| Objective: Dermatophytes have been classified into three genera, Trichophyton, Microsporum and Epidermophyton. They invade keratinized tissues of human and other animal, that is, superficial cornified skin layers, hair and nails, causing a superficial cutaneous infection called dermatophytosis. Dermatophytes which produced an infection to laboratory animal are mainly Trichophyton mentagrophytes, Microsporum gypseum and Microsporum canis. The three kinds of dermato- phytes should be banned to laborary animal, no matter they were isolated in infectious sites or uninfectious sites. Because the dermatophytes in uninfectious sites was probable causing dermaophytosis of laboratory animal and producing infection to laboratory man.The current diagnosis of dermatophytosis is based upon the status of colony and microscopic identification of hyphae directly from lesion materials followed by in-vitro culture. Although rapid and economical, microscopical examination is not species-specific and needing a lots of experience. In fact, the phenotypic characteristics of dermatophytes can be easily influenced by outside factors, such as temperature variations, chemotherapy and culture media, that may interfere with the metabolic process of the dermatophyte and affect the interpretation of in-vitro culture results. In-vitro culture is capable of providing typical characteristics of morphological and biochemistry in 10~15 days. However, for some unusual and atypical characteristic dermatophytes, identification may require a range of special culture media. These tests will consum several weeks. PCR technology which is high sensitivity, speciality and rapidity have been used for dermatophytes identification. Now these studies amplified DNA of dermato- phytes selecting universal primers which get from 18S, 25S ,28S ribosomal RNA genes and internal transcribed spacer (ITS) regions, as well as chitin synthase 1 gene, and these methods frequently require additional manipulation such as sequencing after amplification or restriction endonuclease digestion. Except that, random amplification and identification of DNA fragments unique to a certain strain or species in RAPD enables various dermatophytes to be differentiated rapidly and precisely from each other. But there are hundreds of various fungi related to medicine, and several decades of dermatophytes. Now there is no one molecular biology method which enable to identificate species of dermatophytes with rapidity, simplicity and accuracy.Dermatophytes have strong cell walls which are often resistant to traditional DNA extraction procedures. Now there are already some reports about extraction methods of dermato- phytes DNA, such as enzyme method (Novobiocin), glass beads method, ground with a pestle et al. These methods are either costing, or affecting the quality of DNA. And traditional DNA extraction procedures are steps-repeating and time-consuming, and making people feel tired.The test develop a method of nucleic acid identification with high sensitivity, speciality and rapidity to detect pathogenic dermatophytes in laboratory animals. And to establish a rapid and simple DNA isolation method from pathogenic dermato- phytes in laboratory animal by comparing several methods of extraction dermatophytes DNA.Methods: The standard strains (Trichophyton menta- grophytes, Microsporum gypseum and Microsporum canis) were inoculated on to Sabouraud dextrose agar and cultured at 27℃ for 7 days. Then Trichophyton mentagrophytes and Microsporum gypseum were cultured in Sabouraud liquid medium and incubated with shaking for 10 days at 27℃. The mycelial samples were collected by centrifugation and then put into 1.5ml Eppendorf tube in liquid nitrogen. The samples (about 10mg) were lysed with lysing enzyme, or grounded finely with a pestle in a prechilled mortar, or disrupted using a sterile toothpick. Then phenol-chloroform extraction method and potassium acetate extraction method were used to isolate DNA; A small lump of mycelia of Microsporum canis was scrapted from Sabourau...
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