MLS 474 (Clinical Mycology)
OBJECTIVES
–To reveal sufficient basic science
of the medically important fungi to
assist you in diagnosing mycotic
diseases.
–To reveal sufficient clinical
knowledge to raise your index of
suspicion for mycotic diseases.
Topics
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Introduction to medical mycology
Fungal classification and Taxonomy
Antifungal Therapeutic Agents
Superficial Mycoses
Cutaneous Mycoses
Subcutaneous Mycoses
Systemic Mycoses
Fungal Allergies
Mushroom Poisoning and other Mycotoxins
INTRODUCTION
What is Mycology?
MYCOLOGY is the study of fungi
Myco- = fungi
-ology = the study of
the study of fungi, includes their genetic and
biochemical properties, their taxonomy, and
their use to humans as source for medicinals
(e.g., penicillin), food (e.g., beer, wine,
cheese, edible mushrooms), as well as their
dangers, such as poisoning or infection.
Kingdom Fungi
The characteristics of fungi
 Fungal classification
 Fungal life cycles

The Characteristics of Fungi

Body form
– unicellular
– filamentous (tubelike strands called
hypha (singular) or
hyphae (plural)
– mycelium =
aggregate of hyphae
– sclerotium =
hardened mass of
mycelium that
generally serves as
an overwintering
stage.
– fruit bodies
(mushrooms)
Hyphae
Tubular
 Hard wall of chitin
 Crosswalls may form
compartments (±
cells)
 Multinucleate
 Grow at tips

Hyphal growth
Hyphae grow from their tips
 Mycelium = extensive, feeding web of
hyphae
 Mycelia are the ecologically active bodies of
fungi

This wall is rigid
Only the tip wall is plastic and stretches
Mode of nutrition

Heterotrophic – 'other food‘
Fungi get carbon from organic sources
 Hyphal tips release enzymes
 Enzymatic breakdown of substrate
 Products diffuse back into hyphae

Nucleus hangs back
and “directs”
Product diffuses back
into hypha and is used
- Saprobes :
feed on dead tissues or organic
waste (decomposers)
Fungi as Saprobes and
Decomposers
– Symbionts :
mutually beneficial relationship
between a fungus and another
organism
Fungi as Symbionts (Mutualism)
Mycorrhizae
“Fungus roots”
 Mutualism between:

– Fungus (nutrient & water uptake for plant)
– Plant (carbohydrate for fungus)
Lichens

“Mutualism” between
– Fungus – structure
– Alga or cyanobacterium
– provides food
–Parasites :
feeding on living tissue of a host.
 Parasites that cause disease are called
pathogens.
Fungi as Parasites –Pathogens.
Fungi are Spore-ific!!!
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Spores - asexual (product of
mitosis) or sexual (product of
meiosis) in origin.
Purpose of Spores
– Allows the fungus to
move to new food source.
– Resistant stage - allows
fungus to survive periods
of adversity.
– Means of introducing new
genetic combinations into
a population
Reproduce by spores

Spores are reproductive cells
– Sexual (meiotic in origin)
– Asexual (mitotic in origin)

Formed:
– Directly on hyphae
– Inside sporangia
– Fruiting bodies
Pilobolus sporangia
Amanita fruiting body
Penicillium
hyphae with
conidia
Hyphal growth from spore
germinating
spore

mycelium
Mycelia have a huge surface area
Generalized Life Cycle of a Fungus
Definitions and Fungal
Terminology
CLINICAL MYCOLOGY:
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
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.
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).