Which dermatophyte genus is most commonly implicated in tinea pedis and onychomycosis?

Which dermatophyte genus is most commonly implicated in tinea pedis and onychomycosis?

• A. Microsporum canis
• B. Epidermophyton floccosum
• C. Candida albicans
• D. Trichophyton (especially Trichophyton rubrum)

Answer: (D)

The most common dermatophyte causing both tinea pedis (athlete’s foot) and onychomycosis (nail infection) is Trichophyton rubrum. This species is especially well adapted to the human keratinized tissues of skin and nails, producing keratinases that effectively degrade keratin and allow invasion of the nail plate and interdigital skin. Its preference for human hosts and its ability to persist in the nail and skin with relatively mild inflammation explain why it dominates these infections and often leads to chronic, recalcitrant courses. Other options fit different patterns: Microsporum canis is more frequently associated with animal contact and tends to cause tinea corporis or tinea capitis rather than nails; Epidermophyton floccosum can cause tinea pedis and onychomycosis but is less commonly the culprit compared with T. rubrum; Candida albicans is a yeast, not a dermatophyte, and it typically causes candidal infections rather than dermatophyte nail or foot infections.

The most common dermatophyte causing both tinea pedis (athlete’s foot) and onychomycosis (nail infection) is Trichophyton rubrum. This species is especially well adapted to the human keratinized tissues of skin and nails, producing keratinases that effectively degrade keratin and allow invasion of the nail plate and interdigital skin. Its preference for human hosts and its ability to persist in the nail and skin with relatively mild inflammation explain why it dominates these infections and often leads to chronic, recalcitrant courses.

Other options fit different patterns: Microsporum canis is more frequently associated with animal contact and tends to cause tinea corporis or tinea capitis rather than nails; Epidermophyton floccosum can cause tinea pedis and onychomycosis but is less commonly the culprit compared with T. rubrum; Candida albicans is a yeast, not a dermatophyte, and it typically causes candidal infections rather than dermatophyte nail or foot infections.