Mycology I

Question 1

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

Answer 1

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

Question 2

Humoral immunity against fungi

Answer 2

• Antibodies can be detected during most fungal infections

- There is little evidence that an antibody response contributes to immunity against most fungi

Question 3

Cellular immunity against fungi

Answer 3

• 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

Question 4

Superficial mycoses

Answer 4

Malassezia furfur
Hortaea werneckii/ Exophiala Werneckii
Piedraia hortae
Trichosporon

Question 5

Cutaneous mycoses

Answer 5

Dermatophytes: Trichophyton, Epidermophyton and Microsporum

Question 6

Subcutaneous Mycoses

Answer 6

Sporothrix schenckii

Question 7

Opportunistic Mycosis

Answer 7

Pneumocystis jirovecii

Pneumocystis carinii

Question 8

Malassezia furfur
Infection/disease:
Morphology:
Epidemiology:

Answer 8

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

Question 9

Malassezia furfur
Clinical syndromes:
Laboratory Diagnosis:
Treatment:

Answer 9

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

Question 10

Hortaea Werneckii/ Exophiala Werneckii
Infection/Disease:
Morphology:

Answer 10

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

Question 11

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

Answer 11

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

Question 12

Piedraia Hortae
Infection/Disease:
Morphology:
Epidemiology:

Answer 12

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)

Question 13

Piedraia Hortae
Clinical syndromes:
Laboratory Diagnosis
Treatment:

Answer 13

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

Question 14

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

Answer 14

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

Question 15

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

Answer 15

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

Question 16

Dermatophytes/Dermatophytoses

Infection/Disease:

Answer 16

• 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

Question 17

Tineas or ringworms (Dermatophytoses)

Answer 17

• 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

Question 18

Dermatophytes - Morphology

Answer 18

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

Question 19

Production of Macroconidia or microconidia
Epidermophyton:
Microsporum:
Trichophyton:

Answer 19

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

Question 20

Dermatophytes - Ecology (Three categories)

Answer 20

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

Question 21

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

Answer 21

Trichophyton rubrum and T. Mentagrophytes

Question 22

Dermatophytes - Clinical Symptoms:

Answer 22

• 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

Question 23

Dermatophytes - Laboratory Diagnosis:

Answer 23

• 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

Question 24

Dermatophytes - Treatment

Answer 24

• 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

Question 25

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

Answer 25

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

Question 26

Sporothrix Schenckii- Morphology:

Answer 26

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

Question 27

Sporothrix Schenckii - Epidemiology

Answer 27

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

Question 28

Sporothrix Schenckii - Clinical Syndromes

Answer 28

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

Question 29

Sporothrix Schenckii - Laboratory Diagnosis

Answer 29

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

Question 30

Sporothrix Schenckii - Treatment

Answer 30

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

Question 31

Pneumocystis lifecycle

Answer 31

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"

Question 32

Pneumocystis jirovecci/ Pneumocystis carinii - Epidemiology

Answer 32

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

Question 33

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

Answer 33

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