Which species is the 2nd most common and causes T. pedis, T. corporis, T. cruris, and onychomycosis?

• A. Trichophyton tonsurans
• B. Microsporum gypseum
• C. Trichophyton rubrum
• D. Candida albicans

Answer: (C)

Trichophyton rubrum is the most common dermatophyte responsible for infections of keratinized tissues, including the skin and nails. It thrives on human skin and nails, is easily transmitted person-to-person, and tends to cause chronic infections. This combination makes it the leading cause of tinea pedis (athlete’s foot), tinea corporis (ringworm of the body), tinea cruris (jock itch), and onychomycosis. Among the organisms listed, rubrum best fits the pattern of causing all four conditions, which is why it’s the best answer.

Trichophyton tonsurans is more typical for scalp infections like tinea capitis; Microsporum gypseum is less common and often linked to zoophilic/geophilic exposures; Candida albicans is a yeast that can cause nail infections in certain contexts but is not the usual cause of these dermatophytoses.