Patients who were older, or had neurological diseases, or needed stretcher transfer had onychomycosis significantly more frequently than those who were obese, had diabetes, cancer, needed an escort for moving, or could move independently. Our study suggests that there is likely to be a significant number of untreated and undiagnosed patients with onychomycosis in acute care hospitals. Therefore, it is necessary to increase awareness of onychomycosis in hospitals.

Deep dermatophytosis caused by Trichophyton rubrum in an elderly patient with CARD9 deficiency: A case report and literature review

Deep dermatophytosis is an invasive and sometimes life-threatening fungal infection mainly reported in immunocompromised patients. However, a caspase recruitment domain-containing protein 9 (CARD9) deficiency has recently been reported to cause deep dermatophytosis. Herein, we report the first Japanese case of deep dermatophytosis associated with CARD9 deficiency. An 80-year-old Japanese man with tinea corporis presented with subcutaneous nodules on his left sole. Histopathological findings revealed marked epithelioid cell granulomas with filamentous fungal structures in the deep dermis and subcutis, and the patient was diagnosed with deep dermatophytosis. Despite antifungal therapy, the subcutaneous nodule on his left sole gradually enlarged, his left calcaneal bone was invaded, and the patient finally underwent amputation of his left leg. Genetic analysis revealed a homozygous CARD9 c.586 A > G (p. Lys196Glu) variant, suggesting a CARD9 deficiency. Here, we discuss the clinical features of CARD9 deficiency-associated deep dermatophytosis with a case report and review of the literature.

Rose bengal-encapsulated chitosan nanoparticles for the photodynamic treatment of Trichophyton species

Rose bengal (RB) solutions coupled with a green laser have proven to be efficient in clearing resilient nail infections caused by Trichophyton rubrum in a human pilot study and in extensive in vitro experiments. Nonetheless, the RB solution can become diluted or dispersed over the tissue and prevented from penetrating the nail plate to reach the subungual area where fungal infection proliferates. Nanoparticles carrying RB can mitigate the problem of dilution and are reported to effectively penetrate through the nail. For this reason, we have synthesized RB-encapsulated chitosan nanoparticles with a peak distribution size of ~200 nm and high reactive oxygen species (ROS) production. The RB-encapsulated chitosan nanoparticles aPDT were shown to kill more than 99% of T. rubrum, T. mentagrophytes, and T. interdigitale spores, which are the common clinically relevant pathogens in onychomycosis. These nanoparticles are not cytotoxic against human fibroblasts, which promotes their safe application in clinical translation.

Epidemiological study of antifungal-resistant dermatophytes isolated from Japanese patients

An epidemiological study of antifungal drug-resistant dermatophytes was conducted as a follow-up to our 2020 survey. Dermatophytes were isolated in 2022 from the same dermatology clinics as in the previous study. In total, 288 Trichophyton interdigitale and Trichophyton rubrum clinical isolates were obtained from 288 human cases of dermatophytosis in Tokyo, Saitama, Shizuoka, and Kumamoto, Japan. Four strains were found to be resistant to terbinafine (TRF) and susceptible to itraconazole (ITZ), luliconazole (LCZ), and ravuconazole (RVZ), and three other strains were found to be resistant to ITZ and susceptible to TRF, LCZ, and RVZ. We determined the sequences of the squalene epoxidase (SQLE)-encoding gene in the three TRF-resistant T. rubrum strains, and found that two strains harbored L393F missense mutations, and one strain harbored a F397L missense mutation. The results of the present study indicated that the prevalence of TRF-resistant dermatophytes has not increased since 2020. However, TRF-resistant T. interdigitale (L393F mutation) was isolated for the first time, indicating that attention should be paid to the presence of TRF-resistant T. interdigitale in the future. We also examined for the first time the epidemiology of ITZ-resistant T. rubrum in Japanese patients. Although the number of ITZ-resistant strains was not large, the results confirmed that ITZ-resistant T. rubrum strains do exist in Japanese patients.

Itraconazole resistance of Trichophyton rubrum mediated by the ABC transporter TruMDR2

BACKGROUND

Dermatophytes showing reduced sensitivity to antifungal agents have emerged in several countries. One terbinafine resistant strain of Trichophyton rubrum, TIMM20092, also showed reduced sensitivity to itraconazole (ITC) and voriconazole (VRC). The expression of two genes (TruMDR2 and TruMDR3) encoding multidrug transporters of the ABC family was found to be highly up-regulated in this strain. Deletion of TruMDR3 in TIMM20092 abolished its resistance to VRC but only slightly reduced its resistance to ITC.

OBJECTIVES

We examined the potential of T rubrum to develop resistance to ITC by analysing the mechanism of ITC resistance in TIMM20092.

METHODS

The deletion of TruMDR2 by gene replacement was performed in TIMM20092 and one TruMDR3-lacking mutant (∆TruMDR3) previously generated from TIMM20092. TruMDR2 single and TruMDR2/TruMDR3 double mutants (∆TruMDR2 and ∆TruMDR2/3) were successfully obtained, respectively.

RESULTS

The suppression of TruMDR2 was shown to abolish resistance to ITC in TIMM20092 and the TruMDR3-lacking mutant, strongly suggesting that TruMDR2 is a major contributor to ITC resistance in TIMM20092.

CONCLUSIONS

Our study highlights the possible role of the ABC transporter TruMDR2 in ITC resistance of T. rubrum.

