This document discusses various fungal infections that can affect the oral cavity and respiratory tract, including candidiasis, aspergillosis, and zygomycosis. It describes the characteristics and morphology of fungi, including molds, yeasts, dimorphic fungi. It then covers the pathogenesis, clinical manifestations, diagnosis and treatment of the main opportunistic fungal infections.

1. Fungal infections of the oral
cavity
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2. Medical Mycology
• Fungi were discovered before bacteria & viruses
• Most fungi cause skin or cosmetic infections
while bacteria & viruses cause fatal diseases
• Clinical Mycology has entered “Golden Age” in
modern medicine due to:
•Organ transplantation
•Immunosuppressive drugs
•Anticancer drugs
•Broad-spectrum antimicrobials
•HIV-disease
Immunosuppression
Opportunistic Fungal Infections
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3. Fungi : General Characteristics
• Are eukaryotic (possess a true nucleus with nuclear
membrane & mitochondria)
Cell membrane
• Have ergosterol which is specific target for antifungal
agents (cholestrol in mammalian cells)
Cell Wall
Lacks
• Peptidoglycan
• Techoic acids
• Lipopolysaccharide
Contains
• Peptidomannan
• Glycan (target for
new antifungal agents)
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4. Fungi Groups
On the basis of Morphology
1. Molds (filamentous fungi)
• Most fungi are composed of filamentous
(tubular) structures called hyphae. May be
septated OR Aseptated
Aseptate hyphae
Septate hyphae
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5. Types of Hyphae
• Vegetative hyphae: penetrate the media and absorb food
• Aerial hyphae : are directed above the surface of media
• Reproductive hyphae : Aerial hyphae that carry different
spores
• Mycelium : A collection of hyphae
Reproductive
Hyphae & conidia
Mycelium
(thallus)
Surface of
media
Aerial
hyphae
Vegetative
hyphae
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6. Fungi Groups
On the basis of morphology
2. Yeasts
• Unicellular (rounded or oval)
• Reproduce by budding
• The only example of pathogenic
yeast is Crptococcus
neoformans
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7. Fungi Groups
On the basis of morphology
3. Yeast-Like
• Unicellular (rounded or oval)
• Reproduce by budding but buds fail to
detach and may form short chains of cells
called pseudohyphae
• Pseudohyphae are produced during
infection and have diagnostic value
• Example: Candida
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8. Fungi Groups
On the basis of Morphology
4. Dimorphic Fungi
• Able to grow in two different forms
• As molds at room temperature
• As yeasts on incubation at 370C &
during infection in body
“Mold in the cold, yeast in the heat”
• Example: Histoplasma capsulatum
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9. Opportunistic Infections of the URT&
LRT
• Candidiasis
• Cryptococcosis
• Aspergillosis
• Zygomycosis
***ANY fungus found in nature may
give rise to opportunistic mycoses ***
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10. CANDIDIASIS
• Most commonly encountered opportunistic
mycoses worldwide
• Cellular immunity protects against
mucocutaneous candidiasis, neutrophiles protect
against invasive candidiasis
• Endogenous infection.
• Etiology: Candida spp. Most common:
 C. albicans
 C. tropicalis
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11. Candida
Morphologicfal Features
• Micr. Budding yeast cells
Pseudohyphae, true hyphae
• Macr. Creamy yeast colonies (SDA)
• Germ tube
• Chlamydospore
• Identification
 Germ tube
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12. Sabouraud Dextrose agar
Candida albicans
Candida albicans
Microscopic Morphology
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13. Candida
Pathogenicity
• Attachment (Germ tube is more
adhesive than yeast cell)
• Adherence to plastic surfaces (catheter,
prosthetic valve..)
• Protease
• Phospholipase
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14. CANDIDIASIS
Risk factors
• Physiological. Pregnancy, elderly, infancy
• Traumatic. Burn, infection
• Hematological. Cellular immune deficiency,
AIDS, chronic granulamatous disease,
aplastic anemia, leukemia, lymphoma...
• Endocrinological. DM
• Iatrogenic. Oral contraceptives, antibiotics,
steroid, chemotherapy, catheter...
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15. Candidiasis
Clinical manifestations
1. CUTANEOUS and SUBCUTANEOUS
•
a)
b)
c)
Oral
Pseudomembernous (thrush)
Erythematous
Hyperplastic
• Vaginal
• Dermatitis
• Diaper rash
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16. Candida albicans
Granulomatous lesions involving
Candida diaper rash
the hands.
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17. Candida albicana
The white material are masses of the yeast
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18. CANDIDIASIS
Clinical manifestations
2.SYSTEMIC
• Esophagitis
• Pulmonary inf.
