Hair perforation test is positive in infection with ?
Trichophyton
Microsporum
Epidermophyton
All of the above
Ans. is 'a' i.e., Trichophyton Hair perforation test . The hair perforation test consists of inoculating colonies of an organism into a dish containing a small amount of water, a few drops of yeast extract solution and some human hair. The dish is incubated at 300C and after 7 days, some of the hair are taken and are kept on a slide with a coverslip and are observed under a microscope. The test is considered positive if the hair has deep, narrow wedge shaped perforation in it. . Hair perforation test is done to distinguish between isolates of dermatophytes, paicularly trichophyton mentagrophytes and its variants.