MLS 474 (Clinical Mycology)MLS 474 (Clinical Mycology)

– To reveal sufficient To reveal sufficient basic basic sciencescience of the medically of the medically important fungi to assist you in important fungi to assist you in diagnosing mycotic diseases.diagnosing mycotic diseases.

– To reveal sufficient To reveal sufficient clinical clinical knowledgeknowledge to raise your index to raise your index of suspicion for mycotic of suspicion for mycotic diseases. diseases.

OBJECTIVESOBJECTIVES

Introduction to medical mycologyIntroduction to medical mycology Fungal classification and TaxonomyFungal classification and Taxonomy Antifungal Therapeutic AgentsAntifungal Therapeutic Agents Superficial MycosesSuperficial Mycoses Cutaneous Mycoses Cutaneous Mycoses Subcutaneous MycosesSubcutaneous Mycoses Systemic Mycoses Systemic Mycoses Fungal AllergiesFungal Allergies Mushroom Poisoning and other Mushroom Poisoning and other MycotoxinsMycotoxins

TopicsTopics

INTRODUCTIONINTRODUCTION

the study of fungi, includes their genetic the study of fungi, includes their genetic and biochemical properties, their and biochemical properties, their taxonomy, and their use to humans as taxonomy, and their use to humans as source for medicinals (e.g., penicillin), source for medicinals (e.g., penicillin), food (e.g., beer, wine, cheese, edible food (e.g., beer, wine, cheese, edible mushrooms), as well as their dangers, mushrooms), as well as their dangers, such as poisoning or infection.such as poisoning or infection.

What is What is MycologyMycology??

MYCOLOGY is the study of fungi Myco- = fungi -ology = the study of

Kingdom FungiKingdom Fungi

The characteristics of fungiThe characteristics of fungi Fungal classificationFungal classification Fungal life cyclesFungal life cycles

The Characteristics of The Characteristics of FungiFungi Body form Body form

– unicellular unicellular – filamentous (tube-filamentous (tube-

like strands called like strands called hypha (singular) or hypha (singular) or hyphae (plural) hyphae (plural)

– mycelium = mycelium = aggregate of aggregate of hyphae hyphae

– sclerotium = sclerotium = hardened mass of hardened mass of mycelium that mycelium that generally serves as generally serves as an overwintering an overwintering stage. stage.

– fruit bodies fruit bodies (mushrooms) (mushrooms)

TubularTubular Hard wall of chitinHard wall of chitin Crosswalls may Crosswalls may

form compartments form compartments ((± ± cells)cells)

MultinucleateMultinucleate Grow at tipsGrow at tips

HyphaeHyphae

Hyphal growthHyphal growth Hyphae grow from their tipsHyphae grow from their tips Mycelium = extensive, feeding web of Mycelium = extensive, feeding web of

hyphaehyphae Mycelia are the ecologically active Mycelia are the ecologically active

bodies of fungibodies of fungi

This wall is rigid Only the tip wall is plastic and stretches

Mode of nutritionMode of nutrition

Fungi get carbon from organic sourcesFungi get carbon from organic sources Hyphal tips release enzymesHyphal tips release enzymes Enzymatic breakdown of substrateEnzymatic breakdown of substrate Products diffuse back into hyphaeProducts diffuse back into hyphae

Product diffuses backinto hypha and is used

Nucleus hangs backand “directs”

Heterotrophic – 'other Heterotrophic – 'other food‘ food‘

- Saprobes :- Saprobes : feed on dead tissues or feed on dead tissues or

organic waste (decomposers)organic waste (decomposers)

Fungi as Saprobes and Fungi as Saprobes and DecomposersDecomposers

– SymbiontsSymbionts : :

mutually beneficial mutually beneficial relationship between a relationship between a fungus and another organismfungus and another organism

Fungi as Symbionts Fungi as Symbionts (Mutualism)(Mutualism)

MycorrhizaeMycorrhizae

““Fungus roots”Fungus roots” Mutualism between:Mutualism between:

– Fungus (nutrient & water uptake for plant)Fungus (nutrient & water uptake for plant)– Plant (carbohydrate for fungus)Plant (carbohydrate for fungus)

LichensLichens

““Mutualism” betweenMutualism” between– Fungus – structureFungus – structure– Alga or Alga or

cyanobacterium – cyanobacterium – provides foodprovides food

–Parasites :Parasites : feeding on living tissue of a feeding on living tissue of a host.host.    Parasites that cause disease are Parasites that cause disease are called pathogens. called pathogens.

