医学真菌学 （ medical mycology ）

Comparison of fungi and bacteria FeatureFungiBacteria diameter 4 µ m 1 µ m nucleuseukaryoticprokaryotic cytoplasmwith mitochondria and endoplasmic reticulum without mitochondria and endoplasmic reticulum Cell membranesterol presentsterol absent Cell wallchitinpeptidoglycan sporessexual and asexual spore for proliferation spore for survival, not for proliferation dimorphismyesNo metabolismRequire organic carbon and no anaerobes May do not require organic carbon and maybe anaerobes

Role of fungi in nature There are approximately 70,000 recognized species of fungi. Most are beneficial to humankind. –production of food –antibiotics and immunosuppressive drugs –used as model systems in molecular biology

Medical Mycology the subject on pathogenic fungi –Some fungi act as the plant and animal pathogens in the agricultural industry. –About 300 species of fungi cause human infections.

Cellular Morphology A pathogenic fungi can exist either as yeasts （酵母菌） or as mold ( 霉菌 ).

Yeasts Yeasts are unicellular organisms without hyphae.

Yeast propagation The yeasts propagate usually by budding and rarely by binary fission. If the yeast continue to propagate by forming more and more buds, but do not detach from one another, they will produce elongated forms similar to hyphae called pseudohyphae.

A. Yeast cells propagating by budding B. Yeast dividing by binary fission C. Development of pseudohyphae 增殖方式

Molds Molds have two different structural parts: Hyphae and Spores. Hyphae are multi-cellular filamentous structures. Hyphae form branches and the pattern of branching is helpful for morphological identification.

hyphae/molds

Thus, a mold is multicellular microbes composed of two parts: spore and hypha. Hypha spore

according to hyphae do or do not have septa they are called septate or nonseptate hyphae.

Asexual spores An aerial hyphae often produces asexual propagules named asexual spores (produced by one cell). Conidium is the most common asexual spore. Relatively large and complex conidia are termed macroconidia, while the smaller and simpler conidia are termed microconidia. When many conidia are enclosed in a sac, it is called as endospores / sporangiospore.

Asexual spores Sporangiospore( 孢子囊孢子 ):many conidia are enclosed in a sac

Asexual spores Conidium （分生孢子） –macroconidia, large and complex conidia –microconidia the smaller and simpler conidia

macroconidia

microconidia

Asexual spores Thallospore ( 叶状孢子 ) –Arthrospore ( 关节 ) –Chlamydospore ( 厚膜 ) –Blastospore ( 芽生 )

Arthrospore ( 关节 )

Chlamydospore ( 厚膜 )

Blastospore ( 芽生 )

Sexual spores Sexual spores are produced by fusion of one male and one female cell. They include ascospore （子囊孢子）, basidiospore （担孢子）, oospore （卵孢子） and zygospore （接合孢子）。

The size, shape and location of spores are used in laboratory to identify some species of fungi.

Dimorphic fungi Some fungi exist in both yeast and mycelial forms. These fungi are called dimorphic fungi. Yeast form: a parasitic or pathogenic form. This form is usually seen in tissue of patients. Can be cultured at 37 ℃. Conversion to yeast form appears to be essential for pathogenicity. Mycelial form: a saprophytic form. This is the form existing in nature. Can be cultured at 25 ℃.

Yeast type colony Filamentous type colony

Culture & Colony morphology Sabouraud culture medium. Optimal pH 4-6. Optimal temperature ℃, 37 ℃ for certain pathogenic fungi. Aerobic.

Types of colonies 1. Yeast type colony are usually soft, opaque, 1-3 mm in size and cream colored. 2. Yeast-like type colony is similar to yeast type colony but forms pseudohyphae. 3. Filamentous type colony have special features such as various hyphae and special pigmentation.

Unicellular fungi (one cell means one fungus, e.g., yeast fungus) form yeast or yeast-like colony. Multicellular fungi (many cells consist one fungus, e.g., mold) form filamentous type colony.

