Medical Mycology

1. Medical Mycology

2. Basic characteristics of fungi

3. Fungi are not plants or animals Unlike animals, most fungi are nonmotile and possess a rigid cell wall Unlike plants, fungi are nonphotosynthetic

4. Role of fungi in nature • There are approximately 80,000 recognized species of fungi. • Most are beneficial to humankind. • food • production of food • antibiotics and immunosuppressive drugs • used as model systems in molecular biology

5. 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.

6. Characteristics of fungi Each fungal cell has at least one nucleus with a nuclear membrane, endoplasmic reticulum, mitochondria and secretory apparatus Most fungi are aerobes Fungi secrete enzymes that degrade organic substrates into soluble nutrients which are then absorbed into the cell Fungi have rigid cell walls composed of glucans and chitins Maybe haploid or diploid Both sexual and asexual reproduction

7. Comparison of fungi and bacteria

13. Cellular Morphology • Yeasts: unicellular organisms • Molds: multicellular • Dimorphic fungi: capable of growth as a yeast or mold depending on environmental conditions

14. Yeast • Yeast are usually spherical to ellipsoid. • Most yeasts reproduce by budding. • Some produce buds that fail to detach and become elongated, producing a chain of elongated yeasts called pseudohyphae A blastospore is an asexual fungal spore produced by budding

15. Mold molds

16. amold is multicellular microbes composed of two parts:sporeandhypha. Hyphae spore

17. Hyphae Hyphae: Tubular, branching fiaments (2–10 μm in width) of fungal cells, the mold form of growth. Most hyphal cells are separated by porous cross-walls or septa. Mycelium: the mass of intertwined hyphae that accumulates during active growth. Vegetative hyphae anchor the colony and absorb nutrients. Aerial hyphae project above the colony and bear the reproductive structures.

18. Mycelium Mycelium: the mass of intertwined hyphae that accumulates during active growth.

19. Spore Spore: A specialized propagule with enhanced survival value, such as resistance to adverse conditions or structural features that promote dispersion. Spores may results from asexual (e.g. conidia. sporangiospores) or sexual reproduction. Most pathogenic fungi produce asexual spores.

20. Spores conidiophores macroconidia microconidia thallospores blastoconidia/ blastospores arthrospores chlamydospores sporangiospores

21. Conidium: asexual reproductive structures produced either from the transformation of a vegetative yeast or hyphal cell or from a specialized conidiogenous cell. Sporangiospore: Asexual mitotic spores produced within an enclosed sporangium. Sporangiospore conidium

22. macroconidia of Epidermophyton microconidia of Trichophyton sporangiospores of mucor 毛癣菌的小分生孢子 chlamydospores of Candida albicans macroconidia of Fusarium microconidia of Dematiaceae 镰刀菌的大分生孢子 着色真菌的小分生孢子

23. hypha conidiophore phialide conidia septa An environmental isolate of Penicillium

24. 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 ℃.

25. Culture & Colony morphology Sabouraud agar Optimal temperature 22-28℃, 37 ℃ for certain pathogenic fungi. Aerobic.

26. Unicellular fungi

27. Multicellular fungi

28. Resistance • Fungi have strong resistance to dryness, sunlight, UV light and many chemical agents, but much sensitive to heat. Usually can be killed be exposure to heat of 60°C for 1 hour.

29. Drugs • 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.

30. Fungal Infectious diseases

31. 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).

32. In general, humans have a high level of innate immunity to fungi and most of the fungal infections are mild and self-limiting. • Fungal infections are classified according to where the infections take place: A. Superficial mycoses B. Cutaneous mycoses C. Subcutaneous mycoses D. Systemic mycoses (endemic fungi and opportunistic fungi)

33. 曲霉菌 假丝酵母菌 表皮癣菌 小孢子癣菌 毛癣菌 Mucor 毛霉菌 Cryptococcus neoformans 新型隐球菌 皮炎芽生菌 荚膜组织胞浆菌 巴西副孢子菌

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

40. 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). They are a group of about 40 related fungi. • The diseases are referred to as dermatophytoses ortinea (癣病). • Dermatophytes are probably restricted to the nonviable skin because most are unable to grow at 37°C or in the presence of serum.

41. Dermatophytoses are among the most prevalent infections in the world. • Dermatophytes are classified as geophilic, zoophilic, oranthropophilic depending on whether their usual habitat is soil, animals, or humans. • Anthropophilic species cause the greatest number of human infections. They elicit relatively mild and chronic infections, produce few conidia in culture, and may be difficult to eradicate. • Geophilic and zoophilic dermatophytes, being less adapted to human hosts, produce more acute inflammatory infections that tend to resolve more quickly. Dermatophytes are acquired by contact with contaminated soil or with infected animals or humans.

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

44. common cutaneous mycoses:

46. Key concepts: superficial andcutaneous mycoses 1. Superficial and cutaneous mycoses are among the mostcommon of all communicable diseases.2. Most superficial and cutaneous fungal infections are caused by species of Malassezia, dermatophytes, or Candida.3. The growth of dermatophytes is inhibited by serum andbody temperature, and these fungi rarely become invasive.4. Geophilic and zoophilic dermatophytes usually cause acute, inflammatory lesions that respond to topical treatment within weeks and rarely recur.5. Anthropophilic dermatophytes usually cause relativelymild, chronic lesions that may require months or years oftreatment and frequently recur.

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

49. Subcutaneous mycoses • The fungi that cause subcutaneous mycoses normally reside in soil or on vegetation. They enter the skin or subcutaneous tissue by traumatic inoculation with contaminated material. • These mycoses are usually confined to the subcutaneous tissues, but in rare cases they become systemic and produce life-threatening disease.

50. Sporotrichosis • Sporotrichosis is a disease caused by the infection of the fungus Sporothrix schenckii. Because roses can spread the disease, it is one of a few diseases referred to as rose-thorn or rose-gardeners' disease. • S. schencki is naturally found in soil, hay, sphagnum moss, and plants. It enters through small cuts and abrasions in the skin. • Sporotrichosis progresses slowly - the first symptoms may appear 1 to 12 weeks (average 3 weeks) after the initial exposure to the fungus. Serious complications can also develop in patients who have a compromised immune system.