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INTRODUCTION

The least invasive of the pathogenic fungi are the dermatophytes and other superficial fungi that are adapted to the keratinized outer layers of the skin. Subcutaneous fungi go a step farther by extending infection to the tissue beneath the skin but rarely invading deeper structures (Table 45–1).

TABLE 45–1Agents of Superficial and Subcutaneous Mycoses

SUPERFICIAL FUNGI

DERMATOPHYTES

Overview

Dermatophytoses are superficial infections of the skin and its appendages. Common names for these infections include ringworm (Figure 45–1), athlete’s foot, and jock itch. They are caused by species of three genera collectively known as dermatophytes. These fungi are highly adapted to the nonliving, keratinized tissues of nails, hair, and the stratum corneum of the skin. The source of infection may be humans, animals, or the soil.

FIGURE 45–1.

Ringworm. The ring-like lesions on this forearm are due to advancing growth of Trichophyton mentagrophytes. (Reproduced with permission from Willey JM: Prescott, Harley, & Klein’s Microbiology, 7th ed. New York, NY: McGraw Hill; 2008.)

MYCOLOGY

The three genera of medically important dermatophytes (literally, skin-plants) are Epidermophyton, Microsporum, and Trichophyton (Table 45–1). Most dermatophyte infections are diagnosed and treated as a clinical syndrome since determining the causative species will not usually affect therapeutic choices. These fungi require a few days to a few weeks to grow in culture, and they are typically isolated ...

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