Dermatophytes: Biology, Diseases, and Morphology PDF

Biology of and diseases caused by Dermatophytes by: The Power Puffballs Dermatophytes Etiologic agents of skin infections called “ringworm” or tinea Responsible for superficial and cutaneous mycoses  Dermatophytes Unifying Characteristics 1. Taxonomy Ph...

Biology of and diseases caused by Dermatophytes by: The Power Puffballs Dermatophytes Etiologic agents of skin infections called “ringworm” or tinea Responsible for superficial and cutaneous mycoses  Dermatophytes Unifying Characteristics 1. Taxonomy Phylum Ascomycota Class Eurotiomycetes Order Onygenales Family Arthrodermataceae Figure 1. Phylogenetic tree showing the major genera of the family Arthrodermataceae. Reprinted from Graeser and Saunte (2020)  Dermatophytes Unifying Characteristics 1. Taxonomy 2. Morphology Figure 2. Colony morphologies of selected Dermatophyte species. Reprinted from Biomed Colonies: Diagnostics (n.d.) Powdery, velvety, cottony, or fluffy and of varying colors depending on the species. Microscopic Characteristics: Septate hyphae Macroconidia Microconidia Specialized Structures: Chlamydoconidia Spiral hyphae Figure 3. Microscopic characteristics of most clinically important dermatophytes. Reprinted from Monteiro (2021). (A) Trichophyton rubrum. (B) Trichophyton mentagrophytes. (C) Trichophyton tonsurans. (D) Epydermophyton floccosum. (E) Microsporum canis. (F) Nannizzia gypsea.  Dermatophytes Unifying Characteristics 1. Taxonomy 2. Morphology 3. Keratinophilic nature Virulence factor: Keratinase Figure 4. Pathogenesis of invasive dermatophytosis. Reprinted from Coelho et al. (2024)  Dermatophytes Unifying Characteristics 1. Taxonomy 2. Morphology 3. Keratinophilic nature 4. Genome Genome size: 2.25 Mb to 24.1 Mb Ploidy: Haploid (Conidia: Uninucleated; Hyphae: Multinucleated) Genomic conservation: The genome is conserved with over 6000 orthologs Figure 5. Mitochondrial genomes of Trichophyton rubrum and T. violaceum. Reprinted from Achterman (2012).  Dermatophytes Unifying Characteristics 1. Taxonomy 2. Morphology 3. Keratinophilic nature 4. Genome 5. Habitat Anthropophilic - live on humans Zoophilic - live on animals Geophililic - live in the environment Figure 6. Ecological classification of Dermatophytes. Reprinted from Tang et al (2024).  Dermatophytes Growth Rate: E. floccosum colonies are generally slow-growing. Colony Appearance: Color: Greenish-brown or khaki. Texture: Suede-like surface, with a raised, folded center and a flat, fringed periphery. Aging: Older colonies may develop white, pleomorphic tufts of mycelium. Reverse Pigment: Colonies often display a yellowish-brown pigment on the reverse side. Figure 1. Culture of E. floccosum Epidermophyton Epidermophyton flocossum Known to cause a range of fungal infections: Unlike other dermatophytes, E. An anthropophilic Tinea pedis (athlete’s foot) floccosum does not dermatophyte with Tinea cruris (jock itch) invade hair in vivo and worldwide distribution Tinea corporis (ringworm) has no specific growth Onychomycosis (nail requirements. infections)  Morphological Description Cultural Characteristics Growth Rate: E. floccosum colonies are generally slow-growing. Colony Appearance: Color: Greenish-brown or khaki. Texture: Suede-like surface, with a raised, folded center and a flat, fringed periphery. Aging: Older colonies may develop white, pleomorphic tufts of mycelium. Reverse Pigment: Colonies often display a yellowish-brown pigment on the reverse side. Figure 1. Culture of E. floccosum  Morphological Description Microscopic Characteristics Key Microscopic Features Macroconidia: Smooth, thick-walled structures. Typically clustered, growing directly from hyphae. Chlamydospores: Formed in older cultures. Serve as survival structures, helping the organism withstand adverse conditions. Microconidia: Not produced by E. floccosum, Figure 2. Macroconidia and chlamydoconidia of E. floccosum. differentiating it from other dermatophytes.  