Experimental Dermatophytosis Of A Guinea Pig Model Using Trichophyton Rubrum

1.To isolate and identificate a Trichophyton raubitschekii strain from a male adult tinea cruris patient.Methods Fungal infection was proven by direct microscopic examination.Dermatophytosis was diagnosed by culture.Urase tests,PCR of ribosome DNA ITS region and sequencing methods were adopted to identify the dermatophyte strain.Results The isolate was identified as T.raubitschekii by the following phenotypic features:(1)velvety colony on SDA plate,reddish staining could be seen on PDA plate after 2 weeks;(2)rod-shaped microconidia, pencil-shaped macroconidia and abundant arthroconidia;(3)positive urease activity could be seen in a week,negative hair perforation test after 2 weeks; Molecular diagnosis were performed by sequencing analysis of rDNA ITS region and blast with the reported rDNA ITS region sequence of Trichophyton rubrum. The ITS sequence of T.raubitschekii,was found to be identical with that of T. rubrum.Conclusion This strain was identified as T.raubitschekii,which was the first isolation in China.2.To construct an animal model infected by Trichophyton rubrum.Methods Three different strains of Trichophyton rubrum were separated from clinical specimen for the infection of 16 guinea pigs as three different groups.Corticosteroids were given before and after the construction of animal model to facilitate the infection. Direct microscopic examination,culture and histopathology methods were adopted to verify the construction.Results Ten days after the inoculation of Trichophyton rubrum,with the intervention of corticosteroid,the guinea pigs were examined.Prominent scales and inflammation could be seen on the inoculation site of all the Trichophyton rubrum infected guinea pig.Scales and hairs of Trichophyton rubrum infected guinea pig dealed with 10%potassium hydroxide, hypha out of the hair and microconidia or hypha in the hair shaft could be seen.7 days after the inoculation of scales and hair on SDA plate,cultures of Trichophyton rubrum showed that the colonial morphology were identical to the dermatophytes innoculates.PAS staining of infected guinea pig skin tissue showed that hypha and microconidia could be seen in the infundibula and hair root.Conclusion With the intervention of corticosteroid,a stable guinea pig model infected by Trichophyton rubrum can be constructed,which may have a potential pharmacal use in the future.3.To investigate the ability to degradate animal hair of Trichophyton rubrum. Methods A liquid medium,which contains 0.05%yeast extract in water solution, was adopted.T.raubitschekii,T.rubrum or T.mentagrophytes were inoculated into the liquid separately,and child hair,guinea pig hair or mouse hair were added into the culture respectively.Dermatophyte colony foundation was observed everyday.2 weeks later,the growth of the dermatophyte colony and changes of the hair under light microscope were observed.Results After 2 weeks,T. raubitschekii,T.rubrum and T.mentagrophytes could grew on the medium which contains guinea pig hair or mouse hair.Normal structure of the hair changed due to the growth of dermatophytes.Transverse striation of both hairs blurred or disappeared.Conclusion As T.mentagrophytes do,T.rubrum can also degradate animal hair keratin to sustain its development.