INTRODUCTION

MYCOLOGY
study of fungi, including their taxonomy, environmental impact,
and genetic and biochemical properties
MEDICAL MYCOLOGY
science devoted to the study of fungi and their relationship to
human disease
scientific discipline encompasses single-celled yeasts and
filamentous moulds as agents of disease
 Fungal agents include:
TRUE PATHOGENS
OPPORTUNISTIC PATHOGENS
TERMINOLOGIES
DEMATIACEOUS FUNGI
 fungi whose cell wall contain MELANIN, which imparts brown
to black pigment
DIMORPHIC FUNGI
fungi that have two growth forms, such as mold and yeast
which develop under different growth conditions
IMPERFECT FUNGI
fungi that lack sexual reproduction; they are represented
only by and ANAMORPH, mitotic or asexual reproductive state
PERFECT FUNGI
fungi that are capable of fungal reproduction = TELEOMORPH
POLYMORPHIC FUNGI
have more than one independent form or spore stage in their
life cycle
MOLD
hyphal or mycelial colony of growth
YEAST
unicellular, spherical to ellipsoid (3-5um) fungal cells; reproduce
by budding
EPIDEMIOLOGY
 Humans are relatively resistant to infections caused
by fungi except for DIMORPHIC FUNGI
 Major Predisposing Factors:
immunocompromised host
immunosuppressive agents or serious underlying
diseases
complex surgical procedures
antibacterial therapy
EPIDEMIOLOGY
Generally are NOT COMMUNICABLE
Humans acquire mycoses through:
Inhalation of spores
Direct contact with spores
Inoculation by trauma into the skin
FUNGI: GENERAL CHARACTERISTICS
 EUKARYOTIC
 THALLOPHYTES
have true nuclei and are heterotrophic members of the plant
family
 CHITIN in the cell wall
 ERGOSTEROL in the cell membrane
 Lack of chlorophyll
 Lack of susceptibility to antibacterial antibiotics
 SAPROPHYTIC nature
derive nutrition from organic materials
FUNGI: GENERAL CHARACTERISTICS
 Obligate aerobes
Almost all molds are aerobic
Most yeasts are facultative anaerobes
 Most are more resistant to osmotic pressure than
bacteria
 Can grow on very low moisture content
 Require less nitrogen than bacteria
 Often capable of metabolizing complex
carbohydrates, such as lignin
 Fungi vs Bacteria
Fungi Bacteria
Nucleus Defined nuclear membrane No membrane
Mitochondria Present Absent
Cell wall Glucans; mannans; chitins Peptidoglycan
Contain sterols; no respiratory
Cell membrane Sterols absent; With respiratory enzymes
enzymes
Antibiotic Resistant to penicillins, tetracycline Resistant to griseofulvin and amphotericin
susceptibility and chloramphenicol B
Dimorphism Mycelial or yeast forms none
More than one and CHON
Chromosome Only one but not CHON associated
associated
Sedimentation
80s 70s
coefficient
Cultivation < pH 6.0 pH 7.2-7.6
MORPHOLOGIC FORMS OF FUNGI
YEASTS
single vegetative cells
usually spherical or ellipsoidal (3-15um)
grows from 35°C to 37°C Cryptococcus neoformans

Colony: moist, creamy, opaque or pasty (1-3 mm)

resembling bacterial colony without aerial hyphae
identification is based primarily on biochemical testing
few divide by BINARY FISSION but most reproduce
asexually by BUDDING
 MORPHOLOGIC FORMS OF FUNGI
MOLDS
multicellular, filamentous organisms
Colony: fluffy, cottony, woolly, or powdery
grows at 25°C
Identification: growth rate, macroscopic and microscopic
appearance Rhizopus spp., showing rhizoids

Aspergillus fumigatus Rhizopus colony

 DIMORPHISM AND POLYMORPHISM
DIMORPHISM
ability of some fungi to exist in two forms, dependent on growth
conditions
 YEAST OR TISSUE STATE
organism grown at 37° C with increased CO2
 MOLD PHASE
organism grown at room temperature (22° to 25° C) in ambient air
conditions
THERMALLY DIMORPHIC FUNGI
Blastomyces dermatitidis Paracoccidioides brasiliensis
Coccidioides immitis Sporothrix schenckii Penicillium marneffei
Histoplasma capsulatum var. capsulatum
POLYMORPHIC FUNGI
both yeast and mold forms in the same culture
Example: Exophiala spp.
GENERAL MORPHOLOGIC FEATURES OF MOLDS
HYPHAE
tubular, branching filaments (2–10 m in width) of
fungal cells, mold form of growth
microscopic units of fungi
SEPTA
 cross-walls that divide hyphae
a. Septate Hyphae
 contain crosswall
b. Asseptate Hyphae or Sparsely Septate/Coenocytic
 continuous without crosswalls
Example: Zygomycetes
 Septate vs Aseptate

