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    BASIC MYCOLOGYMICROBIOLOGY LECTURE SERIES LUZ GREGORIA VELA

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    FUNGI

    Eukaryotic; most are nonmotile and possess a rigid wall

    Nonphotosynthetic

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    FUNGI

    Each fungal cell has at least one nucleus with a nuclear mem

    mitochondria and secretory apparatus

    Most are obligate or facultative aerobes

    Chemotrophic

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    MYCOSES

    Fungal infections

    Most pathogenic fungi are exogenous

    Highest incidence: candidiasis, dermatophytosis

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    MAJOR MYCOSES

    CATEGORY MYCOSIS CAUSATIVEAGEN

    Superficial Pityriasis versicolor

    Tinia nigraWhite piedra

    Black piedra

    Malassezia specie

    Hortaea werneck

    Trichosporon sp.

    Piedraia hortaeCutaneous Dermatophytosis

    Candidiasis of skin,

    mucosa or nails

    Microsporum spec

    Trichophyton spec

    Epidermophyton f

    Candida albicans

    Candida species

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    MAJOR MYCOSES

    CATEGORY MYCOSIS CAUSATIVEAGEN

    Endemic

    (primary,

    systemic)

    Sporotrichosis

    Chromoblastomycosis

    Mycetoma

    Phaeohyphomycosis

    Sporothrix schenc

    Phialophora verru

    Fonsecaea pedros

    Pseudallescheria bModurella myceto

    others

    Exophiala, Bipolar

    and other demat

    molds

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    MAJOR MYCOSES

    CATEGORY MYCOSIS CAUSATIVEAGEN

    Opportunistic Systemic candidiasis

    Cryptococcosis

    Aspergillosis

    Hyalohyphomycosis

    Candida albicans

    Candida species

    Cryptococcus neo

    Cryptococcus gattAspergillus fumiga

    Aspergillus specie

    Species of FusariuPaecilomyces, Trich

    other hyaline mo

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    MAJOR MYCOSES

    CATEGORY MYCOSIS CAUSATIVEAGEN

    Opportunistic Phaeohyphomycosis

    Mucormycosis

    (zygomycosis)

    Chladophialophor

    species ofAlterna

    Cladosporium, Bip

    Exserohilum and odematiaceous mSpecies of Rhizop

    Lichtheimia, Cunn

    other zygomycet

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    MAJOR MYCOSES

    CATEGORY MYCOSIS CAUSATIVEAGEN

    Opportunistic Pneumocystis pneumoniaPenicillosis

    Pneumocystis jirov

    Penicillum marnef

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    GENERAL PROPERTIES AND CLASSIFICATIO

    FUNGI

    Fungi grow in two basic forms:1. YEASTS- grow as single cells that reproduce by asexual

    2. MOLDS- production of multicellular filamentous colonie

    branching cylindric tubules (hyphae) 2-10 mm

    mycelium- mass of intertwined hyphae that accumuactive growth

    some hyphae are divided into cells by cross-walls (septypically form at regular intervals during hyphal gro

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    GENERAL PROPERTIES AND CLASSIFICATIO

    FUNGI

    A - coenocy

    B - septate

    C - septum

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    GENERAL PROPERTIES AND CLASSIFICATIO

    FUNGI

    Vegetative or substrate hyphae penetrate the surroundmedium, anchor the colony and absorb the nutrients

    Aerial hyphae project above the surface of the mycelium;bear the reproductive structures of the mold

    When a mold is isolated from a clinical specimen, itsgrowth ratemacroscopic appearance and microscopic morphology a

    sufficient to determine its genus and species

    Most helpful phenotypic features: ontogeny and morphology o

    asexual reproductive spores or conidia

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    HYPHAE

    Coenocytic /aseptate vs.

    Septate

    Hyaline vs.

    dematiaceous

    Fine vs. broad

    non

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    GENERAL PROPERTIES AND CLASSIFICATIO

    FUNGI

    CONIDIA asexual reproductive spores (MITOSPORES) produc

    from the transformation of a vegetative yeast or hyphal cell or from

    specialized conidiogenous cell, which may be simple or complex an

    May be formed on specialized hyphae (conidiophores)

    MICROCONIDIA small

    MACROCONIDIA large or multicellular

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    Microconidia

    Singly or in clusters

    Macroconidia

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    GENERAL PROPERTIES AND CLASSIFICATIO

    FUNGI

    YEASTS single cells, usually spherical to ellipsoid in shape,

    Most reproduce by budding

    Some produce buds that characteristically fail to detach and become

    (pseudohyphae chain of elongated yeast cells) Colonies usually soft, opaque, 1-3 mm in size, cream-colored

