Experimental Study Of Two Geotrichum’s Pathogenicity To Human Nails And Their Extracellular Enzymatic Activity

Objective: A model of fungal peretration to human nails was establishedto study if Geotrichum sivicola, Geotrichum candidum and Trichophytonrubrum could violate the health human nail in vitro.Then the damaged nailwould be observed by the scanning electron microscope(SEM). Next theextracellular enzymatic activity of three strains fungi was investigated. Finallyaccording to both of the result, we will analysis the correlativity between thepathogenicity and the extracellular enzymatic activity. G. Silvicola is a newstrain in Geotrichum, which we isolated from a child’s kerion-like lesions andthe blood of a patient suffered from toxic epidermal necrolysis respectively inour department. It firstly confirmed that G. silvicola can infect human. G.candidum is a typical strain of Geotrichum, which can cause systemicinfections but the bronchus to be infected at mostly. It wes never publishedcase reports about the onychomycosis by Geotrichum. T. rubrum is adermatophyte and mostly violate the human skin and nail. It is the mostlycommon pathogen to the onychomycosis in chinaMethods: Geotrichum candidum was identified by china Institute ofMicrobiology in Acdemt Science.we afforded it from here. GeotrichumSilvicola was identified by china Institute of Microbiology in Acdemt Science,it was conserved in a laboratory of Fungus Department of Dermatology.Trichophyton rubrum was bought from the First Hospital Beijing MedicalUniversity. All the strains of fungi were identified by cultivation,micromorphology,morphology and biochemical test.1. We established thesemodels and divided them into three groups of G.sivicola, G.candidum andT. rubrum. Then the passing time of3strains fungi was compared to study thepathogenicity.2. Microstructres of the damaged nails, the hyphae and sporewere observed by SEM.3.19extracellular enzymatic activity was investigated with the semiquantitative API-ZYM system (bioMerieux sa,France).Results:1. Three strains fungal can all peretrate the human nails in vitro,the passing time of G. sivicola, G. candidum and T. rubrum is (15.07±3.28)d,(14.50±1.67)d and (6.76±1.72)d. the passing time of G.sivicola andG.candidum was longer than T. rubrum respectively(P＜0.05). There was nostatistic difference between the passing time of G. sivicola and G. candidum (P＞0.05).2. It was showd that hyphaes of3fungi all could peretrate the horncell of nails by SEM. Compared with nail of negative control, the scale orderof the invaded kerationcytes in back nail surface was disappear. The edge ofcells was changed to fuzzy and the widths between cells was to vary.3.Alkaline phosphatase, chymotrypsin and the majority of sugar fermentingenzyme produced by T. rubrum were significantiy more than that ofG.sivicola and G.candidum. The extracellular enzymatic activity ofG.sivicola is like that of G.candidum. Those which were produced by all3strains fungi include esterase(C4), esterase lipase(C8), leucine arylamidase,valine arylamidase, acid phosphatase and Naphthol-ASBI-phosphohydrolase.Conclusion:1. G.sivicola and G.candidum can penetrate nail plate invitro,but their passing time is longer than T. rubrum respectively.2. SEMshowd that hyphaes of G.sivicola, G.candidum and T. rubrum all couldperetrate kerationcytes of nails.3. The extracellular enzymatic activity ofG.sivicola is like that of G.candidum.4. The majority of the extracellularenzymatic activity of T. rubrum were more than G. sivicola’s andG.candidum’s. Alkaline phosphatase, chymotrypsin and the majority of sugarfermenting enzyme is likely to act on breakdown or decomposition on thetissue of a nail.