Phaeoacremonium sp. displaying Mucorales hyphae in tissue appears

septate hyphae sparsely septate
HYPHAE
ANTLER HYPHAE
swollen, branching tips that resemble moose antlers,
with lateral and terminal branching
Example: Trichophyton shoenleinii
RACQUET HYPHAE
contain enlarged, club-shaped areas resembling a
tennis racquet
Example: Epidermophytoc floccosum
SPIRAL HYPHAE
tightly coiled showing corkscrew-like turns
Example: Trichophyton mentagrophytes
 HYALINE vs PHAEOID
PHAEOID HYPHAE
HYALINE HYPHAE
aka DEMATIACEOUS
aka MONILIACEOUS
darkly pigmented
nonpigmented or
because of melanin in the
lightly pigmented
cell wall
pale to dark brown or
almost black

Masson-Fontana Stain
used to determine hyphal
pigmentation in tissue
stains melanin
 Phaeoid hyphae: brown
 Hyaline hyphae: pink to red
Spiral hyphae Antler hyphae Racquet hyphae
GENERAL MORPHOLOGIC FEATURES OF MOLDS
MYCELIUM
mass of intertwining structure composed of hyphae
accumulates during active growth

VEGETATIVE PORTION OR THALLUS

grows in or on a substrate and absorbs water and nutrients
anchor the colony
REPRODUCTIVE PORTION OR AERIAL
contains fruiting bodies that produce the conidia and spores
extends above the agar surface
FUNGI: Reproduction
SEXUAL REPRODUCTION
PERFECT FUNGI = TELEOMORPH
requires formation of special structures so that fertilization or
nuclear fission can occur
Meiosis  Merging of the cells  Nuclear fusion

ASEXUAL REPRODUCTION
IMPERFECT FUNGI or FUNGI IMPERFECTI = ANAMORPH
do not exhibit a sexual phase
spores are produced asexually from mycelium
Mitosis  Cytoplasmic and Nuclear Division

Note!!! SYNANOMORPHS fungi that have different asexual forms of

the same fungus (Pseudallescheria boydii)
SEXUAL SPORES
a. ASCOSPORES
contained in a saclike structure called ASCUS
following meiosis, four to eight meiospores form within an ascus
A cleistothecium of Pseudallescheria
boydii that has opened and is releasing
numerous ascospores (×750).
b. BASIDIOSPORES
contained in a club-shaped BASIDIUM
following meiosis, four meiospores usually form on the surface
of a basidium
c. ZYGOSPORES
rough-walled spores produced by the fusion of two identical
cells arising from the same hypha

Rhizopus Zygospores
d. OOSPORES
formed by heterogenous fetilization
involve the fusion of cells from separate, nonidentical hyphae
ASEXUAL SPORES
a.ARTHROCONIDIA
ARTHROSPORES
conidia that result from the simple fragmentation of hyphal cells
simplest type of sporulation
appear as square, rectangular, barrel-shaped thick-walled cells
when mature
thick walled and maybe adjacent or alternate in arrangement
Disjunctor cells empty spaces that appear between each
arthrospores in alternate arrangement
Example:
Cocciodioides immitis
Geothrichum candidum
Arthroconidia formation (A) produced
by the breaking down of a hyphal
strand (B) into individual rectangular
units (×430).
 b. BLASTOCONIDIA
BLASTOSPORES
conidial formation through a budding process
daughter cells buds off the mother cell and is pinched off
may elongate to form PSEUDOHYPHAE
Example: Candida

Cladosporium spp. showing Cladosporium type

of sporulation (arrows) with chains of elliptical
conidia (×430).
 c. CHLAMYDOCONIDIA
CHLAMYDOSPORES
large, thick-walled, usually spherical conidia
produced by “rounding-up” and enlargement of the
terminal hyphal cells
appear to be resistant resting spores
TERMINAL
form at the hyphal
tip
SESSILE
form at the hyphal
sides
INTERCALARY
form within the
Chlamydoconidia composed of thick- hyphal strand
walled spherical cells (arrows) (×430).
d. SPORANGIOSPORES
mitotic spores produced within an enclosed sporangium,
often supported by one sporangiophore (aseptate hyphae)
Example: Zygomycetes (Mucorales)

Large, saclike sporangia that contain

sporangiospores (arrow) characteristic of the
mucorales (×250).
Rhizopus spp. showing sporangium (A) on long sporangiophore (B) arising from pauciseptate
hyphae. Note the characteristic rhizoids (C) at the base of the sporangiophore (×250).
CONIDIA
asexual spores (mitospores) produced either singly or multiply
in long chains or clusters by specialized vegetative hyphae=
CONIDIOPHORES
produced either from the transformation of a vegetative
yeast or hyphal cell or from a specialized conidiogenous cell
PHIALIDES
flask-shaped secondary segments which produces the
conidia = PHIALOCONIDIA
ANNELLIDES
ringed structures that produce ANNELLOCONIDIA
CONIDIA
CONIDIOGENESIS  conidia formation

