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Flashcards in Mycology I Deck (33):
1

What components of the innate immune system are largely responsible for protection against fungal infections

Professional phagocytes (neutrophils, macrophages and dendritic cells), the complement system, and PRR

2

Humoral immunity against fungi

- Antibodies can be detected during most fungal infections
- There is little evidence that an antibody response contributes to immunity against most fungi

3

Cellular immunity against fungi

- If fungal cells escape phagocytosis, then the dominant effect occurs through the interaction of dendritic cells and macrophages that results in the production of IL-12 and IFN-γ, leading CD4 cells to differentiate to Th1 cells
- Subsequently, macrophages containing multiplying fungi are activated by cytokine mediators that are produced by T-lymphocytes that have encountered fungal antigens
- Infection ultimately controlled by activated macrophages

4

Superficial mycoses

Malassezia furfur
Hortaea werneckii/ Exophiala Werneckii
Piedraia hortae
Trichosporon

5

Cutaneous mycoses

Dermatophytes: Trichophyton, Epidermophyton and Microsporum

6

Subcutaneous Mycoses

Sporothrix schenckii

7

Opportunistic Mycosis

Pneumocystis jirovecii
Pneumocystis carinii

8

Malassezia furfur
Infection/disease:
Morphology:
Epidemiology:

Infection/disease: Pitryiasis (Tinea) versicolor
Morphology: Lipophilic yeast; hyphae produced infrequently; growth in cultures requires source of lipid
Epidemiology: Tropical and subtropical regions; not found as saprophyte in nature; passed between humans by direct or indirect transfer of infected keratinous material

9

Malassezia furfur
Clinical syndromes:
Laboratory Diagnosis:
Treatment:

Clinical syndromes: Small hypopigmented or hyperpigmented macules; affected areas don't tan
Laboratory Diagnosis: Direct microscopic visualizations in KOH preparation; calcofluor white also used to visualize; Wood lamp - lesions fluoresce a yellow color
Treatment: Spontaneous resolution not likely; localized infection treat with topical azoles or selenium sulfide shampoo

10

Hortaea Werneckii/ Exophiala Werneckii
Infection/Disease:
Morphology:

Infection/Disease: Responsible for Tinea nigra
Morphology: Dematiaceous (dark colored) frequently branched hyphae
- In culture on standard mycologic medium at 25° a black mold with annelloconidia observed

11

Hortaea Werneckii/ Exophiala Werneckii
Epidemiology:
Clinical Syndromes:
Laboratory Diagnosis:
Treatment:

Epidemiology: Dark warm moist environment; Africa, Asia, and Central and South America; contracted by inoculation into superficial layers of the epidermis
Clinical Syndromes: Solitary, irregular, pigmented macule, usually on palms or soles; can resemble malignant melanoma (not contagious)
Laboratory Diagnosis: Direct microscopic visualization in KOH preparation
Treatment: Responds well to topical agents: azoles and terbinafine

12

Piedraia Hortae
Infection/Disease:
Morphology:
Epidemiology:

Infection/Disease: Responsible for black piedra
Morphology: Brown to reddish black mold that exhibit asci (sexual spores) as the culture ages
Epidemiology: Uncommon, but can be found in Latin America and Central Africa (poor hygiene)

13

Piedraia Hortae
Clinical syndromes:
Laboratory Diagnosis
Treatment:

Clinical Syndromes: The presence of hard dark nodules that surround the hair shaft; asci present in cement-like substance that holds the hyphal mass together
Laboratory Diagnosis: Cultivated on routine mycological medium at 25°C
Treatment: Can be cured with a haircut, proper/regular washings and topical antifungal agents

14

Trichosporon: T. Inkin, T. asahii and/or T. mucoides
Infection/Disease:
Morphology:
Epidemiology:
Clinical Syndromes:

Infection/Disease: Responsible for white Piedra
Morphology: Yeast-like fungus; hyphal elements
Epidemiology: Occurs in tropical and subtropical regions (poor hygiene)
Clinical Syndromes: Affects hair of groin and axillae; fungus surrounds hair shaft and forms white brown swelling

15

Trichosporon: T. Inkin, T. asahii and/or T. mucoides
Laboratory Diagnosis:
Treatment:

Laboratory Diagnosis: If microscopic examination reveals hyphal elements, arthroconidia and/or budding yeast, hair shaft can be cultures on mycologic media without cycloheximide (inhibits growth of Trichosporon); In culture, exhibits cream-colored, dry, wrinkled colonies
Treatment: Removal of infected hair, improved hygiene and topical azoles agents

16

Dermatophytes/Dermatophytoses
Infection/Disease:

- Very similar and closely related group of fungi that cause a wide variety of clinical disease
- Approximately 41 species of fungi recognized as dermatophytes
- All have the ability to infect superficial keratinized tissues

