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Ch. 17 - Skin and Eye Infections
Norman-McKay- Microbiology: Basic and Clinical Principles 2nd Edition
Norman-McKay2nd EditionMicrobiology: Basic and Clinical PrinciplesISBN: 9780137661619Not the one you use?Change textbook
Chapter 17, Problem 8

Select ALL the true statements about dermatophytes:
a. They are a group of bacteria that cause cutaneous infections.
b. They may be treated with antifungals without knowing the exact causative agent.
c. They are easily treated with antibiotics.
d. They are commonly acquired from the soil, environment, or animals.
e. They produce enzymes that digest keratin found in hair, nails, and skin.

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1
Step 1: Understand what dermatophytes are. Dermatophytes are a group of fungi, not bacteria, that cause cutaneous (skin) infections by invading keratinized tissues such as hair, nails, and skin.
Step 2: Evaluate statement (a). Since dermatophytes are fungi, not bacteria, statement (a) is false.
Step 3: Consider treatment options. Dermatophyte infections are typically treated with antifungal medications, and often treatment can begin empirically without identifying the exact species, making statement (b) true.
Step 4: Assess statement (c). Antibiotics target bacteria, not fungi, so antibiotics are ineffective against dermatophytes, making statement (c) false.
Step 5: Review statements (d) and (e). Dermatophytes are commonly acquired from environmental sources such as soil, animals, or contaminated surfaces, and they produce keratinase enzymes that digest keratin in hair, nails, and skin, so both (d) and (e) are true.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Dermatophytes as Fungal Pathogens

Dermatophytes are a group of fungi, not bacteria, that infect keratinized tissues such as skin, hair, and nails. They cause superficial infections known as dermatophytoses or ringworm, which are common cutaneous fungal infections.
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Introduction to Pathogenic Toxins

Keratinase Enzyme Production

Dermatophytes produce keratinase enzymes that break down keratin, a structural protein in skin, hair, and nails. This enzymatic activity allows them to invade and colonize these tissues, leading to characteristic infections.
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Treatment of Dermatophyte Infections

Dermatophyte infections are typically treated with antifungal medications rather than antibiotics, as antibiotics target bacteria. Empirical antifungal treatment is often effective even without identifying the exact fungal species.
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