Unicellular fungi

Multicellular fungi

Fungi have strong resistance to dryness, sunlight, UV light and many chemical agents, but much sensitive to wet heat. Resistance

The antibiotics to treat fungal infectious diseases are quite different compared to those to cure bacterial infectious diseases: amphotericin B ( 两性霉素 B), anticandine ( 制霉菌 素 ), miconazole ( 咪康唑 ), ketoconazole ( 酮康唑 ) etc. The most effective antifungal drugs exploit the presence of ergosterol （麦角固醇） in fungal cell membranes that is not found in bacterial or human cell membranes. Drugs

Fungal diseases in human tend to be relatively benign and few of fungal diseases are life-threatening. Fungal diseases are an increasing problem due to the use of antibacterial and immunosuppressive agents. Individuals with an altered bacterial flora or compromised defense mechanism easily have more opportunistic fungal infections than healthy people. Fungal diseases

Major clinical manifestations of fungal diseases: ◇ Hypersensitivity ： an allergic reaction to molds and spores. ◇ Mycotoxicosis: poisoning of human and animals by food contaminated with mycotoxins. ◇ Infectious diseases: caused by exogenous pathogenic fungi or endogenous fungi (opportunistic infections). ◇ Inducing tumors: Some mycotoxins can induce tumors (e.g., aflatoxin causes liver cancer) ( 黄曲霉素 ).

A.Superficial mycoses: Infections are limited to the hair or the outermost layers of skin.

common superficial mycoses （花斑癣） :

B. Cutaneous mycoses: Fungi invade the keratinized layers ( 角化层 ) of skin, hair and nails and the diseases are limited in these layers. The fungi causing these diseases are termed dermatophytes ( 皮肤癣真菌 ). The diseases are referred to as tinea ( 癣病 ).

All tinea are caused by members of three genera: Trichophyton ( 毛癣菌 ) Epidermophyton ( 表皮癣菌 ) Microsprum ( 小孢子癣菌 ) Unlike the superficial mycoses, cellular immune responses may be evoked

common cutaneous mycoses:

C. Subcutaneous mycoses: The infections involve the dermis, subcutaneous tissue, muscle and fascia.

common subcutaneous mycoses:

D. Systemic mycoses: the infections originate primarily from the lung and then spread to many other organs

◇ Fungi causing systemic mycoses: Cryptococcus neoformans ( 新型隐球菌 ) Histoplasma capsulatum ( 荚膜组织胞浆菌 ) Blastomyes dermatitides ( 皮炎芽生菌 ) Paracoccidiodes brasiliensis ( 巴西副孢子菌 )

Cryptococcus neoformans ( 新型隐球菌 ) Oval, budding yeast surrounded by characteristic thick polysaccharide capsule.

C. neoformans with capsule is negatively stained by India Ink

Disease Cryptococcosis （隐球菌病） –Acute or chronic infections in the lung, bone and skin, and meningitis –meningitis can last several months and are highly fatal No human to human transmission –Infection follows inhalation of pigeon or chicken droppings containing the microbe

Opportunistic mycoses Patients or individuals with immune deficiency are easily suffering from opportunistic mycoses caused by fungi belonging to normal flora.

The major pathogens causing opportunistic mycoses are as the following: Candida ( 假丝酵母菌 ) Aspergillus ( 曲霉菌 ) Mucor ( 毛霉菌 ) Opportunistic mycoses

8 species in the genus Candida can infect humans and cause disease called candidiasis. Among the 8 pathogenic species, Candida albicans ( 白假丝酵母菌 ) is the most common species to cause diseases in skin, mucosa, internal organs and central nervous system.

Candida albicans can be found in 40-80% of normal human beings. It is present in mouth, intestine and vagina.

Candida albicans is dimorphic fungus. Candida albicans can show germ tubes with special shape, which used as a diagnostic feature of the microbe.

Pseudohyphae and hyphae of Candida albicans using Methenamine Silver Stain.

Oral thrush （鹅口疮） is a typical and common disease caused by Candida albicans

Gram-staining of vaginal smear showing Candida albicans on the epithelial cells.

第一层是自然地境界。

第二层是自发的境界。

第三层是自由的境界。

防治考试作弊的境界