PATHOGENIC
FUNGI
Medical mycology
• field of medicine concerned with
the diagnosis, managements and
prevention of mycoses
MYCOSES
• diseases caused by fungi
• Mode of infection:
–
–
–
–
Inhalation
Trauma
Ingestion
Rarely from person to person
• Most mycoses are not contagious
Clinical Manifestations
of Mycoses
• Fungal infections (most common)
• Toxicoses (poisoning)
• Allergies (hypersensitivity reactions)
DIAGNOSIS
DIAGNOSIS
• Sabourad dextrose agar – the medium
where fungi is cultured
• Potassium hydroxide (KOH) preparations –
dissolve keratin in skin scrapings or biopsy
specimens, leaving only fungal cells for
examination
• Gomori methenamine silver (GMS) stain –
used on tissue to stain fungal cells black
• Direct immunofluorescence - labeling of
antibodies or antigens with fluorescent dyes.
Mycoses are also among
the most difficult diseases
to heal.
WHY?
•
Fungi possess the biochemical ability to
resist the oxidative damage
perpetuated by T cells during cellmediated immune response
•
Fungi are eukaryotic and thus
biochemically similar to human cells,
which means most fungicides are toxic
to human tissues
The Gold Standard!!!
• Amphotericin B – considered the
best drug for treating systemic
mycoses and other fungal infections
that do not respond to other drugs
The downside…..
It is still toxic to humans
The alternative..
• Azole drugs
– which only inhibit the fungi (fungistatic)
rather than kill it
– less toxic to humans
– e.g. ketoconazole, itraconazole and
fluconazole
Categories of Fungal
Agents
• True fungal pathogens
• Opportunistic fungi
True pathogens
• Have the ability to actively attack
and invade tissues
• Can infect any host, regardless of its
immune status
Opportunistic Fungi
• Lack genes for proteins that aid in
colonizing the body
• Do not cause disease in healthy
individuals
• Can infect only susceptible
individuals, those whose body’s
defenses are low
The only fungi known to cause disease in
humans:
•
•
•
•
Blastomyces dermatiditis
Coccidiodes immitis
Histoplasma capsulatum
Paracoccidiodes brasiliensis
The remaining fungi that cause disease are
considered opportunistic fungi.
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SYSTEMIC MYCOSIS
caused by TRUE PATHOGENS
SYSTEMIC MYCOSES
•those fungal infections that spread
throughout the body
•result of infections by one of the four
pathogenic, dimorphic fungi of the division
Ascomycota.
• Ascomycota: Blastomyces, Coccidioides,
Histoplasma, and Paracocidioides
BLASTOMYCOSIS
BLASTOMYCOSIS
•
Pathogen: Blastomyces dermatitidis.
•
B. dermatitidis normally grows in soil rich in
organic material, such as decaying
vegetation and animal wastes, where
cool, damp conditions favor growth and
sporulation.
BLASTOMYCOSIS
•
Mode of infection: Inhalation of dust
disturbed from the environmental
sources carries fungal spores and
pieces of hyphae into the lungs.
BLASTOMYCOSIS
•
Pulmonary Blastomycosis – the most
common manifestation of Blastomyces
infection in humans.
•
Initial pulmonary lesions are asymptomatic.
•
If symptoms do develop, they are vague
and include cough, fever, malaise, and
weight loss.
BLASTOMYCOSIS
•
Cutaneous blastomycosis – consists of
generally painless lesions on the face
and upper body.
•
Can be raised and wartlike, craterlike
due to the death of tissue.
BLASTOMYCOSIS
•
Osteoarticular blastomycosis – a
condition where fungus spreads to the
spine, pelvis, cranium, ribs, long bones,
or subcutaneous tissues surrounding
joints.
•Patients
with Cutaneous blastomycosis • painless lesions on the face and upper body.
BLASTOMYCOSIS
•
Diagnosis – relies on identification of B.
dermatitis following culture, or direct
examination of various samples such as
sputum, bronchial washings, biopsies,