Fungi as Parasites –PathogensFungi as Parasites –Pathogens..

Fungi are Spore-ificFungi are Spore-ific!!!!!!

Spores - asexual (product of Spores - asexual (product of mitosis) or sexual (product mitosis) or sexual (product of meiosis) in origin. of meiosis) in origin.

Purpose of Spores Purpose of Spores – Allows the fungus to Allows the fungus to

move to new food source. move to new food source. – Resistant stage - allows Resistant stage - allows

fungus to survive periods fungus to survive periods of adversity.of adversity.

– Means of introducing new Means of introducing new genetic combinations into genetic combinations into a populationa population

Reproduce by sporesReproduce by spores Spores are reproductive cellsSpores are reproductive cells

– Sexual (meiotic in origin)Sexual (meiotic in origin)– Asexual (mitotic in origin)Asexual (mitotic in origin)

Formed:Formed:– Directly on hyphaeDirectly on hyphae– Inside sporangiaInside sporangia– Fruiting bodies Fruiting bodies

Amanita fruiting body

Pilobolus sporangia

Penicillium hyphae with

conidia

Hyphal growth from sporeHyphal growth from spore

myceliumgerminatingspore

Mycelia have a huge surface areaMycelia have a huge surface area

Generalized Life Cycle of a Generalized Life Cycle of a FungusFungus

Definitions and Fungal Definitions and Fungal TerminologyTerminology

CLINICAL MYCOLOGY:CLINICAL MYCOLOGY: Remains more of a descriptive art than an analytical science.Remains more of a descriptive art than an analytical science.

Mold (sometimes spelled ‘mould’): is a morphological term referring to a filamentous (multicellular) fungus.

Yeast is a morphological term referring to a unicellular fungus.

DIMORPHIC FUNGI: This class of fungi is characterized by two forms of growth:1. Growth as a mold with septate hyphae in their natural reservoir (e.g. soil) or when incubated at 25° C. on conventional fungal media (Sabouraud dextrose or potato dextrose agars).2. Growth as a yeast in the tissues of an animal/person or when incubated at 37° on enriched media (Brain heart infusion agar).

A hypha (plural hyphae) is a long, branching filamentous cell. hyphae are the main mode of vegetative growth, and are collectively called a mycelium.

Mycelium: the intertwined mass of hyphae that forms the mold colony. The vegetative mycelium is composed of those hyphae that adhere to the substrate and absorbs nutrients. The aerial mycelium is composed of those hyphae that grow up from the surface and support the spores.

Septate: Cross-walls (septae) that divide hyphae into segments. If there are few or no cross-walls the hyphae are considered to be aseptate.

Conidia (singular = conidium): asexual spores borne externally on hyphae or on a conidiophore.

Conidiophore: the specialized hyphal stalk on which conidia develop either singly or in Clusters.

Conidia

Conidiophore

Sporangia (singular = sporangium): spherical sack within which asexual spores (sporangiospores) form by progressive cytoplasmic cleavage.

Sporangiophore - specialized hyphal stalk which bears sporangia.

Sporangiospores: small spores contained within sporangia.

Sporangiospores

Sporangium

Sporangiophore

Rhizoid: rootlike branched hyphae which anchor the mycelium to the substrate; characteristic of certain Zygomycetes (Rhizopus and Absidium).

Dematiaceous Molds: the term dematiaceous refers to molds whose hyphae are pigmented. Because of the pigment, the colonies of these fungi will appear dark green, brown, or black on both the top and reverse (underside).

Germ-tube: The initial hyphal outgrowth of a germinating spore or yeast; especially important for identification of Candida albicans.

Pseudohyphae (or Pseudomycelium): chains of successively budding yeast cells that have complete cell walls, but have not detached from one another.