Blastic Conidiogenesis
parent cell enlarges, a septum forms and the
enlarge portion splits off to form a daughter cell

Thallic Conidiogenesis
septum forms first and new growth beyond
the septum becomes daughter cell
Conidia (asexual spores [A]) produced on In this preparation of a Trichophyton species,
specialized structures (conidiophores [B]) of the numerous, small, spherical microconidia
Aspergillus (×430). (A) are contrasted with a large, elongated
macroconidium (B) (×430).
CONIDIA
MICROCONIDIA
small, unicellular with a round,
elliptical, or pyriform shape
Sessile Microconidia
Pednculate Microconidia
MACROCONIDIA
large, usually multiseptate, and
club oval or spindle shaped
thick or thin walled
spiny (ECHINULATE) or smooth
surface
Phialoconidia
conidia that are
produced by a "vase-
shaped" conidiogenous
cell = PHIALIDE
Example: Aspergillus
Single, simple, slender, tubular conidiophore (phialide) that
produces a cluster of conidia, held together as a
gelatinous mass
Example: Acremonium
Conidiophores form a PENICILLUS that terminates in
secondary branches (metulae) and phialides, from
which chains of conidia are borne
Example: Penicillium and Paecilomyces
Flask-shaped PHIALIDES giving rise to
long chains of conidia characteristic
of Aspergilli. The basal conidia are
the youngest. Mature conidia have
rough walls. 400x.
Chain of conidia was
produced by an
ANNELLIDE
CLASSIFICATION OF FUNGI
I. Botanical Taxonomy
A. Zygomycota
B. Ascomycota
C. Basidiomycota
D. Deuteromycota
II. Type of Mycoses
A. Superficial and Cutaneous Mycoses
B. Subcutaneous Mycoses
C. Systemic Mycoses
D. Opportunistic Mycoses
I. Taxonomy of Fungi
A. Zygomycota
 include Glomeromycota and subphylum, Mucoromycotina,
and Entomophthoracortina
produce hyaline sparsely septate hyphae
Clinically important
Asexual reproduction: SPORANGIOSPORES genera:
Sexual reproduction: ZYGOSPORES  Rhizopus
 Mucor
 Rhizomucor
 Lichtheimia(formerly
Absidia)
 Cunninghamella
 B. Ascomycota
 ubiquitous in nature and produce true septate hyphae
all exhibit a sexual form (teleomorph) but also exist in
an asexual form (anamorph) Microsporum spp.
Asexual reproduction: Conidia Trichophytonspp.
Sexual reproduction: Ascospores Pseudallescheria boydii
Anamorph:
 Scedosporium
apiospermum
 Graphium

H. capsulatum
Teleomorph: Ajellomyces

Aspergillus
Scedosporium apiospermum Graphium Teleomorph: Eurotium
C. Basidiomycota
reproduce sexually through the formation of
BASIDIOSPORES
generally plant pathogens or environmental organisms
that rarely cause disease in humans
clamp connections occur at the septations in the
vegetative hyphae
Examples: smuts, rusts, mushrooms, and Cryptococcus neoformans complex

Cryptococcus neoformans var neoformans

Teleomorph: Filobasidiella neoformans
D. Deuteromycota
aka FUNGI IMPERFECTI
not a true phylogenetic group but rather an artificial
class
lack a sexual reproductive cycle
characterized by their asexual reproductive structures
= CONIDIA
most resemble Ascomyces
Examples: Epidermophyton , Sporothrix
Comparisons of the Fungal Phyla Important to Human Disease
II. Mycoses: Clinical Classification of Fungi
MYCOSES
diseases caused by fungi
categorized based on the site of the infection
A. SUPERFICIAL OR CUTANEOUS MYCOSES
fungal infections confined to the outermost layer
of skin or hair
involve the HAIR, SKIN, OR NAILS
all infect keratinized tissues
 DERMATOPHYTES
no direct invasion of the
 TINEA NIGRA
deeper tissue  TINEA VERSICOLOR
 PIEDRA
B. SUBCUTANEOUS MYCOSES
confined to the subcutaneous tissue
involve the deeper skin layers, including
muscle, connective tissue, and bone
no dissemination to distant sites

 SPOROTHRICOSIS
 MYCETOMA
 CHROMOBLASTOMYCOSIS
 PHAEOHYPHOMYCOSIS
C. SYSTEMIC MYCOSES
systemic fungal infections
primarily involve the LUNGS
disseminate and involve any organ system

Infections caused by:

 Blastomyces
 Coccidioides
 Histoplasma,
 Paracoccidioides
 P. marneffei***
D. OPPORTUNISTIC MYCOSES
infections occur primarily in patients with
some type of compromise of the immune
system
attack immunocompromised individuals

 ASPERGILLOSIS
 CANDIDIASIS
 CRYPTOCOCCOSIS
 ZYGOMYCOSIS