cerebrospinal fluid, or skin scrapings.
•
Treatment – amphotericin for 10 weeks.
COCCIDIOIDOMYCOSIS
COCCIDIOIDOMYCOSIS
Pathogen: Coccidioides immitis
•
Can be recovered from desert soil, rodent
burrows, archaeological remains, and
mines.
•
Once inhaled in dust, anthrospores
become trapped in the alveolar spaces of
the lungs.
COCCIDIOIDOMYCOSIS
•
Major manifestation - pulmonary
•
Invasion of the CNS may result in
meningitis, headache, nausea, and
emotional disturbance
COCCIDIOIDOMYCOSIS
•
Diagnosis – based on the identification of
spherules in KOH- or GMS- treated
samples collected from patients
•
Amphotericin B – the drug of choice
HISTOPLASMOSIS
HISTOPLASMOSIS
•
Pathogen: Histoplasma capsulatum
•
most common fungal pathogen affecting
humans.
•
Two strains recognized:
a. strain capsulatum - intracellular
parasite, first attacks alveolar
macrophages in lungs
b. strain duboisii - limited to Africa.
HISTOPLASMOSIS
•
Diagnosis – based on the identification of
the distinctive budding yeast in KOH- or
GMS- prepared samples of skin scrapings,
sputum, cerebrospinal fluid, or various
tissues.
Lungs of normal person and a patient with histoplasmosis
HISTOPLASMOSIS
TREATMENT:
•
Amphotericin B - prescribed when
symptoms do not resolve.
•
Ketoconazole – used to treat mild
infections.
PARACOCCIDIOIDOMYCOSIS
PARACOCCIDIOIDOMYCOSIS
•
Pathogen: Paracoccidioides brasiliensis
•
chronic granulomatous disease that
characteristically produces a primary
pulmonary infection, and then
disseminates to form ulcerative
granulomata of the buccal, nasal and
occasionally the gastrointestinal
mucosa.
Paracoccidiomycosis patients –
ulcerative granulomata of
the buccal, nasal mucosa…
PARACOCCIDIOIDOMYCOSIS
•
Diagnosis - KOH or GMS preparations of
tissue samples revealing yeast cells with
multiple buds in a “steering wheel”
formation.
Steering wheel apperance
PARACOCCIDIOIDOMYCOSIS
•
Treatment - Amphotericin B or
Ketoconazole
End of slideshow, click to exit.
Aww… sorry, wrong number..
Systemic Mycoses
caused by OPPORTUNISTIC FUNGI
Systemic Mycoses Caused by
Opportunistic Fungi
• Opportunistic mycoses do not typically
affect health humans.
• One of the more significant causes of
human disease and death and appear
only when their hosts are weakened.
• considered “classical” opportunists
because they are routinely encountered.
• 5 genera of opportunistic fungi
that cause systemic mycoses:
– Aspergillus
– Candida
– Cryptococcus
– Pneumocystis
– and Mucor
ASPERGILLOSIS
ASPERGILLOSIS
•
Pathogens: Aspergillus fumigatus
Aspergillus niger
and Aspergillus flavus
•
a term for several diseases caused by the
inhalation of spores of fungi
•
causes allergies and a growing problem
for AIDS patients.
This an asparagus..
Not an Aspergillus!
ASPERGILLOSIS
•
3 clinical manifestations:
-Hypertensitivity aspergillosismanifests as asthma
-Noninvasive aspergillomas- balllike masses of fungal hyphae
ASPERGILLOSIS
- Acute invasive pulmonary aspergillosismore serious. Signs and symptoms,
which include fever, cough, and pain,
may present as mild pneumonia.
Aspergillus growing inside
the lungs of a bird
ASPERGILLOSIS
•
TREATMENT of hypersensitivity - either the
use of various allergy medications or
desensitization to the allergen.
•
Invasive disease – treated by surgical
removal of aspergillomas and surrounding
tissue, plus high-dose, intravenous
administration of amphotericin B.
CANDIDIASIS
CANDIDIASIS
•
Pathogen: Candida albicans.
•
Common members of the microbiota of
the skin and mucous membranes .
CANDIDIASIS
•
Diagnosis – KOH and GMS
preparations of skin samples, nail
scrapings, cerebrospinal fluid, serum,
urine, sputum, or tissue biopsies can
reveal clusters of budding yeast and
branching pseudohyphae.
CANDIDIASIS

TREATMENT – Nystatin for oral candidiasis
in infants.

Amphotericin B-treatment for invasive
candidiasis.
C R Y P T O C O C C OS I S
CRYPTOCOCCOSIS
•
Pathogen: Cryptococcus neoformans
•
Human infections result from the
inhalation of spores and/or dried yeast
forms made airborne.
•
Cryptococcal meningitis – most
common clinical form of cryptococcal
infection, follows dissemination of the
fungus to the CNS.
CRYPTOCOCCOSIS
•
Diagnosis – involves collecting specimen
samples that correlate with the
symptoms.
CRYPTOCOCCOSIS
•
Treatment – Amphotericin B and 5fluorocytosine administered together for
6-10 weeks.
PNEUMOCYSTIS
PNEUMONIA
PNEUMOCYSTIS PNEUMONIA
•
Pathogen: Pneumocystis jiroveci
•
Originally considered a protozoan but has
been reclassified as a fungus.
•
An obligate parasite and cannot survive
on its own.
PNEUMOCYSTIS PNEUMONIA

Transmission occurs through inhalation of
droplet nuclei containing fungus.

DIAGNOSIS – relies on clinical and
microscopic findings. Chest X-rays usually
reveal abnormal lung features.

Treatment- antiprotozoan drugs
trimethoprim and sulfanilamide.
ZYGOMYCOSES
ZYGOMYCOSES
•
are opportunistic fungal infections caused
by various genera of fungi, Mucor, Rhizopus,
and Absisia.
•
Commonly seen in patients with uncontrolled
diabetes, people who inject illegal drugs, in
some cancer patients, and in some patients
receiving antimicrobial agents.
•
Infections generally develop in the face and
head are.
ZYGOMYCOSES

Conditions which resulted from the
dissemination of the infections
throughout the body in severely
immunocompromised individuals:
a. Rhinocerebral zygomycosis
b. Pulmonary zygomycosis
c. Gastrointestinal zygomycosis
d. Cutaneous zygomycosis
Rhinocerebral zygomycosis
ZYGOMYCOSES
•
DIAGNOSIS – clinically based on patient
history and microscopic findings in fungus.
•
TREATMENT- physical removal of infected
tissues and management of predisposing
factors.
•
Drug of choice- Amphotericin B
administered intravenously for 8-10 weeks.
End of slideshow, click to exit.
Di pa-reportun si KATSUS!
Nyahahahahaha!
Aw.. Cge nlng… .
Superficial, Cutaneous, and
Subcutaneous Mycoses
caused by OPPORTUNISTIC FUNGI
Superficial Mycoses
• Usually acquired by direct contact
with the fungus and are the most
common infections.
• Confined at the outer, dead layers of
the skin, nails, or hair, all of which are
composed of dead cells filled with a
protein called keratin.
Superficial Mycoses

Piedra- a superficial infection that forms
nodules on hair shafts
- infections are normally associated
with the scalp, but faial and pubic hairs
can also be infected
-transmission is via shared hair
brushes and combs, and several
members of a family are typically
infected at the same time
Superficial Mycoses

Black piedra- caused by Piedra Hortae
- characterized as hard,
black nodules encircling the hair shafts

White piedra- caused by Trichosporon
beigelii
- characterized as soft, gray
to white nodules on the hair shafts
Black piedra
Dermatophytoses

Infections caused by dermatophytes.

Fungal infection of nails and skin.

Infections were previously called ringworms
because they resemble a worm lying below
the surface of the skin.
Dermatophytoses



Result from the fungi that use keratin
as a nutrient source and thus
colonize only dead layers of the skin,
nails, and hair.
No living tissues are infected.
Caused by various Epidermophyton,
Microsporum, Trichophyton species.
Types of Diseases Caused by
Dermatophytes
Tinea infections (ringworm)
 - Athlete’s foot (Tinea Pedis)
 -jock itch (Tinea cruris)
 -yeast infections of the mouth and
vagina
often caused by Candida species.

Tinea corporis
Treatment



-can be treated effectively with topical
antifungal agents
-Terbinafine
-griseofulvin
MALASSEZIA
MALASSEZIA INFECTIONS
• -Malassezia furfur is a fungus that infects the
skin. Clinical manifestations include pityriasis,
in which fungal growth disrupts melanin
production to produce discolored patches, and
the most common manifestation of M. furfur
infection- dandruff.
MALASSEZIA INFECTIONS
• Folliculitis- caused by M. furfur
- involves infection of the hair
follicles on the back, chest, and upper
arm, producing follicular papules or
pustules
MALASSEZIA INFECTIONS
• Diagnosis
- examining the patient under ultraviolet
illumination, though some other fungi also
fluoresce.
• Treatment
- solutions of antifungal imidazoles, such
as ketoconazole shampoos.
- topical applications of zinc pyrithione
-selenium sulfide lotions
- propylene glycol
Cutaneous and Subcutaneous
Mycoses
Cutaneous and Subcutaneous
Mycoses
• Infection requires traumatic
introduction of fungal elements
beneath the outer, dead layers of skin.
CHROMOBLASTOMYCOSIS AND
PHAEOHYPHOMYCOSIS

Chromoblastomycosis- small, itchy but painless,
scaly lesions on the skin surface resulting from fungal
growth in subcutaneous tissues near the site of
inoculation.
PHAEOHYPHOMYCOSIS
Paranasal sinus phaeophomycosis –
involves colonization of the nasal
passages and sinuses; it occurs in allergy
sufferers and AIDS patients
 Cerebral phaeophomycosis – caused by
Cladophiolophora bantiana
- has a preference for neural cells and
actively invades the brain
Patients with
chromoblastomycosis
Treatment

Phaeohyphomycosis can be treated with
intraconazole, but the disease is
permanently destructive to tissues

Chromoblastomycosis requires surgical
removal of infected and surrounding
tissues followed by antifungal therapy.
MYCETOMAS
MYCETOMAS

- tumorlike infections of the skin, fascia
(lining of muscles), and bones of the
hands of feet caused by mycelial fungi


This fungi live in soil and are introduced
into humans via the prick wounds and
scrapes caused by twigs, thorns, or
leaves contaminated with fungi.
Treatment


Surgical removal of the mycetoma
Anti fungal therapy with ketoconazole
SPOROTRICHOSIS
SPOROTRICHOSIS

Pathogen: Sporothrix schenckii

Also called “rose-gardener’s disease”, a
subcutaneous infection limited to the
arms and legs.
Treatment




Topical applications of saturated
potassium iodide for several months
Itraconazole
Terbinafine
It can be prevented by wearing of
gloves, long clothing and shoes to
prevent inoculation.
Summing it all up…
CATEGORIES OF FUNGAL AGENTS
True Fungal Pathogens
Systemic Mycoses
Opportunistic Fungi
Systemic
Mycoses
Blastomyces
Aspergillus
Coccidioides
Candida
Histoplasma
Paracoccidioides
Cryptococcus
Pneumocystis
Mucor
Superficial
Mycoses
Dermatophytes
Malassezia
Cutaneous and
Subcutaneous
Chromoblastomycosis
Phaehyphomycosis
mycelial fungi
Sporothrix
Going back...
Clinical Manifestations
of Mycoses
• Fungal infections (most common)
• Toxicoses (poisoning)
• Allergies (hypersensitivity reactions)
TOXICOSIS
Toxicosis
• Mycotoxicosis – caused by eating
food contaminated with fungal
toxins only
• Mycetismus - poisoning caused by
eating the fungus
Mycotoxicosis
• Mycotoxins – chemicals produced
by fungi during metabolism, that are
poisonous to humans
• Aflatoxins – are the most well-known
mycotoxins, produced by certain
species of Aspergillus
Mycetismus
• Amanita phalloides
– “death cap mushroom”
– Produces the deadliest mushroom toxin
Allergies to Fungi
• Allergens – spores or other fungal
elements that cause type I
hypersensitivities, or more rarely,
type III