| Malassezia species are members of the human cutaneous commensal flora, at the some time a kind of opportunistic pathogen. It can cause cutaneous diseases and systemic infection in special envitronment and suitably predisposed individuals. Malassezia can be the agents of pityriasis versicolor, malassezia follicolitis, onychomycosis, fungemia, and related to atopic dermatitis, seborrhoeic dermatitis, dandruff and psoriasis. At present, the pathogenisis is not well elucidated. Studies of malassezia local infection are mostly focus on pityriasis versicolor and malassezia follicolitis. Pityriasis versicolor is a mild, chronic condition, usually affecting the upper trunk. The condition occurs mainly between adolescence and middle age, when the sebaceous glands are more active. Predisposing factors include a genetic susceptibility, illness or malnutrition, increased plasma cortisol level , and high ambient temperature and humidity . The incidence is higher in tropical climates, and the lesions may be more extensive in tropical climates. In temperate regions, microscopically the appearance is classically of clusters of yeasts with hyphae that may be branched, being described as spaghetti and meatballs. While in tropical regions, oval or cylindrical yeasts with filaments may be seen. Malassezia furfur, Malassezia sympodialis and Malassezia globosa were reported to cause pityriasisversicolor. Malassezia follicolitis is a chronic, easy recrudescent desease, usually affecting chest, back, neck and face. Predisposing factors include inner and outer factors. The inner factors include greasy skin, using antibiotic or cortisol or immunosuppressant, apparatus transplantation, immune system in low function, malignancy, pregnancy and diabetes. The outer factors include high ambient temperature and humidity. Malassezia globosa and Malassezia furfur were reported to cause malassezia follicolitis. Compared to pityriasis versicolor and malassezia follicolitis, we can find they have similar predisposing factors and pathogen, but clinical characters are dissimilarity. Their nosogenesis must are different. We made guinea pig animal model of local infection with M. furfur, M. sympodialis and M. sloofiae, researched deeply through histopathologic method and transmission electronic microscopy, and using statistical methods analyse the results. The aim of this study is to clarify the pathogenesis^ histopathological changes and ultrastructure changes of different malassezia and different number infecting local skin. To provide basic information for the research of Malassezia associated skin diseases's pathogenesis.Materials and methods:1. Forty-five male guinea pigs were divided into 3 groups randomly, 15 guinea pigs in each group. Applied depilating agent to depilate guinea pig back, and formed 4 areas with depilation. Injected malassezia suspensions 0.2ml in epidermis on both sides of the top areas with depilation. A,B and C group respectively injected M.fur, M. sym and M. slo suspensions. The malassezia suspensions concentration injected in left side was lxl08spores/ml, right side was 8xl06spores/ml. Subjacent depilated areas were injected 0.9%NaCl 0.2ml as negative antitheses.2. 10% hydration chloroacetal was injected in abdominal cavity on lst,3rd,7th,14th and 21th day after injection, and made injected skin into samples. Hematoxylin and eosin stain, periodic acid-Schiff stain and transmission electronic microscopy were used to examine the pathogenetic fungus, histopathological and ultrastructural changes in focus.3. Statistical tool: SPSS 10.0 software system. Using two-sample Mest for independent samples, two-way ANOVA, Fisher's exact test of probabilities and tendence x test analyze the data.Results:1. Local focuses appeared red inflammatory papulaes. The diameter of both sides papulaes of each group had significant difference on 1st and 3rd day(p<0.0l). The papulaes diameter of left focuses among three groups had significant difference on 3rd(p<0.05).2. Malassezia in focuses were took up and eliminated by phagocyte The ratio of focus malassezia were eliminated had significant difference in both sides focuses of B group on 1st week (p<0.05). The ratio of focus malassezia eliminated had significant difference in both sides focuses of each group on 2nd week (p<0.01).3. Inflammatory cells infiltration, degeneration and necrosis, abscess, granuloma could be observed in focuses. With the time went on, the focuses got right structure gradually. There was a significant difference on the ratio of focus getting right in both sides focuses of each group on 2nd week (p<0.0l).4. All the focuses epidermis appeared hyperplasia phenomenon in different degree, especially from 1st week to 2nd week. At the same time, epidermis basal cells proliferation towards focus were observed in part of the focuses, and formed cyst around focus. This phenomenon commonly occurred between 3rd day and 1st week. There were no significant difference in this phenomenon positive percent of A and B groups both sides focuses on 1st week and 2nd week (p>0.05). The positive percent between left and right focuses in C group had significant differences on 1st week and 2nd week(p<0.05). There was a significant difference on the general masculine ratio of left focuses among three groups (p<0.05).5. Ultrastructural changes of malassezia cell include cell distortion, cell wall perforation, the inner structure of cell disappearance.Conclusion:1. The inflammatory reaction degrees in guinea pig local skin's focus are related with the malassezia quantities in focuses. The more quantities, the more severity the inflammatory reaction is. The inflammatory reaction degrees are also related with the malassezia species.2. The malassezia in guinea pig cutaneous focuses are taken up and eliminated by neutrophils in forepart,later mainly by macrophages. The more quantities of malassezia are, the much longer time needs to eliminate malassezia.3. The malassezia focuses in guinea pig local skin can appear granuloma. The focuses getting right are related with the malassezia quantities. The more quantities of malassezia are, the much longer time needs for focus to get right.4. The malassezia focuses can induce local epidermis basal cells to proliferate and form cyst around focus. This phenomenon is related with malassezia species and malassezia quantities. M.slo focuses occur this phenomenon much more than M. fur and M. sym focuses. The more quantities of M. slo in focus, the higher positive percent is. |
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