At the end of the lesson, students will be able to:
1.
Discuss how fungi cause diseases
2.
Compare and contrast superficial, cutaneous,
subcutaneous, systemic and opportunistic
mycoses in terms of characteristics/definition,
example of diseases it may cause and its
causative agent and laboratory diagnosis
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Growth on body surfaces.
Invasion of the body.
Allergic reactions.
Toxins released after ingestion
Mycoses: fungal diseases.
Tend to be chronic because fungi grow
slowly.
Fungal diseases are classified into 4
groups:
•Superficial mycoses
•Cutaneous mycoses
•Subcutaneous mycoses
•Deep (systemic) mycoses
Superficial
Cutaneous
Definition
Infection that do not involve
a tissue response
Infections of the skin, hair &
nails
Example &
Causative
Agent
Pityriasis: dermatitis
characterized by redness of
the skin and itching caused
by Malassezia furfur
Ringworm(Tinea capitis)
Athlete’s foot(Tinea pedis)
Jock itch(Tinea cruris)
Onychomycoses (Tinea
ungium) : nail infections
caused by Candida albicans
or a dermatophytes
Lab Diagnosis Direct Microscopy: 10% KOH
is used to digest the skin
debris(bottle shaped
budding yeast cells)
PCR & other molecular
methods
Culture
SDA(Sabourauds dextrose agar
medium is used)
Creamy colonies appear
Favus: destruction of the hair
follicle caused by
Trichophyton schonleini
Direct Microscopy: septate
branched hyphae
PCR & other molecular
methods
SDA
Honey-combed like
thallus(cream colored to
Subcutaneous
Systemic
Definition
Infections beneath the skin
Infections deep within the
body
Example &
Causative
Agent
Sporotrichosis: chronic
infection of the
subcutaneous tissues and
adjacent lymphatics
characterized by nodular
lesions(Sporothrix schenkii)
Histoplasmosis (Histoplasma
capsulatum): Initial infection
in lungs. Later spreads
through blood to most
organs.
Coccidiomycosis (Coccidioides
immites): a dimorphic fungus.
Resembles tuberculosis
Lab Diagnosis Direct Microscopy: Tissue
Clinical material- Skin scrapings,
sections should be stained using sputum and bronchial washings,
Grocott's methenamine
cerebrospinal fluid, pleural fluid
silver (GMS)
and blood, bone marrow, urine
Gram stain
and tissue biopsies from various
Interpretation: Look for small
visceral organs.
narrow base budding yeast cells 2. Direct Microscopy:
Skin scrapings should be
(2-5um).
examined using 10% KOH and
Parker ink or calcofluor white
mounts.
Exudates and body fluids should
be centrifuged and the sediment
examined using either 10% KOH
FUNGAL DISEASES
Opportunistic mycoses: Caused by organisms that
are generally harmless unless individual has
weakened defenses:
◦ AIDS and cancer patients
◦ Individuals treated with broad spectrum antibiotics
◦ Very old or very young individuals (newborns).
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Examples:
◦ Aspergillosis: Inhalation of Aspergillus spores.
◦ Yeast Infections or Candidiasis: Caused mainly by Candida
albicans. Part of normal mouth, esophagus, and vaginal flora.
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Candidia albicans
◦ a common unicelluar fungus which is part of the
flora of the oral cavity, vagina, and
gastrointestinal tract;
◦ They become opportunist especially in
immunocompromised people
Oral candidiasis (Oral thrush)
Classic thrush is characterised by a white, curd-like
coating on the tongue or elsewhere in the oral
cavity. Stomatitis due to Candida is often
associated with painful infection of the lips - and
corners of the mouth.
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Genital or perigenital candidiasis ((vulvo vaginitis)
(vulvo)vaginitis due to Candida .
Contamination of the vagina with Candida stems from
the endogenous endosaprophytic flora of the gastrointestinal tract.
Diagnoses
◦ in culture, it grows as blastospores, pseudohyphae,
and septate hyphae
◦ candidiasis
the collective term for infection
involving Candida
 cutaneous
 vaginal
 systemic