A Case of Inflammatory Tinea Corporis by Epidermophyton floccosum A 49-year-old woman presented with nail lesions on both feet, primarily affecting the left big toe, which showed mild inflammation and thickening of the nail bed. She had no major health issues, but prolonged use of closed shoes was noted as a significant risk factor. Family history revealed no similar conditions. To diagnose, scales from the affected nail were scraped and treated with 20% potassium hydroxide (KOH) for microscopic examination. Samples were also cultured on Sabouraud dextrose agar with chloramphenicol and cycloheximide, incubated at 28–30 °C for 15 days. The culture developed beige, velvety colonies, with microscopic analysis revealing septate Figure 3. (A) E. floccosum-induced tinea unguium. hyphae, club-shaped macroconidia with thick walls, and no microconidia, (B) Direct examination with 20% KOH (C) E. floccosum on potato dextrose agar. On the right confirming Epidermophyton floccosum. side of Figure 3.C, the generation of yellow pigment is visible. (D) Microcultures stained with Treatment included topical antifungals (8% ciclopirox, 5% amorolfine, and lactophenol cotton blue. The white arrow shows the chlamydoconidium. The black arrow shows the 10% efinaconazole) and daily oral terbinafine at 250 mg as first-line macroconidium. therapy. (Zúniga et al., 2023) Microsporum Morphological Description Cultural Characteristics Figure 4. Microsporum spp. cultures (The University of Adelaide, n.d.) Colony Appearance: Color: yellowish to brownish Texture: granular to cottony surface Reverse Pigment: cream-coloured or brown colony  Morphological Description Microscopic Characteristics Key Microscopic Features If present, both macro- and microconidia are hyaline Macroconidia: multiseptate, with thick rough cell walls clavate, fusiform or spindle-shaped. Microconidia: single-celled, with smooth cell walls predominantly clavate in shape Figure 5. Macroconidia of M. canis (The University of Adelaide, n.d.)  Case Study: Tinea corporis caused by Microsporum canis A 25-year-old woman presented to the dermatology clinic with a progressive 2-week history of increasingly itchy rashes involving all regions of her body anteriorly and posteriorly. Skin lesions had developed 10 days after the adoption of a 2-month- old male blue cat; similar lesions were seen on her parents. Physical examination revealed numerous annular erythematous plaques across her entire body but particularly on the face, neck, upper limbs and trunk (Figure 6a). Direct microscopic examination was positive, and all fungal cultures grew colonies of Microsporum canis (Figure 6c). Random amplified polymorphic DNA (RAPD), using primer OPK 20, showed that the five isolated strains were the same fungal species Figure 6. (a) Extensive tinea corporis. (b) Patchy alopecia on the head of cat. (c) Slide culture of M. (Figure 6d). canis on potato dextrose agar at 25°C on day 7 (lactic acid cotton-blue staining × 400). (d) The pattern of RAPD with primer OPK 20. (Xia, 2022)  Case Study: Family outbreak of Tinea corporis caused by Microsporum canis Treated with itraconazole (200 mg/d) for 1 month. 