1. Dental / Optometry Fundamentals II Stephen A. Moser, Ph.D. 10/26/2011
Mycology
Dental / Optometry Fundamentals II
Stephen A. Moser, Ph.D.
10/26/2011

2. Epidemiology Geography Transmission of infection Endemic mycoses
Worldwide mycoses
Transmission of infection
Respiratory inhalation (systemic mycoses)
Cutaneous inoculation (sporotrichosis)
Systemic invasion by opportunistic normal flora (candidiasis)
Contact with infected hosts (dermatophytoses)

3. Epidemiology (Cont.) Risk factors and manifestations of disease
True pathogens versus opportunists
Environmental risk factors for systemic fungal disease
Location and travel
Occupation
Host defenses and susceptibility to systemic fungal disease (CMI most important)
Congenital and acquired T cell deficiencies (including AIDS)
Immunosuppression (transplants and malignancies)
Diabetes mellitus

4. Endemic Distribution for Blastomycosis

5. General Characteristics
Aerobic - obligate or facultative
Eukaryotic: membrane bound nucleus and cytoplasmic organelles (may be multinucleate)
Achlorophyllous
Morphology (unicellular or multicellular)
Saprophytic (heterotrophic)

6. Characteristics of Fungal Cells
Cell wall: multilayered polysaccharide
Cellulose, glucans, mannans, chitin, polypeptides
Absence of teichoic acids, peptidoglycan, LPS
Cell membrane
Phospholipid bilayer
Ergosterol (relate to chemotherapy)
Cytoplasm - typical eukaryotic organelles
Nucleus - either uninucleate or multinucleate

7. Characteristics of Fungal Cells
Capsule
Present in some species (e.G. Cryptococcus neoformans)
Amorphous polysaccharide coating
Functions and activities
Antiphagocytic
Antigenic

8. Characteristics of Fungal Cells
Growth forms
Yeast - unicellular fungi which reproduce by budding (Cryptococcus)
Mold - hyphae (mycelium)
Septate hyphae (Aspergillus)
Non-septate, coenocytic hyphae (Mucor)
Pseudohyphae (Candida albicans)
Thermal dimorphism

9. Differences Between Bacteria and Fungi

10. Examples of Yeast & Pseudohyphae
Blastoconidia
Pseudohypha

11. Blastomyces dermatitidis Thermal Dimorphism

12. Example of True Septate Hyphae

13. Non-septate Hyphae

14. Asexual Reproduction Conidia (spores) – asexual structures
Blastospores – formed by budding yeasts (Blastomyces)
Chlamydospores – terminal or intercalary cells with thick walls (Candida albicans)
Arthrospores – formed by fragmentation of hyphae (Coccidioides immitis)
Sproangiospores – formed in sporangia by cleavage (Rhizopus)

15. Classification Based on Sexual Phase
Ascomycetes: Aspergillus, Histoplasma, Blastomyces, Dermatophytes
Basidiomycetes: Cryptococcus, Mushrooms
Zygomycetes: Order Mucorales - Mucor, Rhizopus
Deuteromycetes (Fungi Imperfecti): Sporothrix, Coccidioides, Candida

16. Clinical Types of Fungal Infections

17. Routes of Infection Inhalation of spores – major factor
Inoculation of spores into skin
Disease by normal flora in compromised host (Candida)
Hypersensitivity
Contact with infected host (Dermatophytes)
Mycotoxins

18. Laboratory Diagnosis of Fungal Infections
Microscopic Examination of tissues and body fluids
Gram stain
Giemsa
India Ink
Potassium hydroxide (KOH) wet prep
Hematoxylin and Eosin stain
Periodic-Acid Schiff stain (PAS)
Gomori-Methenamine Silver stain (GMS)
Mucicarmine or Alcian Blue stain

19. Budding Yeast - Gram Stain
Staphylococcus
Candida

20. Encapsulated Yeast - India Ink

21. KOH Prep - Broad-base Budding Yeast

22. H&E Stain - Budding Yeasts

23. GMS Stain - Septate Hyphae

24. Mucicarmine Stain - C. neoformans

25. Histopathological Response to Fungal Infection
Acute pyogenic abscess (Candida)
Chronic granuloma formation (Histoplasma)
Chronic, localized dermal inflammation (Dermatophytes)
Mixed pyogenic and granulomatous inflammation (Blastomyces)
Blood vessel invasion with thrombosis and infarction (Mucor, Aspergillus)
Hypersensitivity without tissue reaction (allergic bronchopulmonary aspergillosis)

26. Fungal Cultures Utilize Sabouraud agar with antibiotics
Identification criteria
Temperature of growth
Rate of growth
Colonial and microscopic morphology
Sporulation pattern
Biochemical reactions (yeast)

27. Fungal Serology
Generally poor and not as useful as in other pathogens such as viruses and bacteria, with some exceptions.
Cryptococcal antigen by latex agglutination: serum and CSF.
Coccidioides - early IgM response is useful for identification of acute primary disease - CSF IgG prognostic value.
Skin tests for DTH - problems:
Cross-reactivity.
High positive rate in endemic areas.

