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Microbiology Exam 1 > Mycology > Flashcards

Mycology Flashcards

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1
Q

What are the fungi types?

A

1) Yeasts: grow as single cells
2) Molds: grow as long hyphae and form a mat (mycelium)

  • Are eukaryotic (bacteria are prokaryotic)
  • Require an aerobic environment and a carbon source
  • Their natural habitat is the environment, except Candida albicans
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2
Q

What are fungi virulence factors?

A

1) Capsule – Antiphagocytic. Can be visualized with India ink staining
2) Cell wall - Made of chitin (polysaccharide)
- Some anti-fugal agents work by inhibiting these polysaccharides
3) Cell membrane – Contains ergosterol (human cell membranes contain cholesterol)
- Most antifungal agents work by disrupting ergosterol

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3
Q

Describe yeasts.

A
  • Unicellular form, round or ellipse
  • Reproduce by budding – asexual reproduction
  • If buds don’t separate, they form long chains of yeast cells called pseudohyphae
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4
Q

Describe molds.

A
  • Multicellular colonies made of clumps of intertwined branching hyphae (mycelia)
  • Grow by extending in length
  • Produce spores – reproducing bodies of molds
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5
Q

What is dimorphism?

A
  • They form different structures at different temperatures

- They are molds at ambient temperature and yeasts in human tissue at body temperature

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6
Q

How are fungi organized?

A
  • Fungal diseases are organized by the depth of the skin they infect
  • