2. Opportunistic mycoses
Occurrs in human’s with a compromised immune system
Causative agents are normal resident flora that become
pathogenic only when the host's immune defenses are
altered, as in immunosuppressive therapy, in a chronic
disease, such as diabetes mellitus, or during steroid or
antibacterial therapy that upsets the balance of bacterial
flora in the body
3. Causative agents
• Candida species
• Cryptococcus neoformans
• Aspergillus species
• Zygomycosis (Rhizopus, mucor, absidia)
• Penicillium species
• Fusarium species
• Alternaria species
***ANY fungus found in nature may give rise to
opportunistic mycoses ***
4. Aspergillosis
• Aspergillus species are ubiquitous saprophytes in
nature
• In nature >300 species of Aspergillus exist, few are
important as human pathogens
•
•
•
•
•
1 A.fumigatus
2 A.niger
3 A.flavus
4 A.terreus
5 A.nidulans
5. Pathogenesis
This mold produces abundant small conidia that are easily
aerosolized
Following inhalation of these conidia, atopic individuals often
develop severe allergic reactions to the conidial antigens
In immunocompromised patients, the conidia may germinate
to produce hyphae that invade the lungs and other tissues
7. The Aspergillus species can cause a variety of clinical
syndromes
1. Pulmonary aspergillosis
a) Allergic asthma
b) Bronchopulmonary aspergillosis
c) Aspergilloma
2. Invasive aspergillosis
3. Superficial infections
8. Allergic asthma
In some atopic individuals, development of IgE antibodies to
the surface antigens of Aspergillus conidia elicits an
immediate asthmatic reaction upon subsequent exposure
Bronchopulmonary aspergillosis
The conidia germinate and hyphae colonize the bronchial
tree without invading the lung parenchyma
The condition is made worse by the development of
hypersensitivity to the fungus
9. Aspergilloma
• Fungus colonize preexisting
(Tuberculosis ) cavities in
the lung and form compact
ball of mycelium which is
later surrounded by dense
fibrous wall presents with
cough, sputum production
• Haemoptysis occurs due to
invasion of blood vessels
• Cases of aspergilloma rarely
become invasive
10.
11. Invasive aspergillosis
In invasive aspergillosis, the fungus first causes pneumonia,
actively invades the lung tissue and disseminates to involve
other organs, for example, the brain, kidneys or heart
This form occurs in severly immuno compromised individuals
who have a serious underlying illness
Neutropenia is the most common predisposing factor and
A. fumigatus is the species most frequently involved
13. Laboratory diagnosis
Specimens
Sputum, other respiratory specimens, lung biopsy specimens
Microscopic examination
KOH mount
The fungus appears as non-pigmented septate mycelium,
3-5 µm in diameter with chatracteristic dichotomous
branching and an irregular outline
Rarely the characteristic sporing heads of Aspergillus species
are present
14. Culture
Aspergillus species grow readily on SDA without
cycloheximide at 25-370C
Colonies appear after 1-2 days of incubation
Species are identified according to the morphology of their
conidial structures
Skin tests
Skin tests with Aspergillus species antigen are useful for
the diagnosis of allergic broncho pulmonary aspergillosis
15.
16. Treatment
Invasive aspergillosis is treated with intravenous
amphotericin B
In recent years, intravenous formulations of azoles, such as
voriconazole, are being evaluated
17. Zygomycosis
Also called as Mucormycosis, Phycomycosis
It is an invasive disease caused by zygomycetes, principally
by the species of Rhizopus, Mucor, Rhizomucor, Absidia
These fungi are ubiquitous theromtolerant saprophyte;
spores are present in air and dust
The conditions that place patients at risk include acidosis,
leukemias, lymphoma, corticosteroid treatment, severe
burns, immunodeficiencies
18. Clinical manifestations
There are a number of different clinical varieties of
mucormycosis
1. Rhinocerebral Mucormycosis
2. Thoracic Mucormycosis
3. Other sites of invasion
19. Rhinocerebral Mucormycosis
Results from germination of the sporangiospores in the
nasal passages and invasion of the hyphae into the blood
vessels, causing thrombosis, infarction and necrosis
The disease can progress rapidly with invasion of the sinuses,
eyes, cranial bones and brain
Blood vessels and nerves are damaged, and patients develop
edema of the involved facial area, a bloody nasal exudate,
and orbital cellulitis
It is almost invariably associated with acute diabetes mellitus
or with debilitating diseases such as leukemia or lymphoma
20. Thoracic Mucormycosis
This follows inhalation of the sporangiospores with invasion
of the lung parenchyma and vasculature
In both locations, ischemic necrosis causes massive tissue
destruction
Other sites of invasion
Primary cutaneous infections such as skin infections
following burns or surgery have also been reported
Subcutaneous zygomycosis cases are also reported
21.
22.
23. Laboratory diagnosis
Secimens
Nasal discharge, sputum and biopsy specimens
Microscopy
KOH mount, may reveal the characteristic broad, aseptate,
branched mycelium and sometimes distorted hyphae
They are seen much more clearly when stained with
methenamine-silver stain
The hyphae of these fungi do not stain with PAS
25. Culture
The fungi are readily isolated on SDA with antibiotics
without cycloheximide, producing abundant cottony
colonies
Identification of the species is based on the sporangial
structures
29. Penicillosis
There are more than 150 species; most important species
Penicillium marneffei
Penicillium marneffei –thermally dimorphic fungi
Penicillium species are saprophytes; present in the
environment and grow on various substrates such as bread,
jam, fruit and cheese
30. Pathogenesis and clinical features
P. marneffei has been reported to be an important
opportunistic pathogen in the HIV infected
It causes disseminated infection with multiple organ
involvement
31. Laboratory diagnosis
The yeast are small, oval, 2-4 µm in diameter
The mycelia form produces red diffusible pigment and
morphologically resembles other members of the
Penicillium species
Penicillum species possess septate hyphae with branched
conidiophores, with two rows of sterigmata bearing chains
of rows; the appearance is like a brush or broom