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Fungal infections of the oral cavity

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Clinical Microbiology
Fifth Year

Publié dans : Santé & Médecine, Technologie
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Fungal infections of the oral cavity

  1. 1. Fungal infections of the oral cavity 1
  2. 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 2
  3. 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) 3
  4. 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 4
  5. 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 5
  6. 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 6
  7. 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 7
  8. 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 8
  9. 9. Opportunistic Infections of the URT& LRT • Candidiasis • Cryptococcosis • Aspergillosis • Zygomycosis ***ANY fungus found in nature may give rise to opportunistic mycoses *** 9
  10. 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 10
  11. 11. Candida Morphologicfal Features • Micr. Budding yeast cells Pseudohyphae, true hyphae • Macr. Creamy yeast colonies (SDA) • Germ tube • Chlamydospore • Identification  Germ tube 11
  12. 12. Sabouraud Dextrose agar Candida albicans Candida albicans Microscopic Morphology 12
  13. 13. Candida Pathogenicity • Attachment (Germ tube is more adhesive than yeast cell) • Adherence to plastic surfaces (catheter, prosthetic valve..) • Protease • Phospholipase 13
  14. 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... 14
  15. 15. Candidiasis Clinical manifestations 1. CUTANEOUS and SUBCUTANEOUS • a) b) c) Oral Pseudomembernous (thrush) Erythematous Hyperplastic • Vaginal • Dermatitis • Diaper rash 15
  16. 16. Candida albicans Granulomatous lesions involving Candida diaper rash the hands. 16
  17. 17. Candida albicana The white material are masses of the yeast 17
  18. 18. CANDIDIASIS Clinical manifestations 2.SYSTEMIC • Esophagitis • Pulmonary inf. • UTI( Cystitis) • Osteomyelitis • CNS (Menengitis) • Skin lesions • CVS 18
  19. 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) 19
  20. 20. CANDIDIASIS Treatment • CUTANEOUS Topical antifungal: Ketoconazole, miconazole, nystatin • SYSTEMIC Amphotericin B Fluconazole, itraconazole 20
  21. 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 21
  22. 22. Aspergillus 22
  23. 23. Aspergillosis Pathogenesis & Clinical features Aspergillus can colonize and invade: • Lungs • Wounds, burns • Cornea • External ear • Paranasal sinuses 23
  24. 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. 24
  25. 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 25
  26. 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, 26
  27. 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 27
  28. 28. Zygomycosis Mucormycosis Diseases • Rhinocerebral zygomycosis o Extensive cellulitis of nasal mucosa, paranasal sinuses, orbit & brain o Rapidly fatal • Pulmonary & disseminated infections 28
  29. 29. Zygomycosis in a diabetic patient 29
  30. 30. Disease(s): Rhinocerebral zygomycosis 30
  31. 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) 31
  32. 32. Image: Sporangia showing different stages of sporangiospore development in the large sporangium, human nasal polyp, 32
  33. 33. Treatment • Surgical debridement • Amphotericin B ***High mortality rate 33
  34. 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 34
  35. 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? 35