1. بسم الله الرحمن الرحيم 1 1 1

2. Head of Microbiology Department
Mycology
Dr. Manal El Said
Head of Microbiology Department

3. Basic Mycology Structure & Growth
Fungi are eukaryotic organisms that exist in two basic forms: yeasts & molds.
Yeasts are single cells & reproduce by budding (daughter cells are unequal in size)
Molds consist of long filaments of cells called hyphae & reproduce by cell division (daughter cells are equal in size).

4. Basic Mycology
Structure & Growth

5. Basic Mycology Structure & Growth
Some fungi are dimorphic, i.e., they can exist either as yeasts or molds, depending on temperature.
- Room temperature (25°C)
molds
- Body temperature (37°C)
yeasts

6. Basic Mycology Structure & Growth Fungal cell wall is made of chitin
Fungal cell membrane contains ergosterol.

7. Basic Mycology Pathogenesis
Infection with certain systemic fungi, such as Histoplasma & Coccidioides, granulomatous host defense response (composed of macrophages & helper T cells) & can be detected by skin tests.
Infection with Aspergillus, Mucor & Sporothrix
pyogenic response (composed of neutrophils).

8. Basic Mycology Fungal Toxins & Allergies
Ingestion of Amanita mushrooms liver necrosis due to presence of two fungal toxins, amanitin & phalloidin.Amanitin inhibits RNA polymerase (synthesizes cellular mRNA).

9. Basic Mycology Fungal Toxins & Allergies
Ingestion of peanuts & grains contaminated with Aspergillus flavus liver cancer due to presence of aflatoxin.
Aflatoxin epoxide mutation in p53 gene loss of p53 tumor suppressor protein.

10. Basic Mycology Fungal Toxins & Allergies
Inhalation of spores of Aspergillus fumigatus can cause allergic bronchopulmonary aspergillosis.
This is IgE-mediated immediate hypersensitivity response.

11. Basic Mycology Laboratory Diagnosis
Microscopic examination of KOH preparation can reveal presence of fungal structures.
KOH dissolve human cells, allowing visualization of fungi.

12. Basic Mycology Laboratory Diagnosis
Sabouraud's agar is used to grow fungi because its low pH inhibits growth of bacteria, allowing slower-growing fungi to emerge.

13. Basic Mycology Laboratory Diagnosis
DNA probes can be used to identify fungi growing in culture at much earlier stage, i.e., when colony size is much smaller.

14. Basic Mycology Laboratory Diagnosis
Tests for presence of fungal antigens & for presence of antibodies to fungal antigens are often used.
Two commonly used tests in patient's serum are:
- Cryptococcal antigen in spinal fluid
- Coccidioides antibodies.

15. Basic Mycology Antifungal Therapy
Amphotericin B binds to fungal cell membranes at site of ergosterol disrupts integrity of membranes
Azole drugs, such as itraconazole, fluconazole, & ketoconazole inhibit synthesis of ergosterol.
Echinocandins inhibit synthesis of D-glucan, which (component of fungal cell wall).

16. Fungi Causing Cutaneous & Subcutaneous Mycoses

17. Trichophyton, Microsporum, Epidermophyton Species
Dermatophytes
Trichophyton, Microsporum, Epidermophyton Species
Cutaneous (Superficial) mycoses are confined to outer layers of skin, hair, & nails & do not invade living tissues.
The fungi are called dermatophytes.
Dermatophytes (keratinophilic fungi) , produce extracellular enzymes (keratinases)
hydrolyzing keratin.

18. Trichophyton, Microsporum, Epidermophyton Species
Dermatophytes
Trichophyton, Microsporum, Epidermophyton Species
Characteristics
These fungi are molds that use keratin as nutritional source.
Habitat is human skin
Transmission
Direct contact with skin scales.

19. Trichophyton, Microsporum, Epidermophyton Species
Dermatophytes
Trichophyton, Microsporum, Epidermophyton Species
Diseases
Tinea means "ringworm" or "moth-like". Dermatologists use term to refer to variety of lesions of skin or scalp.
Tinea corporis - small lesions occurring anywhere on body
Tinea pedis - "athlete's foot". Infection of toe webs & soles of feet.
Tinea unguium (onychomycosis)- nails. Clipped are used for culture
Tinea capitis - head. Frequently found in children
Tinea cruris - "jock itch". Infection of groin, perineum or perianal area.
Tinea barbae - ringworm of bearded areas of face & neck

20. Dermatophytes Tinea corporis Tinea pedis (athlete's foot)
Trichophyton, Microsporum, Epidermophyton Species
Tinea corporis
Tinea pedis (athlete's foot)
Onychomycosis
"Tinea capitis
Tinea faciei”
Tinea cruris

21. Sporothrix schenckii Disease Sporotrichosis. Characteristics
Thermally dimorphic
Habitat is soil or vegetation.
Transmission
Mold spores enter skin in puncture wounds caused by rose thorns & other sharp objects in the garden.

