Opportunistic Fungi

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. • 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
Causative agents

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

6. Fungal spores enters through respiratory
tract

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 surroundedby
dense fibrous wall
presents with cough,
sputum production
• Haemoptysis occurs
due to invasion of

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

12. Superficial Infections
1. Sinusitis
2. Mycotic keratitis
3. Otomycosis

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

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

23. Laboratory diagnosis
Specimens
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

24. Broad, aspetate hyphae in tissue sections

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

26. Mucor

28. Treatment
Intravenous amphotericin B combined, where appropriate
with surgical drainage

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

32. www.freelivedoctor.com

33. Dimorphic chaterization of Pencillium
Marneffei

34. Mycelial growth of P
. marneffei Microscopic examination

35. Treatment
Penicillosis can be treated with amphotericin B and followed
by oral itraconazole