3 months after the completion of treatment, the lesions had resolved. Skin lesions of other patients and pets have also been cured by topical therapy. Figure 7. (a) Extensive tinea corporis. (b) Patchy alopecia on the head of cat. (Xia, 2022) Notes on M. canis infection: often associated with exposure to symptomatic or asymptomatic cats or dogs usually produces inflammatory, eczematous lesions with erythema and scaling. Trichophyton Morphological Description Cultural Characteristics Figure 8. Trichophyton spp. cultures (The University of Adelaide, n.d.) Colony Appearance: Color: white to cream Texture: powdery to granular surface Reverse Pigment: yellow-brown to reddish-brown  Morphological Description Microscopic Characteristics Key Microscopic Features both smooth-walled macro- and microconidia Macroconidia: thin- or thick-walled, clavate to fusiform borne laterally directly on the hyphae or on short pedicels few or absent in many species Microconidia: Figure 9. Trichophyton sp. spherical, pyriform to clavate or of irregular shape Note: The presence of microconidia differentiates this genus from Epidermophyton, and the smooth-walled, mostly sessile macroconidia differentiates it from Lophophyton, Microsporum, Nannizzia, and Paraphyton.  Case Study: Tinea Faciei Caused by Trichophyton benhamiae A 4-year-old girl from China developed an itchy, erythematous, and annular plaque on her right face for the past 2 months. She was in close contact with the fur of a fox for almost 1 week. Septate hyaline hyphae were detected by direct mycological examination of the scales. Figure 10. (a) and (b) Culture on SDA at 26 °C after 2 Cultures grew on Sabouraud’s dextrose agar weeks yielded white colonies, peripherally radiating, centrally raised, and powdery margins. The reverse side showed yellow to brown colonies. (c) Lactophenol (SDA) at 26 °C for 2 weeks revealed the cotton blue stain revealed filamentous and spiral hyphae (original magnification ✕ 200). (d) Lactophenol presence of T. mentagrophytes. cotton blue stain revealed a grape-like arrangement of microconidia laterally and terminally inserting at the hyphae (original magnification ✕ 200) (Tan et al. 2020).  Case Study: Tinea Faciei Caused by Trichophyton benhamiae A molecular sequencing test confirmed that the isolate was consistent with reference strains to T. benhamiae. Then, the diagnosis of tinea faciei due to T. benhamiae was made. Treatment with terbinafine (oral 125 mg/d) and sertaconazole nitrate cream (topical, twice daily) Figure 11. (a) Annular plaque with erythema covered for 4 weeks was initiated and achieved with scales and crusts (3 cm × 5 cm) on the right face. (b) Complete resolution of the plaque with residual significant improvement of the skin lesions. erythema after 4 weeks of treatment with terbinafine (oral, 125 mg/d) (Tan et al. 2020). (Tan et al. 2020)  REFERENCES Grumbt, M., Monod, M., Yamada, T., Hertweck, C., Kunert, J., & Staib, P. (2013). Keratin degradation by dermatophytes relies on cysteine dioxygenase and a sulfite efflux pump. Journal of Investigative Dermatology, 133(6), 1550–1555. https://doi.org/10.1038/jid.2013.41 Monod, M., & Lanternier, F. (2022). Dermatophytes and dermatophytosis. In Elsevier eBooks (pp. 397–407). https://doi.org/10.1016/b978-0-12-818731-9.00231-77-z Moskaluk, A. E., & VandeWoude, S. (2022). Current Topics in Dermatophyte Classification and Clinical Diagnosis. Pathogens, 11(9), 957. https://doi.org/10.3390/pathogens11090957 Tan, J., Liu, X., Gao, Z., Yang, H., Yang, L., & Wen, H. (2020). A case of Tinea Faciei caused by Trichophyton benhamiae: first report in China. BMC Infectious Diseases, 20(1). https://doi.org/10.1186/s12879-020-4897-z The University of Adelaide. (n.d.). Dermatophytes. Retrieved November 04, 2024, from https://www.adelaide.edu.au/mycology/fungal-descriptions-and-antifungal-susceptibility/dermatophytes Xia, X. (2022). Family outbreak of Microsporum canis infection. QJM: An International Journal of Medicine, 115(10), 679–680. https://doi.org/10.1093/qjmed/hcac170 Zúniga, B., Arita-Ramos, M., Acevedo-Almendárez, L., García-Chávez, J., Ponce-Mejía, D., Fontecha, G., & Ortiz, B. (2023). Tinea unguium caused by Epidermophyton floccosum. Bionatura, 8(3), 1–10. https://doi.org/10.21931/rb/2023.08.03.36 THANK YOU!