A Study Of Biological Characteristics And Genetic Analysis Of Microsporum Canis

Background:Microsporum canis is a kind of dermatophytosis which belongs to Deuteromycotina-HyPhomycetes-Moniliales-Moniliaceae-Microsporum which trends to invade skin and fur of animals.It is found on the skin of some animals like cats, dogs and rabbits and can transfer from animal to animal as well as from animal to people.Previous studies show that M.canis can result in diseases such as tinea capitis, corpus capitis and few onychomycosis,especially tinea capitis.It has always being known as one of the most important superficial mycosis all over the world.With a popular phenomena of keeping pets,the rate of tinea capitis rises sharply during those years.M.canis is the main pathogen of tinea alba and kerion,which plays a crucial role in the prevalence of tinea capitis.Besides,M.canis can cause outbreak of tinea capitis to certain people in some situations.In conclusion,it is significant to farther research for this pathogenic fungus.Objective:1.To investigate the etiology,clinical features of M.canis in Lanzhou district.2.To inquire into the application of rapid and precise identification for the superficial mycosis by using molecular methods.3.Observe the broth microdilution antifungal susceptibility about M.canis of Lanzhou district and prove the reproducibility and feasibility of M38-A procedure which can be used for the antifungal susceptibility test to dermaphytes in the laboratories,especially M.canis.Method:The specimens are from suspected patients who suffered from tinea capitis and corpus capitis and came to No.2 Attached Hospital of Lanzhou University during 2007.6-2007.12.The patients were examined microscopically with positive results are questioned about history and related clinical information is detailed.The specimens of these cases were cultured on Sabouraud - chlorlamphenicol glucose agar (SDA)and Rice grain medium(RGM),the species being identified with growth rate of isolates,production and direct microscopic examination.After that,we approached the broth microdilution antifungal susceptibility testing condition which was recommended by CLSI in 2003 tested the minimal inhibitory concentration(MIC)of 5 antifungal drugs to 55 M.canis.We also extracted the DNA of the 55 M.canis by mini-preparation.The internal transcribed spacer(ITS)region of ribosomal DNA were amplified by the fungi-universal primers ITS1(5'-TCCGTAGGTGAACCTGCGG -3')and ITS4(5'-TCCTCCGCTTATTGATATGC-3').Following restriction fragment length polymorphisms(RFLP)was performed by two restriction enzymes(HinfⅠ, TaqⅠ)digesting those production of polymerase chain reaction(PCR)amplification.Results:1.Among 55 cases,47 patients suffered from tinea capitis(85.45%)and 8 patients suffered from corpus captitis(14.55%).The ages were from 1-47.Patients under 10-year-old were 52 cases which occupied 94.54%in the whole specimens. Male were 40(72.72%)and female were 15(27.27%).Patients living in Lanzhou city are 42(76.36%)and these living in town and countryside were 13(23.63%).The 49 patients(84.09%)admitted to contact animals especially pets during 2 weeks and 1.5 years,while 8 patients once played with children with tinea capitis.We also found 2 cases of more children in the same families got the tinea capitis one by one.2.The patterns of 55 strains of M.canis were isologous after the primer-pair ITS1 and ITS4 being amplified,and about 760 bps were obtained in M.canis.3.The patterns of two restriction enzymes HinfⅠand TaqⅠwere respectively identical with two bands.4. The range of the drugs are:Itraconazole,0.25-1ug/ml,Econazole,0.25-2μg/ml, Terbinafine,0.01-0.04μg/ml,Griseofulvine,0.25-1μg/ml.Fluconazole,1-32μg/ml respectively.Conelusion:1.Majority of patients' are less than 10-year-old.The main clinical type of tinea capitis is tinea alba.2.PCR of ribosomal DNA intergenic spacer regions is a useful method for species identification of common dermatophyte fungi.3. Restriction enzymes HinfⅠand TaqⅠdigestion of PCR amplified ITS regions produce unique and easily identifiable fragment patterns for M.canis species.4.M. canis are sensitive to the five drugs.There are significant differences of MIC among these 5 drugs,which provide a reference to us to use these drugs properly.