28. Candidiasis Clinical manifestations Mucosal Cutaneous
Vaginitis
Esophagitis
Oral thrush
Cutaneous
Chronic mucocutaneous
Systemic
Fungemia
Hepato-spleenic
Endophthalmitis
Renal
Urinary tract

29. Oral Candidiasis

30. Wet Mount - Candidiasis

31. Mucocutaneous Candidiasis

32. Candida sp. Tissue GMS Stain

33. Aspergillosis Clinical manifestations Pneumonia Aspergilloma
Allergic bronchopulmonary
Disseminated multiorgan involvement

34. Aspergilloma

35. Allergic Bronchopulmonary Aspergillosis

36. CNS Aspergillosis

37. Aspergillus sp – GMS Stain

38. Zygomycosis Clinical manifestations Sinusitis Rhinocerebral Pulmonary
Renal

39. Rhinocerebral Mucormycosis in Diabetic Ketoacidosis

40. Postmortem – Rhinocerebral Mucormycosis

41. Non-septate Branching Hyphae (PAS)

42. Histoplasmosis Clinical manifestations
Most cases mild or sub-clinical pulmonary disease
Dissemination appears to be common
Pneumonia
Chronic progressive pulmonary (cavitary)
Histoplasmoma
Disseminated

43. Histoplasmosis – Calcified Lesions

44. Histoplasmosis- GMS

45. Histoplasmosis – Bone Marrow
H. capsulatum
Histiocyte

46. Histoplasma capsulatum
In vitro
In vivo

47. Presumed Ocular Histoplasmosis
Thought to be a late stage of primary histoplasmosis.
Causes abnormal blood vessels – scar tissue.
Organism has not been found in eye.
Treated with laser surgery.

48. Risk Factors for Endogenous Endophthalmitis
Candidia species
Central venous lines, neutropenia, abdominal surgery, intravenous drug abuse, broad-spectrum antibiotics
Aspergillus species
Neutropenia, endocarditis, intravenous drug abuse, pulmonary disease being treated with high dose steroids, organ and stem cell transplant.
H. capsulatum
C. immitis
B. dermatitidis
C. neoformans
May accompany disseminated disease
Fusarium species
Neutopenia, intravenous drug abuse

49. Fungal Keratitis

50. Chemotherapy FDA approved Investigational
Polyenes (Amphotericin B, lipid encapsulated forms)
Azoles (fluconazole, itraconazole, ketoconazole, voriconazole)
Echinocandin (Caspofungin, Micafungin, Anidulafungin)
Nucleoside derivatives (5-flurocytosine)
Allyamines (Terbinafine)
Microtubule disruption (Griseofulvin)
Investigational
Nikkomycins (chitin synthase inhibitors)
Echinocandin/pnemocandin/lipopeptide class (inhibit glycan synthesis)

51. Antifungal Drugs for Systemic Mycoses - Amphotericin B
Mode of Action
Binds to ergosterol, increases membrane permeability resulting in leakage of cytoplasmic components and cell death – Fungicidal
Spectrum of Activity
Candida, Crypto, Aspergillus, Histo, Blasto, Cocci, etc
Limitations
Nephrotoxicity

52. Antifungal Drugs for Systemic Mycoses - Fluconazole
Mode of Action
Prevents ergosterol synthesis by inhibiting the C-14 demethylation step (cytochrome P-450 rx)
Fungistatic
Spectrum of Activity
Candida, Crypto, Trichsporonosis, dermatophytes
Limitations
Resistance in some Candida sp – krusei and glabrata
Not effective for non-dermatophyte moulds.

53. Antifungal Drugs for Systemic Mycoses -Echinocandins
Mode of Action
Prevents synthesis of beta 1,3-glucan required for cell wall.
Fungistatic
Spectrum of activity
Aspergillus, Candida
NOT effective against Cryptococcus, zygomycetes.

54. Early Diagnosis of Invasive Fungal Infections
Obstacles
Because of Immunosuppression typical signs and symptoms of infection are frequently absent
Few clinical features are uniquely specific for systemic fungal infection
Sputum and blood cultures are frequently negative
Invasive procedures
May be necessary for definitive diagnosis
Are often complicated in severely immunocompromised patient

55. Early Diagnosis of Invasive Fungal Infections (Continued)
Benefits
Early diagnosis permits selection of a therapy of maximal effectiveness
Early intervention with antifungal therapy may help decrease the high mortality rate associated with serious systemic mycoses

56. Major Areas Covered How fungi differ from bacteria
The major fungal infections
The epidemiology of fungal infections
Pathology of fungal infections
Mechanism of action of antifungal agents