Dermatophytes are

Ans: (b) Trichophyton rubrumRef: Harrison 17th ed. /1309DERMATOPHYTOSIS OR RING WORM (TINEA) INFECTION* Dermatophytes include a group of fungi (ring worm) that under most conditions have the ability to infect & survive only on dead keratin; that is the superficial topmost layer of skin (stratum corneum or keratin layer), hair and nails.* They cannot survive on mucosal surfaces (eg mouth or vagina) where the keratin layer does not form.* The ring worm fungi belongs to 3 genera:TrichophytonMicrosporumEpidermophyton* Infects skin, hair & nail* Infecting species include:# Trichophyton rubrum# Mentagrophyte# Violaceum# Verrucosum# Schoenleinii* Infects skin and hair but does not involve nails* Several infecting species include: Microsporum audounii, M. gypseum and M. canisInfect skin & nails but does not involve hair Only infecting species is Epidermophyton floccosum.Mnemonic* TSH-N (Trichophyton infects Skin, Hair and Nail)* MSH (Microsporum infects Skin and Hair)* ESN (Epidermophyton infects Skin and Nail)