    Yeast species are identified on the basis ofphysiologic tests, and a

    morphologic differences

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    YEAST CELLS

    Budding yeast

    cells surrounded

    by clear capsules

    encapsulated sphe

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    broad based bud

    cigar to oval shaped yeast ce

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    GENERAL PROPERTIES AND CLASSIFICATIO

    FUNGI

    Thermally dimorphic (form different structures at different te

    Essential rigid cell wall (determines shape and protects from

    and environmental stress)

    Composed largely of carbohydrate layers (long chains of polysaccharglycoproteins and lipids

    Sugar polymers: Chitin (b-1,4-linked N- acetylglucosamine),glucans (b1,6-glucan, mannans (polymers of mannose-a-1,6-mannose)

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    GENERAL PROPERTIES AND CLASSIFICATIO

    FUNGI

    Essential rigid cell wall

    During infection, fungal cell walls exert important pathobiologic properties-

    surface component mediate attachment to host cells

    bind to pattern recognition receptors on host cell membranes

    cell wall glucans and other polysaccharides activate the complemen

    provoke an inflammatory reactionrelease immunodominant antigens that may elicit cellular immune r

    diagnostic antibodies

    dematiaceous brown or black pigment to the fungal colony (me

    walls)

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    GENERAL PROPERTIES AND CLASSIFICATIO

    FUNGI

    Most fungi are obligate aerobes, some are facultative anaernone are obligate aerobes

    All fungi require a preformed organic source of carbon

    Natural habitat of most fungi: environment, except Candida alwhich is part of the normal human flora

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    GENERAL PROPERTIES AND CLASSIFICATIO

    FUNGI

    FEATURE FUNGI BACTERIA

    Diameter Approximately 4mm (Candida) Approximately 1m(Staphylococcus)

    Nucleus Eukaryotic Prokaryotic

    Cytoplasm Mitochondria & ER present Mitochondria & ERCell Membrane Sterols present Sterols absent (ex

    Mycoplasma)

    Cell Wall Content Chitin Peptidoglycan

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    GENERAL PROPERTIES AND CLASSIFICATIO

    FUNGI

    FEATURE FUNGI BACTERIA

    Spores Sexual and asexual spores for

    reproduction

    Endospores for su

    reproduction

    Thermal Dimorphism Yes (some) No

    Metabolism Require organis carbon, noobligates anaerobes Many do not requcarbon, many oblig

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    CLASSIFICATION ACCORDING TO COLONY TYPE A

    DIFFERENT TEMPERATURES

    MONOMORPHIC OR MONOPHASIC produce one

    colony at both room and incubation temperature

    Ex. Cryptococcus neoformans yeast only

    Aspergillus species filamentous only

    Candida albicans yeastlike colony

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    COLONIES PRODUCED BY FUNGI

    YEAST COLON

    soft, pasty type o

    yeast produced by fremains at yeast for

    4o

    C and 37o

    C

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    COLONIES PRODUCED BY FUNGI

    YEASTLIKE COLON soft, pasty type of colo

    produced by fungi which

    ability to form pseudom(false hypha)

    - Pseudohypha consiselongated buds remainin

    to the parent cell despit

    division.

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    COLONIES PRODUCED BY FUNGI

    FILAMENTOUS OR MOLD

    COLONY

    a mold type of colony with an

    aerial mycelium that appears

    cottony, wooly, powdery orgranular.- true mycelia are produced by

    spores which germinate to formbranching hyphae

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    CRYPTOCOCCUS NEOFORMANS

    Off white, mucous colonies on Sabourauds medium after 5

    ROOM TEMPERATURE

    CULTURE

    37oC

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    ASPERGILLUS SPP.

    Green colony after 5 to 10 days on Sabouraud medium. Color

    ROOM TEMPERATURE

    CULTURE

    37oC

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    CANDIDA ALBICANS

    White colonies incubated on Sabouraud medium for 5 to 7 day

    ROOM TEMPERATURE

    CULTURE

    37oC

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    CLASSIFICATION ACCORDING TO COLONY TYPE A

    DIFFERENT TEMPERATURES

    DIMORPHIC OR DIPHASIC produce a yeast-like colo

    or incubation temperature (YEAST PHASE) and a filamentou

    colony at room temperature (MYCELIAL PHASE)

    Ex. Sporothrix schenckii

    Histoplasma capsulatum

    Blastomyces dermatitidis

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    SPOROTHRIX SCHENCKII

    ROOM TEMPCULTURE

    Dark, greasy-looking culture after 1 to 2

    weeks incubation on Sabouraud medium

    White to tan yeast colonies af

    incubation on brain heart infus

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    HISTOPLASMA CAPSULATUM

    ROOM TEMPCULTURE

    37oC

    White, innocent looking(but dangerous)colony after 1 to 3 weeks incubation on

    Saboraud medium.

