Micologia, Virologia e Microbiologia Clínica 01/03

Summary

In this lesson on mycology, the focus is on cutaneous mycoses, which affect keratinized structures like skin, hair, and nails. The discussion covers various types of dermatophytoses, caused by dermatophytes, and highlights the role of opportunistic fungi such as Candida and Fusarium. Key fungal species responsible for these infections, their transmission, and their impact on aesthetics are explained. The importance of proper treatment and the risks of home remedies are also addressed. Special attention is given to preventing the spread of these infections through shared items like shoes and manicure tools.

Takeaways

• 😀 Dermatophytoses (cutaneous fungal infections) are caused by dermatophytes, fungi that break down keratin in hair, nails, and skin.
• 😀 These infections typically do not cause significant immune response, leading to less severe symptoms, primarily affecting aesthetics.
• 😀 Common sources of dermatophytes include anthropophilic (human-adapted), zoophilic (animal-adapted), and geophilic (environmental) fungi.
• 😀 Cutaneous fungal infections are contagious and can spread through contact with infected areas or shared items like footwear and nail tools.
• 😀 The most common dermatophytes causing skin infections include Trichophyton, Microsporum, and Epidermophyton.
• 😀 Symptoms of dermatophytes infections may include discolored, thickened, or brittle nails, especially in fungal nail infections.
• 😀 Dermatophytes infections of the scalp (tinea capitis) can cause hair loss and are caused by fungi like Microsporum and Trichophyton.
• 😀 Fungal infections of the skin can present with lesions that may appear as red or dark-bordered patches, often seen in athlete's foot.
• 😀 Laboratory diagnosis of fungal infections involves direct microscopic examination to identify fungal filaments and cultures to confirm the species.
• 😀 Treatment for fungal infections typically includes topical antifungals, and in more severe cases, oral medications. Home remedies (e.g., bleach) should be avoided due to potential resistance and recurrence.

Q & A

What are cutaneous mycoses, and how do they differ from superficial mycoses?

Cutaneous mycoses are fungal infections that affect deeper layers of the skin, specifically structures containing keratin, such as hair, nails, and skin. Unlike superficial mycoses, which only affect the surface of the body, cutaneous mycoses have a closer relationship with the affected organ, but they do not cause significant immune system sensitization or severe symptoms.

What are the primary causes of cutaneous mycoses?

The primary cause of cutaneous mycoses are dermatophytes, which are fungi that break down keratin in the skin, hair, and nails. While most dermatophytes are the primary causative agents, opportunistic fungi like Candida and Fusarium can also cause cutaneous mycoses.

How do dermatophytes cause cutaneous infections, and what are the main types?

Dermatophytes cause infections by parasitizing keratinized structures, such as hair, skin, and nails. The main types of dermatophytes are anthropophilic (adapted to humans), zoophilic (transmitted from animals), and geophilic (from the soil). Each type has different characteristics, such as how they spread and the areas they affect.

What is the difference between 'endothrix' and 'ectothrix' dermatophyte infections?

'Endothrix' infections are those where the fungus grows inside the hair shaft, while 'ectothrix' infections occur outside the hair. For example, Microsporum causes 'endothrix' infections, while Trichophyton causes 'ectothrix' infections.

Why are cutaneous mycoses often not severe, and what symptoms do they cause?

Cutaneous mycoses typically do not result in severe symptoms because the immune system does not significantly react to them. The primary symptoms are aesthetic in nature, including changes in appearance like thickened, discolored nails, or scaly patches on the skin.

How do dermatophytes affect the scalp, and what are the specific types of scalp infections?

Dermatophytes affecting the scalp cause 'tinea capitis' or dermatophyte infections that can lead to hair loss. These infections can be caused by fungi from the Microsporum or Trichophyton genera. The types of infections include 'endothrix' infections (Microsporum) and 'ectothrix' infections (Trichophyton).

What is 'athlete's foot,' and how can it be prevented?

'Athlete's foot' is a common fungal infection caused by dermatophytes affecting the feet, often between the toes. It can present as vesicles and itching. Prevention includes avoiding direct contact with contaminated surfaces, not sharing shoes, and practicing good hygiene.

What are the risks of sharing personal items, such as footwear or nail care tools, in relation to fungal infections?

Sharing personal items, like shoes or nail care tools, can facilitate the transmission of dermatophytes and lead to fungal infections like athlete's foot or nail infections. It's essential to avoid sharing these items, especially if someone has visible fungal lesions.

Why should people avoid using home remedies like bleach or disinfectants to treat fungal infections?

Home remedies like bleach or disinfectants can harm the fungus but may not completely eliminate it. These treatments can cause the fungus to hide temporarily, and once the treatment stops, the infection may return, sometimes even with increased resistance.

What are the laboratory methods used to diagnose dermatophyte infections, and what do they reveal?

Diagnosis of dermatophyte infections involves direct microscopy, where fungal filaments are observed, and culturing the sample in selective media. The cultures can reveal fungal growth, often seen as cotton-like colonies with a yellow or brown pigmentation, helping identify the specific species of fungus.