Dermatophytosis is a very common skin disorder and the most frequent infection encountered by practicing dermatologists. The identification, pathogenicity, biology, and epidemiology of dermatophytes, the causative agents of dermatophytosis, are of interest for both dermatologists and medical mycologists. Recent advances in molecular methods have provided new techniques for identifying dermatophytes, including intraspecies variations. Intraspecies subtyping and strain differentiation have made possible the tracking of infections, the identification of common sources of infections, recurrence or reinfection after treatment, and analysis of strain virulence and drug resistance. This review describes molecular methods of intraspecies subtyping and strain differentiation, including analyses of mitochondrial DNA and non-transcribed spacer regions of ribosomal RNA genes, random amplification of polymorphic DNA, and microsatellite markers, along with their advantages and limitations.
In follicular keratosis of the chin, keratotic follicular papules occur on the chin and jaw due to localized prolonged pressure and friction on the naked skin. We present one patient with this disorder. The dermatoscopic examination revealed many well-demarcated yellow spindle bodies in the patchy lesion. Therapy with 1.24R-dihydroxyvitamin D3 ointment was effective during the treatment but had no residual positive effect.
International Journal of Dermatology 2005, 44 , 765-768 765A 26-year-old woman with no family history of dermatophytosis presented with pruritic erythema on the right palm ( Fig. 1) in November 2002, 1 month after first noticing it. She had no lesions on the soles, toe webs, left palm, or nails. The erythema had been treated with topical steroids for 4 weeks, but had continued to expand. The erythema measured 42 mm × 36 mm, and was hyperemic and infiltrated unevenly. Its center showed no signs of healing, its periphery exhibited small vesicles, and its margin showed scales. On the scales, fungal hyphae and chains of arthroconidia were revealed by direct KOH test. The erythema was diagnosed as tinea manuum and was treated with topical terbinafine once daily. After several days of treatment, the erythema flared up and red papuloerythemas appeared on the back of both hands and on both forearms.Ten days after the first visit, the patient returned to our clinic for the treatment of newly developed eruptions. A trichophytin skin test produced an infiltrated erythema measuring 21 mm × 18 mm, confirming that the newly developed eruptions and exacerbated erythema on the right palm were due to a trichophytid reaction. Topical terbinafine was continued for the palm and fluocinolone acetonide ointment was applied on the newly developed eruptions on the arms from day 10 after the first visit. All the inflammatory eruptions subsided after 4 weeks of treatment and direct KOH test results were negative.The suspected cause of tinea manuum was the patient's pet female four-toed hedgehog ( Atelerix albiventris ) which she had kept for 4 years (Fig. 2). When she bought it from a local pet shop, it had desquamation on its body, but no lesions with loss of hair or quill and no dermatitis.The scaling decreased gradually with treatment given by a veterinarian.Three isolates of dermatophytes were obtained from the scale on the woman's palm (KMU 4455), scale removed from the hedgehog (KMU 4459-1), and a fallen-out quill (KMU 4459-2).KMU 4455 grew rapidly with an ivory-white and lightly powdery surface, and with concentric ripples at the periphery. The center of the colonies was fluffy and elevated slightly, with a yellow pigment beneath (Fig. 3). The strains from the hedgehog were morphologically similar to each other, and their colonies grew more slowly and had a more powdery texture than those of KMU 4455. KMU 4459-1 and KMU 4459-2 gave a positive urease test result, whereas KMU 4455 gave negative results even at day 7 of incubation. The microscopic findings of the three isolates were almost the same (Fig. 4). Numerous teardrop-shaped microconidia were produced along the sides of the rectangle of mycelium. Spherical microconidia clustered in some parts and some club-shaped, 2 -6-roomed macroconidia were observed. There were some poorly developed macroconidia and some elongated microconidia which were so large that they were intermediate in size between normal microconidia and macroconidia. There was no spiral body.The isolates were mate...
SUMMARY: Arthroderma benhamiae vectored by small animals, such as household pets, causes tinea lesions on human skin. The number of tinea cases caused by this species is increasing in Japan. We attempted to develop a simple molecular method for strain discrimination, which is expected to be useful in molecular epidemiology. Out of the 61 strains of A. benhamiae registered at our institute, 46 A. benhamiae strains showed very high degrees of sequence similarity on cluster analysis of the internal transcribed spacer regions of ribosomal RNA (rRNA) genes. These 46 strains, including 22 strains isolated from Japan, were further used for strain typing by analyzing the non-transcribed spacer (NTS) region of the rRNA gene. Polymerase chain reaction was performed using a primer pair designed for amplification of a part of the NTS region, and the amplicons were successfully discriminated by restriction fragment length polymorphism (RFLP) analysis performed using MvaI. RFLP analysis showed 11 NTS types (NTS1-NTS11) among the 46 strains. Out of the 22 Japanese strains, 10 were of the NTS8 type; 6, of the NTS1 type; 3, of the NTS2 type; and 3, of the NTS5 type. Molecular typing showed consistency of NTS types among the strains isolated from different lesions on the same patient, among the strains derived from the same family, and among the strains from pets and their owners. We observed that 3 out of the 4 NTS types among the Japanese strains were detected outside Japan as well.
To determine the relationships among Trichophyton species we constructed three phylogenies, based on the nucleotide sequences of the actin, rRNA and DNA topoisomerase II genes. These phylogenies showed several conflicting branch points. For example, strains of T. verrucosum, T. concentricum and T. mentagrophytes var. erinacei were mingled with strains of Arthroderma benhamiae and could not be separated into their own phylogenic groups. In addition, strains of A. vanbreuseghemii, T. tonsurans, T. mentagrophytes var. interdigitale and T. mentagrophytes var. quinckeanum were mingled with strains of A. simii and could not be separated into their own phylogenic groups. T. rubrum and T. violaceum made up a clade, which was phylogenetically related to the A. benhamiae clade or A. simii clade, depending on the gene examined. These findings indicate the need to reevaluate the boundaries among Trichophyton species using an alternative to morphological or molecular biological methods.
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