    White to tan yeast colony afte

    incubation on brain heart infus

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    BLASTOMYCES DERMATITIDIS

    ROOM TEMPCULTURE

    37oC

    Colony after 1 to 3 weeks incubation onSabouraud medium. white colony, brown to

    tan underside

    Rough, dry, heaped-up yeast c

    3 weeks incubation on brain

    agar

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    TAXONOMY

    PHYLUM GLOMERULOMYCOTA, ORDER MUCOR

    PHYLUM ASCOMYCOTA (Ascomycetes)

    65% of the known fungi, 85% of the human pathogens PHYLUM BASIDIOMYCOTA (Basidiomycetes)

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    TAXONOMY

    PHYLUM GLOMERULOMYCOTA, ORDER MUCORALE

    Sexual reproduction results in aZYGOSPORE; asexual reproductio

    SPORANGIA

    Vegetative hyphae sparsely septate

    Rhizopus, Lichtheimia, Mucor, Cunninghamella

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    TAXONOMY

    PHYLUM ASCOMYCOTA (Ascomycetes) Sexual reproduction involves a sac (ascus) in which karyogamy and

    occurs ASCOSPORES; asexual reproduction occurs via CONID

    (+) septate hyphae

    Yeasts (Saccharomyces, Candida); molds (Coccidioides, Blastomyces, T

    PHYLUM BASIDIOMYCOTA (Basidiomycetes)

    Sexual reproduction results in dikaryotic hyphae and 4 progeny

    BASIDIOSPORES supported by a club-shaped basidium; no asexu

    Hyphae with complex septa; Mushrooms, Cryptococcus

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    DIAGNOSIS

    Species of a clinical isolate can be identified by molecular or p

    methods (signature DNA sequences, morphology of reprodu

    structures, physiologic properties)

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    1. zygospores single large spores with thick walls

    2. ascospores formed in a sac (ascus)

    3. basidiospores formed externally on a tip of a pedestal (

    FUNGI IMPERFECTI - Fungi that do not form sexual spores

    imperfect

    SEXUAL SPORES:

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    ASCOSPOproduced w

    enlarged cenuclear fusi

    in a sac call

    ASCUS orASCOCA

    Typically, th

    4-8 spores

    ascus.

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    ASCOCAASCOSPORES

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    ASEXUAL SPORES

    arise by the differentiation of spore bearing hyphae without

    most fungi of medical interest propagate asexually by forming

    spores (conidia) from the sides or ends of specialized struct

    1. arthrospores2. chlamydospores

    3. blastospores

    4. sporangiospores

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    ARTHROSPORES fragmentation or segmentation omycelium results in the production of rectangular, thick-w

    spores which are uniformly sized

    Ex. Geotrichum

    Coccidioides immitis

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    Arthroconidia

    formation

    (A) produced by the

    breaking down of a hyphal

    strand(B) into individualrectangular units.

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    CHLAMYDOSPORES large, round, thick-walled re

    a septate hypha or at the terminal ends; formed when t

    cytoplasm of these hypha become concentrated and en

    diameter greater than that of the rest of the hypha; may

    intercalary, terminal or lateral.

    Ex. Candida albicans

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    CHLAMYDOSPORES

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    BLASTOS

    formed by a

    budding pro

    cells of the m

    Budding may

    1)one cell to

    basis

    Blastomyces2) multispor

    Paracoccidioi

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    SPORANGIOSproduced on a sp

    hypha, inside a ro

    container known

    SPORANGIUM

    When the sporangium ruptures, the sporangiospores scatter athin walled sporangium in place or it may dissolve

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    GROWTH AND ISOLATION OF FUNGI

    Saborauds agar traditional mycological medium

    Contains glucose and modified peptone (pH 7.0)

    Does not readily support the growth of bacteria

    Inhibitory mold agar

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    MYCOTOXINS

    Poisonous substances produced by fungi

    Cause acute or chronic intoxication and damage

    Produced by mushrooms (Amanita sp.) mycetismus

    AflatoxinAspergillus flavus

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    ANTIFUNGAL THERAPY

    POLYENES Amphotericin B, Nystatin Bind to ergosterol in the cell membrane

    FLUCYTOSINEpyrimidine analog

    AZOLES interfere with the synthesis of ergosterol

    ECHINOCANDINS inhibit the synthesis of cell wall b-gl

    GRISEOFULVIN interferes with microtubule assembly

    TERBINAFINE allylamine drug; blocks ergosterol syntheinhibiting squalene epoxidase

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    CONIDIA ACCORDING TO SHAPE

    FUSIFORM spindle-shaped

    CLAVATE club-shaped

    MURIFORM multiseptate, both transverse and lo

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    CONIDIA ACCORDING TO ARRANGEME

    SESSILE AND LATERAL - develops directly on th

    the hypha with no conidiophore or stem

    EN GRAPPE - clustered

    PEDUNCULATE - develop from the end of a shortconidiophore