Validation of a lateral flow immunochromatographic assay for tinea unguium diagnosis

Tinea unguium is a common nail disease caused by dermatophytes. Although direct potassium hydroxide (KOH) microscopy and fungal culture are considered the gold standard for diagnosing this disease, their accuracy is insufficient. A lateral flow immunochromatographic assay (LFIA) kit, using a monoclonal antibody against Trichophyton rubrum, was developed and its sensitivity was recently improved 50% in vitro relative to its earlier version. The present study aimed to validate the clinical utility of this improved LFIA kit for diagnosing tinea unguium in comparison with direct KOH microscopy. A similar trial was simultaneously performed using scale samples from patients with tinea pedis to determine the assay's diagnostic potential. Nail samples, approximately 2 mg in weight, were collected from 112 non-treated tinea unguium patients and 56 non-tinea unguium patients. Samples from 25 tinea pedis patients and 20 non-tinea pedis patients were also collected. The sensitivity and specificity of the LFIA kit for tinea unguium was 84.8% (95/112) (95% confidence interval [CI], 76.8-90.9) and 83.9% (47/56) (95% CI, 71.7-92.4), respectively. The inconsistency rate was 15.5% (26/168) (95% CI, 10.4-21.9). The sensitivity and specificity of the LFIA kit for tinea pedis was 84.0% (21/25) and 100.0% (20/20), respectively. These results suggest that for diagnosing tinea unguium, the LFIA kit is a useful supplement to, but not a replacement for, direct KOH microscopy. For definitive diagnosis of suspected cases, appropriate sampling, repeated examinations, and a combination of diagnostic techniques are essential.

Genotyping of Russian isolates of fungal pathogen Trichophyton rubrum, based on simple sequence repeat and single nucleotide polymorphism

BACKGROUND

The Trichophyton rubrum species group consists of prevalent causative agents of human skin, nail and hair infections, including T rubrum sensu stricto and T violaceum, as well as other less well-established or debatable taxa like T soudanense, T kuryangei and T megninii. Our previous study provided limited evidence in favour of the existence of two genetic lineages in the Russian T rubrum sensu stricto population.

OBJECTIVES

We aimed to study the genetic structure of the Russian population of T rubrum and to identify factors shaping this structure.

METHODS

We analysed the polymorphism of 12 simple sequence repeat (SSR or microsatellite) markers and single nucleotide polymorphism in the TERG_02941 protein-coding gene in 70 T rubrum isolates and performed a phylogenomic reconstruction.

RESULTS

All three types of data provided conclusive evidence that the population consists of two genetic lineages. Clustering, performed by means of microsatellite length polymorphism analysis, was strongly dependent on the number of nucleotide repeats in the 5'-area of the fructose-1,6-bisphosphate aldolase gene. Analysis of molecular variance (AMOVA) on the basis of SSR typing data indicated that 22%-48% of the variability was among groups within T rubrum. There was no clear connection of population structure with types of infection, places of geographic origin, aldolase gene expression or urease activity.

CONCLUSION

Our results suggest that the Russian population of T rubrum consists of two cosmopolitan genetic lineages.

Evaluation of the photodynamic efficacy and effects of haematoporphyrin monomethyl ether on Trichophyton rubrum microconidia in vitro

BACKGROUND

Current available treatment modes against dermatophytoses are often tedious and sometimes unsatisfactory. As an emerging and promising approach, antimicrobial photodynamic therapy (aPDT) attracts much attention in the treatment of superficial or localised infections.

OBJECTIVES

This work investigated the photodynamic efficacy and effects of haematoporphyrin monomethyl ether (HMME) on microconidia of Trichophyton rubrum in vitro.

METHODS

The photodynamic killing efficacy of HMME on microconidia of two T rubrum strains was assessed by MTT assay. The effects of HMME-mediated aPDT on the growth of T rubrum and cellular structure of microconidia were also investigated. Confocal laser scanning microscopy (CLSM) and flow cytometry were employed to study the intracellular localisation of HMME and generation of reactive oxygen species (ROS).

RESULTS

HMME showed no obvious toxicity in the dark, but after light irradiation it inactivated the T rubrum microconidia in a light energy dose-dependent manner, and inhibited the growth of T rubrum. CLSM demonstrated that HMME initially bound to the cell envelop and entered into the cell after light irradiation. HMME-mediated aPDT also damaged the cell cytoplasm and increased the accumulation of intracellular ROS, resulting in cell death.

CONCLUSIONS

The results suggested that HMME-mediated aPDT had potential to be used in the treatment of superficial infections caused by T rubrum.

Piper regnellii extract biopolymer-based microparticles: production, characterization and antifungal activity

AIMS

This study aims to improve characteristics of Piper regnellii extract to make it applicable in formulations to treat dermatophytosis, also known as ringworm.

METHODS AND RESULTS

Microparticles (MPs) were produced by spray drying with gelatin, alginate and chitosan as encapsulating agents; characterized by scanning electron microscopy, encapsulation efficiency, thermal analyses and X-ray diffraction; and tested against Trichophyton rubrum by broth microdilution. Produced MPs had a mean diameter less than 2 μm, an increase in stability and release of the extract and good results for encapsulation efficiency, being 85·6% to gelatin MP, 71·3% to chitosan MP and 60·6% to alginate. MPs preserved the antifungal activity of P. regnellii extract T. rubrum.

CONCLUSION

Microencapsulation provided a significant improvement in the stability of the P. regnellii extract and better solubilization of chemical compounds, maintaining the antifungal effect against T. rubrum.

SIGNIFICANCE AND IMPACT OF THE STUDY

These results are useful for developing a formulation to treat fungal infections caused by dermatophyte species.