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What diseases do yeasts and molds cause?

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Presentation on theme: "What diseases do yeasts and molds cause?"— Presentation transcript:

1 What diseases do yeasts and molds cause?
Mycology What diseases do yeasts and molds cause?

2 Mycology Mycology is the study of fungi which includes yeast and molds
They are eukaryotic and are chemo-heterotrophs (require organic compounds for energy and a carbon source) Most have a cell wall of chitin Molds are made of long filaments called hyphae If there are cross walls that divide the hyphae into uninucleate units the hyphae are septate hyphae If there are no cross walls, the hyphae are called non-septate or coenocytic hyphae When the hyphae grow and intertwine to form a mass, they are called mycelium

3 Mycology The portion of mycelium concerned with obtaining nutrients is called the vegetative mycelium The portion concerned with reproduction is called aerial mycelium because it usually projects above the surface of the vegetative mycelium Yeasts are non-filamentous, unicellular fungi that are oval or spherical in shape. Yeasts reproduce by the process of budding

4 Mycology Dimorphic fungi
When the buds fail to detach from each other, pseudohyphae are seen Dimorphic fungi Some fungi, including most of the pathogenic fungi, exhibit two forms of growth. This is known as dimorphism and the organisms can grow either as a yeast-like form or a mold-like form. Frequently the form that the organism grows as is temperature dependent and at 370 C the organism grows as a yeast-like form and at RT it grows in a mold-like form. CO2 concentration or the presence of serum may also be a determining factor How is the dimorphism of Candida albicans different from that described above?

5 Mycology How do we identify molds in the lab?
Based on type of hyphae (septate versus non-septate) Based on color of mycelium Based on reproductive structures Molds may form either sexual or asexual spores Sexual spores are formed from the fusion of nuclei from two opposite mating strains of the same species. They are only formed under special conditions, but they are used to classify fungi (more on this later) Asexual spores, which are most commonly used in identification, are formed by the aerial mycelium of a single organism by mitosis and cell division

6 Arthrospores Arthrospores are formed by the fragmentation of septate hyphae

7 Mycology Chlamydospores are thick walled spores formed within a hyphae

8 Mycology Sporangiospores are formed within a sac (sporangium) at the end of an aerial hyphae called a sporangiophore

9 Sporangiospores

10 Mycology Conidiospores are produced in a chain at the end of a conidiophore. Unicellular conidiospores are called microconidia

11 Microconidia

12 Mycology Multicelled conidiospores are called macroconidia

13 Macroconidia

14 Mycology Blastospores consist of a bud coming off the parental cell

15 Mycology Fungi are classified based on the type of sexual spore that they form Zygomycota Have non-septate hyphea Have asexual sporangiospores Form sexual zygospores. They are large spores enclosed in a thick wall and formed from the fusion of two cells

16 Zygospores

17 Mycology Ascomycota Have septate hyphae Have asexual conidiospores
Have sexual ascospores. Ascospores result from the fusion of nuclei of two cells. They are produced in a sac-like structure called an ascus.

18 Ascospores inside an ascus

19 Mycology Basidiomycota Have septate hyphae Have asexual conidiospores
Have sexual basidiospores. Basidiospores are formed externally on a base pedestal called a basidium

20 Basidiospores

21 Mycology Fungal diseases – any fungal infection is called a mycosis. Mycoses are classified into five groups based on the mode of entry and the level of infective tissue: Systemic mycosis – is a fungal infection deep within the patient Can involve a number of tissues and organs Usually caused by saprophytic fungi that live in the soil The route of transmission is via inhalation of spores. Therefore the infection usually begins in the lungs and then spreads to other tissues The diseases often resemble tuberculosis The infections are not contagious

22 Mycology Examples of systemic mycoses include Coccidioidomycosis (San Joaquin Valley Fever)– caused by Coccidiodes immitis Histoplasmosis – caused by Histoplasma capsulatum Blastomycosis – caused by Blastomyces dermatitidis Subcutaneous mycoses (mycetoma) - are fungal infections beneath the skin They are caused by fungi that live in soil and vegetation Infection occurs when spores or hyphae are planted directly into a puncture wound The infections are not contagious Examples of subcutaneous mycoses include Chromomycosis – caused by Phialophora or Fonsecae Maduramycosis – caused by Allescheria boydii

23 Mycetoma

24 Mycology Cutaneous mycoses (ringworm) – are fungal infections of the hair, epidermis, and nails Are caused by fungi known as dermatophytes (dermatomycosis) which secrete the enzyme keratinase which digests keratin, a protein found in hair, skin, and nails. Infection is from person to person or animal to person by contact with infected hair or epidermis. Tinea capitis is a scalp and hair infection Tinea pedis is a foot infection infection (athlete’s foot) Tinea unguium is an infection of the nails Microsporum, Trichophyton, and Epidermophyton are the causative agents

25 Cutaneous mycoses

26 Mycology Superficial mycoses – are fungal infections localized to the hair shafts and superficial epidermal cells Is spread by direct contact with infected hair or skin Examples are White piedra in which white balls are found on the hair shafts is caused by Trichosporon Black piedra is caused by Piedra ishortae Tinea nigra in white black spots are seen on the skin is caused by Cladosporium werneckii

27 Black piedra

28 Mycology Opportunistic mycoses – caused by a pathogen that is generally harmless in its normal habitat (includes normal flora), but can become pathogenic in a debilitated or traumatized host Mucormycosis – caused by Rhizopus or Mucor in patients with ketoacidosis Aspergillosis – caused after inhalation of Aspergillus spores in those with lung disease or cancer Candidiasis – caused by Candida albicans. Vulvovaginal candidiasis often occurs following antibiotic therapy Thrush is an infection of the mouth and throat

29 Thrush

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