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IAHI Block 1 > Mycology I > Flashcards

Mycology I Flashcards

1
Q

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

A

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

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2
Q

Humoral immunity against fungi

A
  • Antibodies can be detected during most fungal infections

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

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3
Q

Cellular immunity against fungi

A
  • 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
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4
Q

Superficial mycoses

A

Malassezia furfur
Hortaea werneckii/ Exophiala Werneckii
Piedraia hortae
Trichosporon

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5
Q

Cutaneous mycoses

A

Dermatophytes: Trichophyton, Epidermophyton and Microsporum

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6
Q

Subcutaneous Mycoses

A

Sporothrix schenckii

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7
Q

Opportunistic Mycosis

A

Pneumocystis jirovecii

Pneumocystis carinii

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8
Q

Malassezia furfur
Infection/disease:
Morphology:
Epidemiology:

A

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

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9
Q

Malassezia furfur
Clinical syndromes:
Laboratory Diagnosis:
Treatment:

A

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

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10
Q

Hortaea Werneckii/ Exophiala Werneckii
Infection/Disease:
Morphology:

A

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

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11
Q 
Hortaea Werneckii/ Exophiala Werneckii
Epidemiology:
Clinical Syndromes:
Laboratory Diagnosis:
Treatment:
A

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

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12
Q

Piedraia Hortae
Infection/Disease:
Morphology:
Epidemiology:

A

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)

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13
Q

Piedraia Hortae
Clinical syndromes:
Laboratory Diagnosis
Treatment:

A

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

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14
Q 
Trichosporon: T. Inkin, T. asahii and/or T. mucoides
Infection/Disease:
Morphology:
Epidemiology:
Clinical Syndromes:
A

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

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15
Q

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

A

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

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16
Q

Dermatophytes/Dermatophytoses

Infection/Disease:

A
  • 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
Q

Tineas or ringworms (Dermatophytoses)

A
  • 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
Q

Dermatophytes - Morphology

A

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
Q

Production of Macroconidia or microconidia
Epidermophyton:
Microsporum:
Trichophyton:

A

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

20
Q

Dermatophytes - Ecology (Three categories)

A

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
Q

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

A

Trichophyton rubrum and T. Mentagrophytes

22
Q

Dermatophytes - Clinical Symptoms:

A
  • 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
Q

Dermatophytes - Laboratory Diagnosis:

A
  • 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
Q

Dermatophytes - Treatment

A
  • 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
Q 
Sporothrix Schenckii (Most common Fungal infection in US)
Infection/Disease:
A
  • Responsible for lymphocutaneous sporotrichosis
  • Inoculation occurs through traumatic introduction through the dermis
  • Found in soil and decaying matter
26
Q

Sporothrix Schenckii- Morphology:

A

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
Q

Sporothrix Schenckii - Epidemiology

A

Usually sporadic infection and occurs in warmer climates

- Major endemic areas are Japan, NA and SA

28
Q

Sporothrix Schenckii - Clinical Syndromes

A

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
Q

Sporothrix Schenckii - Laboratory Diagnosis

A

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
Q

Sporothrix Schenckii - Treatment

A

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
Q

Pneumocystis lifecycle

A

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
Q

Pneumocystis jirovecci/ Pneumocystis carinii - Epidemiology

A

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
Q

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

A

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

IAHI Block 1 (16 decks)

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