• UTI( Cystitis)
• Osteomyelitis
• CNS (Menengitis)
• Skin lesions
• CVS
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19. CANDIDIASIS
Diagnosis
• Direct micr.ic examination
Yeast cells, pseudohyphae, true hyphae
• Culture
SDA, routine bacteriological media
• Serology
Detection of mannan antigen
(ELISA, RIA, IF, latex agglutination)
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20. CANDIDIASIS
Treatment
• CUTANEOUS
Topical antifungal: Ketoconazole, miconazole,
nystatin
• SYSTEMIC
Amphotericin B
Fluconazole, itraconazole
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21. Aspergillosis
Causative Agent
• Aspergillus fumigatus
Systemic infection
• Aspergillus flavus
• Aspergillus niger- mostly local infection;
otomycosis
• Are molds that have septate hyphae with Vshaped branches (Fruiting body of Aspergillus)
Source of infection
• Widely distributed in environment
• Transmitted by air-borne light spores
• High environmental load is associated with sick
building syndrome & contaminated AC system
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22. Aspergillus
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23. Aspergillosis
Pathogenesis & Clinical features
Aspergillus can colonize and invade:
• Lungs
• Wounds, burns
• Cornea
• External ear
• Paranasal sinuses
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24. Aspergillosis
In lungs can cause:
a) Hypersensitivity Reaction:
Spores colonise RT without invasion and lead to
allergic asthma, rhinitis, bronchopulmonary aspergillosis
b) Aspergilloma (fungus ball):
the spores colonise paranasal sinuses or a pre-existing
cavity in lung (TB cavity)
The radiological appearance may be similar to malignancy.
c) Invasive Aspergillosis
In immunocompromised can invade lungs causing hemoptysis
& granuloma and disseminate to other organs
Fatality rate 100% if not diagnosed and treated promptly.
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25. Aspergillosis
Lab Diagnosis
Specimens : sputum, BM aspirate, biopsy
Direct Microscopy
• Shows branching septate hyphae
Cultures : Microscopy shows radiating chains of spores
Serology
• In allergic condition: high levels of specific IgE
• Galactomannan in invasive aspergillosis
Treatment
• Invasive aspergillosis
Amphotericin B
• Allergic conditions
Steroids & antifungals
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26. Zygomycosis
Mucormycosis
• Causative agents; saprophtic molds
• Rhizopus, Mucor & Absidia
• Have broad, hyaline aseptate hyphae
• Have large no. of asexual spores inside a sporangium
• Risk factors
Diabetic ketoacidosis,
immunosuppression
• Pathogenesis Inhalation of sporangiospores
• Infected tissue vascular invasion,
thrombus, infarct,
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27. ZYGOMYCOSIS
Clinical manifestations
I. RHINOCEREBRAL
• Nose, paranasal sinuses, eye, brain and meninges are
involved
• Orbital cellulitis
II. THORACIC
• Pulmonary lesions, parenchymal necrosis
III. LOCAL
• Posttraumatic kidney infection.
• Skin inf. following burn or surgery
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28. Zygomycosis
Mucormycosis
Diseases
• Rhinocerebral zygomycosis
o Extensive cellulitis of nasal mucosa, paranasal
sinuses, orbit & brain
o Rapidly fatal
• Pulmonary & disseminated infections
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29. Zygomycosis in a diabetic patient
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30. Disease(s): Rhinocerebral zygomycosis
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31. ZYGOMYCOSIS
Diagnosis
• Samples Sputum, BAL, biopsy of
paranasal sinuses..
• Direct exam. Nonseptate, ribbon-like
hyphae which branch at right angles,
sporangium
• Culture SDA (cotton candy appearance)
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32. Image: Sporangia showing different stages of sporangiospore
development in the large sporangium, human nasal polyp,
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33. Treatment
• Surgical debridement
• Amphotericin B
***High mortality rate
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34. Case study
• A young Diabetic girl develops acute fatigue and
fever. Her pediatrician discovers a leukemia and
the girl is promptly treated with broad acting anticancer therapy. Two weeks after the therapy she
started to developed a severe pneumonia which
does not respond to antimicrobial antibiotics. A
biopsy from the lung was taken and plated on
Sabouraud dextrose agar containing
antibacterial antibiotics. After incubation at 250C,
a mold is seen. On further examination the girl is
treated with amphotericin B and recover. The
disease she had was
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35. Questions
• What is the identity of the isolate ?
• In what patient population does this
organism normally cause infection?
• How can you investigate the patient?
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