Introduction To Medical Mycology

Lecture one

Introduction to Medical Mycology

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

mold yeast

fungi

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 motile  reproduce by spores  form mold or yeast  depending on fungal species  growth 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

Morphology of Dimorphic fungi

Histoplasma

Paracoccidiodes

Coccidiodes

Chromoblastomycosis Blastomycosis

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

Basidiospores

Ascospores

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