7 topics with concise reviews: definitions, key facts, and class questions.
In this section, we analyze the causative agents of superficial mycoses—keratinophilic fungi that affect the epidermis, hair, and nails. You will study the general characteristics, ecology, and morphology of dermatophytes, as well as the specifics of their epidemiology.
Special attention is paid to specific microbiology: pathogenesis, clinical manifestations, and algorithms for the laboratory diagnostics of dermatomycoses. We will examine in detail the classic triad (microsporia, trichophytosis, favus), and also touch upon nodular trichosporioses—black and white piedra.
During practical classes and exams, instructors most frequently ask about the rules for collecting pathological material (skin scales, affected hair), the growth characteristics of fungi on Sabouraud agar, and the differential microscopic picture (for example, the arrangement of endo- and ectothrix spores). This knowledge is an essential foundation not only for passing microbiology, but also for future work in dermatovenereology and general practice.
What is the difference between the morphology of Piedraia hortae in vivo and in vitro?
On the hair (in vivo), the fungus reproduces sexually, forming asci (spore sacs). On nutrient media (in vitro), asexual reproduction occurs with the formation of mycelium and chlamydospores.
What microscopic feature is primary for differentiating dermatophyte genera?
The main feature when studying pure culture is the morphology of macroconidia—large asexual spores (their shape, wall thickness, presence of spines).
Why is it necessary for a physician to know the ecological classification of dermatophytes when a mycosis is suspected?
This is a key point for taking an accurate epidemiological history. Understanding whether a fungus belongs to anthropophiles, zoophiles, or geophiles allows for precisely determining the source of infection — an infected person, an animal, or contact with soil.
Why do dermatophyte fungi infect only the upper layers of the skin?
These fungi are keratinophiles—they feed on keratin. Since keratin is present only in the epidermis and its appendages, they cannot penetrate deeper than the basement membrane.
What does the hair lesion type "ecto-endothrix" mean?
This is a type of invasion where fungal elements spread both inside the hair shaft (endo-) and on its surface (ecto-), forming a mosaic spore sheath around the hair.
What is "mat pox" ("ringworm of gladiators")?
This is a specific form of superficial trichophytosis found in wrestlers. The causative agent is T. tonsurans, and transmission occurs through close physical contact.
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