A laboratory is differentiating dermatophyte species using in vitro hair perforation test. Which dermatophyte demonstrates positive hair perforation, forming wedge-shaped perforations in hair shafts after incubation?
- A Trichophyton rubrum
- B Trichophyton mentagrophytes ✓
- C Epidermophyton floccosum
- D Microsporum canis
Correct answer: B. Trichophyton mentagrophytes
Explanation
Trichophyton mentagrophytes produces perforating organs that wedge into hair shafts in vitro, giving a positive hair perforation test. Trichophyton rubrum is characteristically negative. This test helps differentiate these two common dermatophytes causing tinea. Epidermophyton and Microsporum species do not invade hair and are negative.
Reference: Jawetz, Melnick, & Adelberg's Medical Microbiology, 28th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.