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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