22. Sporothrix schenckii Pathogenesis
Local abscess or ulcer with nodules in draining lymphatics.

23. Fungi Causing Systemic Mycoses

24. 1-Histoplasma capsulatum
Disease
Histoplasmosis.
Characteristics
Thermally dimorphic
Mold grows in soil enriched with bird droppings
Transmission
Inhalation of airborne asexual spores

25. 1-Histoplasma capsulatum
Laboratory Diagnosis
Skin Test
Histoplasmin (mycelial extract) is the antigen.
Useful for epidemiologic purposes to determine incidence of infection.
Positive result indicates that infection has occurred
It cannot be used to diagnose active disease.
Skin testing can induce antibodies, so serologic tests must be done first.

26. 2-Coccidioides immitis
Disease
Coccidioidomycosis.
Characteristics
Thermally dimorphic.
Natural habitat is the soil
Transmission
Inhalation of airborne arthrospores.

27. 2-Coccidioides immitis
Laboratory Diagnosis
Skin Test
Coccidioidin, (mycelial extract) or spherulin, (extract of spherules) is the antigen.
Determining if the patient has been infected.
Positive test indicates prior infection but not necessarily active disease.

28. 3-Blastomyces dermatitidis
Disease
Blastomycosis.
Characteristics
Thermally dimorphic
Yeast form has single, broad-based bud & thick, refractile wall.
Natural habitat is soil
Transmission
Inhalation of airborne spores (conidia).
Transmission

29. 4-Paracoccidioides brasiliensis
Disease
Paracoccidioidomycosis.
Characteristics
Thermally dimorphic .
Transmission
Inhalation of airborne conidia.
Disease
Characteristics
Transmission

30. Fungi Causing Opportunistic Mycoses

31. Fungi Causing Opportunistic Mycoses
1-Candida albicans
Disease
Thrush,
Disseminated candidiasis
Chronic mucocutaneous candidiasis.
Characteristics
Candida albicans is yeast when part of normal flora of mucous membranes but forms pseudohyphae & hyphae when it invades tissue.
The yeast form produces germ tubes when
incubated in serum at 37°C.

32. Fungi Causing Opportunistic Mycoses
1-Candida albicans
Transmission
Part of the normal flora of skin, mucous membranes & GI tract.
No person-to-person transmission.

33. Fungi Causing Opportunistic Mycoses
1-Candida albicans
Pathogenesis
Predisposing factors include:
- Reduced cell-mediated immunity
Altered skin & mucous membrane
Suppression of normal flora
Presence of foreign bodies.
Thrush is common in:
Infants
immunosuppressed patients
persons receiving antibiotic therapy.

34. Fungi Causing Opportunistic Mycoses
1-Candida albicans
Pathogenesis
Skin lesions occur on moisture-damaged skin.
Disseminated infections, such as endocarditis and endophthalmitis, occur in immunosuppressed patients and intravenous drug users.
Chronic mucocutaneous candidiasis occurs in children with a T-cell defect in immunity to Candida.

35. Fungi Causing Opportunistic Mycoses
1-Candida albicans
Oral thrush. CDC
Candida albicans showing germ tube production in serum.

36. Fungi Causing Opportunistic Mycoses
1-Candida albicans
Laboratory Diagnosis
Microscopic examination of tissue reveals yeasts & pseudohyphae.
The yeast is gram-positive.
Germ tube formation & production of chlamydospores distinguish C. albicans from other species of Candida.
Skin Test to determine competency of cell-mediated immunity .
Out-pouching of cell wall that becomes tubular & does not have constriction at its base

37. Fungi Causing Opportunistic Mycoses 2-Cryptococcus neoformans
Disease
Cryptococcosis, especially cryptococcal meningitis.
Characteristics
Heavily encapsulated yeast.
Habitat is soil, enriched by pigeon droppings.
Transmission
Inhalation of airborne yeast cells.

38. Fungi Causing Opportunistic Mycoses 2-Cryptococcus neoformans
Pathogenesis
Organisms cause influenza-like syndrome or pneumonia.
They spread via the bloodstream to the meninges.
Reduced cell-mediated immunity severe disease

39. Fungi Causing Opportunistic Mycoses 3-Aspergillus fumigatus
Disease
Invasive aspergillosis
Allergic bronchopulmonary aspergillosis
Aspergilloma (fungus ball).
Characteristics
Mold with septate hyphae (branch at V-shaped angle) .
Habitat is the soil.
Transmission
Inhalation of airborne spores (conidia).

40. Fungi Causing Opportunistic Mycoses 3-Aspergillus fumigatus
Pathogenesis
In immunocompromised patients, invasive disease occurs.
It invades blood vessels thrombosis & infarction.
Person with lung cavity, e.g., from tuberculosis, may develop "fungal ball" (aspergilloma).
Allergic person, can develop allergic bronchopulmonary aspergillosis mediated by IgE antibody.

41. Fungi Causing Opportunistic Mycoses 4-Mucor & Rhizopus Species
Disease
Mucormycosis.
Characteristics
Molds with nonseptate hyphae that typically branch at 90-degree angle (wide-angle branching).
Habitat is soil.
Transmission
Inhalation of airborne spores.

42. Fungi Causing Opportunistic Mycoses 4-Mucor & Rhizopus Species
Pathogenesis
They cause disease primarily in ketoacidotic diabetic and leukemic patients.
Sinuses & surrounding tissue are typically involved.
Hyphae invade mucosa & progress into underlying tissue & vessels, leading to necrosis & infarction.