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Fungal Infections
Published in Ayşe Serap Karadağ, Lawrence Charles Parish, Jordan V. Wang, Roxburgh's Common Skin Diseases, 2022
Uwe Wollina, Pietro Nenoff, Shyam Verma, Uta-Christina Hipler
Clinical presentation: This is highly variable depending on the fungal species and immune status of the host. Zoophilic Microsporum canis and anthropophilic T. tonsurans are the most common species. The infection of the hair shaft can be either ectothrix (M. canis and M. audouinii), which fluoresce with the Wood’s light, or endothrix (T. tonsurans, T. violaceum, T. soudanense). In the latter case, the hair cuticle remains intact, but the inner part is filled with spores leading to the black-dot ringworm appearance on dermatoscopy. A moth-eaten pattern can be caused by M. audouinii or T. violaceum. Endothrix infections are less immunogenic and sometimes asymptomatic. Scaling may be psoriasiform.
Aetiology and Laboratory Diagnosis
Published in Raimo E Suhonen, Rodney P R Dawber, David H Ellis, Fungal Infections of the Skin, Hair and Nails, 2020
Raimo E Suhonen, Rodney P R Dawber, David H Ellis
Microsporum audouinii is an anthropophilic fungus causing non-inflammatory infections of the scalp and skin, especially in children. Once the cause of epidemics of tinea capitis in Europe and North America, this is now becoming less frequent. Invaded hairs show an ectothrix infection and usually fluoresce a bright greenish-yellow under Wood’s ultraviolet light. Key features include the absence of conidia, poor or absence of growth on polished rice grains, inability to perforate hair in vitro and culture characteristics.
Dermatophytes
Published in Rossana de Aguiar Cordeiro, Pocket Guide to Mycological Diagnosis, 2019
Germana Costa Paixão, Marcos Fábio Gadelha Rocha, Débora de Souza Colares Maia Castelo-Branco, Raimunda Sâmia Nogueira Brilhante, José Júlio Costa Sidrim
Direct examination reveals ectothrix infection, similar to M. canis. It grows slowly on Sabouraud agar, yielding two colony types: one has a characteristically glabrous and grooved appearance and an elevation in the center, with orange to rust color, which quickly fades when maintained in the laboratory. The other colony type is flat and white, with a leathery texture.
Strategies to improve the diagnosis and clinical treatment of dermatophyte infections
Published in Expert Review of Anti-infective Therapy, 2023
Trichophyton species are generally more sensitive to terbinafine, while Microsporum species are more sensitive to griseofulvin. Although primarily recommended for the treatment of Microsporum species that cause ectothrix-type tinea capitis, griseofulvin is unavailable in many countries worldwide [46]. In a lack of griseofulvin, new treatment approaches have been proposed for patients with tinea capitis [47]. Treatment-resistant dermatophytosis caused by T. rubrum, T. interdigitale, and T. mentagrophytes genotype VIII (T. indotineae) has emerged as a public health issue worldwide, whereas the latter has gained importance in endemic regions (e.g. India) and has spread to Europe [32–34,48,49] and the Middle East [50–52]. Most dermatophyte resistance has been reported with regard to terbinafine and is characterized by point mutations in the squalene epoxidase gene [53,54]. Furthermore, resistance to azoles has been reported infrequently until now, but mostly together with allylamine resistance [44,45].