17

Tineas or ringworms (Dermatophytoses)

- Tinea capitis-scalp (Endothrix-arthroconidia inner hair shaft; Ectothrix-arthoconidia - outer hair shaft; favic)
- Tinea pedis-foot
- Tinea barbae - beard
- Tinea corporis - smooth of glabrous skin
- Tinea Cruris - groin
- Tinea unguium - nails

18

Dermatophytes - Morphology

The pattern of growth observed in culture along with the production/appearance of macroconidia and microconidia are distinct for each genus
- Microscopic examination of infected skin exhibit hyaline septate hyphae, chains of arthroconidia and dissociated arthrocondia
- Most unable to grow at 37° or w/ serum

19

Production of Macroconidia or microconidia
Epidermophyton:
Microsporum:
Trichophyton:

Epidermophyton: Macroconidia
Microsporum: Macroconidia and Microconidia (rare)
Trichophyton: Macroconidia (rare) and microconidia

20

Dermatophytes - Ecology (Three categories)

Zoophilic - animals
Geophilic - soil (Strong host response - highly inflamed lesions)
Anthrophilic - humans (Chronic infection with mild host response that can be difficult to cure)

21

Which two dermatophytes account for 80-90% of worldwide infections

Trichophyton rubrum and T. Mentagrophytes

22

Dermatophytes - Clinical Symptoms:

- Tinea pedis will exhibit itching vesicles and pustules, cracked skin, peeling, watery discharge
- Tinea coporis and Tinea cruris can exhibit a tiny red pimple, with itching and subsequent peripheral spreading
- Tinea capitis will spread peripherally with patches of broken hair stumps
- Tinea unguium - nails will appear thickened, cracking and have yellowish-brown color

23

Dermatophytes - Laboratory Diagnosis:

- Direct microscopic observation of specimens
- Some fluoresce a distinct color when exposed to a wood lamp
- Cultured on dermatophyte test media
Phenol red pH indicator included which changes from yellow to red when medium becomes alkaline from dermatophytes

24

Dermatophytes - Treatment

- For infections that do not involve the hair or nails, topical antifungal agents are usually effective
- For chronic skin infections involving T. rubrum - oral antifungal agents may be necessary
- For infections involving hair and nails - oral antifungal agents usually administered
- For infections of the nail - PinPoint laster therapy

25

Sporothrix Schenckii (Most common Fungal infection in US)
Infection/Disease:

- Responsible for lymphocutaneous sporotrichosis
- Inoculation occurs through traumatic introduction through the dermis
- Found in soil and decaying matter

26

Sporothrix Schenckii- Morphology:

Thermally dimorphic fungus (mold at room temp; yeast at body temp)
Mold exhibits tan, brown, or black color with hyaline, septate hyphae
Yeast form spheric, oval or elongated
- Rarely seen on histological exam of tissue

27

Sporothrix Schenckii - Epidemiology

Usually sporadic infection and occurs in warmer climates
- Major endemic areas are Japan, NA and SA

28

Sporothrix Schenckii - Clinical Syndromes

Usually the primary site of inoculation is non or mildly painful and will appear as nodular lesion that will eventually ulcerate
- The infection can spread through the lymphatics that drain the site

29

Sporothrix Schenckii - Laboratory Diagnosis

Culturing leads to most definitive diagnosis
Incubating the plate at room temp for 2-4 days will lead to growth of mold
37° will lead to growth of yeast

30

Sporothrix Schenckii - Treatment

In developing countries - Potassium iodide solution
- Potassium Iodide has adverse side effects including nausea and salivary gland enlargement
- Itraconazole is safe and effective but must be administered for 3-6 mo

31

Pneumocystis lifecycle

Organism has never been grown in vitro
- Cystic structure that contains elliptical subunits that grow and repeat the cycle on rupture
- Three stages: trophic, precyst, and cyst
- Trophic form surrounded by a cell wall and plasma membrane containing a nucleus and several mitochondria
- The precyst subsequently matures into a cyst which contains 8 "spores"

32

Pneumocystis jirovecci/ Pneumocystis carinii - Epidemiology

All individuals are exposed to this organism - most seropositive by age 4
Active infections rare
Patients at risk when CD4+ T cells fall below 200 cells/mm³

33

Pneumocystis jirovecci/ Pneumocystis carinii - Clinical Disease:
Laboratory Diagnosis:

Clinical Disease:
- Insidious onset of pneumonia
- Presents as severe progressive interstitial pneumonia
- Frothy pulmonary edema with cellular infiltrate
- Mortality rate high among untreated patients
Laboratory Diagnosis: Microscopic identification of organism in sputum, bronchoscopy, bronchoalveolar lavage sample