Introduction to Medical Mycology

Introduction to Medical Mycology

Lecture one

Definition

Eukaryotic Initiate disease in human and animals Yeast or mold or both

fungi

mold

yeast

Disadvantage and advantage

Over 400,000 species 150 species cause disease Other non pathogenic species emerged Food spoilage Plant disease, destroy tumber, textile Decay plant and animals in soil Production of antibiotics Organic acids, soya sauce Genetic and biochemical scientific model

Habitat

free living few are normal flora infection originated from exogenous traumatic or inhalation don't contain chlorophyll can’t synthesize macromolecules from CO2 lead a heterotrophic existing saprobes, symbionts, commensal, parasites

Pathogenicity of fungi

A bunch of fungi can cause disease due to ability to adapt to host tissues dermatophytes (metabolize keratin) systemic fungi grow at 37Ć and survive at low oxidation reduction state some fungi have capsule

Structure of fungi

Cell wall chitin and glucan Plasma membrane ergosterol Nucleus Double membrane with pores rich in RNA Cytoplasm mitochondria, vacules and so on

Morphology of fungi

Eukaryotic non motilereproduce by sporesform mold or yeast depending on fungal speciesgrowth condition

Mold form

spore germinate Filament (hyphae) Divide by septa Uni or multinucleated Some fungi have no septa (Coenocytic hyphae) Zygomycota

Mycelium A mass of hyphae Aerial mycelium Submerged mycelium

Types of septa

Simple solid plate with out pores With single pores With several pores (sieve-like appearance) Ascomycota and Deuteromycota Barrel shaped apparatus called dolipore Hook-like bridge between cells (clamp-connection) Basidiomycota Mycelium arrangement Simple Form complex tissue Hyphae loss its individuality Take column, rope, ball and other forms

Types of Septa

Yeast form

Spore germinate Oval, round, elongated single cell Reproduce by budding Some by fission Moist or mucoid colonies Pseudohyphae True hyphae Depend on growth condition and species

Dimorphic fungi

Important mycotic agents Yeast form in host tissue (37Ć) or in vivo Mold or mycelium in 25Ć or environment Histoplasma capsulatum, Sporothrix schenckii Some have spherules with endospores Coccidiodes immitis Some produce sclerotia bodies (chromo-) Some produce tick conidia (adiaspore) Never reproduce inside host Emmonisa parva

HistoplasmaParacoccidiodes

Chromoblastomycosis

Blastomycosis

Coccidiodes

Morphology of Dimorphic fungi

Growth

Mycelium Grow equally in all direction Circular colony in solid medium Globose colony in liquid medium Most fungi grow at 25Ć Some are grow at 37-50Ć Aspergillus fumigatus, Cladosporium trichoides PH 6.6 to 6.8

Nutritional requirements

Absorb rather than digest Require organic compounds Facultative parasites Few are obligate parasites Rhinosporidium seeberi Loboa loboi Carbohydrates (glucose) Organic or inorganic nitrogen (ammonium

compounds) Some require vitamins (anthropophilic

dermatophytes)

Reproduction

Asexual (anamorphic state) In filaments fungi Free cell formation inside sporangium Zygomycota Zygospores Budding out as new structure Fragmentation of the fertile hyphae Conidia (Ascomycota and Basidiomycota,

Deuteromycota Pattern of conidia Thallic conidia produce from entire parent cell Blastic conidia from part of parent cell

Asexual reproduction in mold form

Yeast

Asexual reproduction Budding such as candida species Fission such as Pencillium marneffei

Sexual reproduction (Teleomorph state) Zygomycota, Ascomycota and Basidiomycota Based on fruiting structure Fungi lacking sexual stage Deuteromycota (Fungi imperfectii)

Types of sexual reproduction

Homothallic Thallus is self-fertile Heterothallic Thallus is self-sterile Stages of sexual reproduction Plasmokamy Karyokamy Meiosis Formation of diploid nucleus Mitosis to form haploid nucleus Sexual spores

Sexual reproduction in Zygomycota

Sexual spores

Remain attach to hyphae Zygospores (Zygomycota) Rhizopus, Mucor and Absidia Remain in side sac called ascospores (Ascomycota) Histoplasma, Dermatophytes, Peidraia hortae Spore reside on basidium called basidiospores Basidiomycota Cryptococcus neoformans

Types of Sexual spores

zygospore

BasidiosporesAscospores

Phylum of Deuteromycota

Lacking sexual phase Candida species, Malassezia furfue Epidermophyton floccosum, American coccidiodes Classification or taxonomy of fungi Basic rank is species Grouped in system of genera Families, classes, phyla or division Kingdom Varieties

Filobasidiella neoformans

Sexual stage of Cryptococcus neoformans Kingdom Fungi Phylum Basidiomycota Class Heterobasidiomycetes Order Filobasidiales Genera Species Varieties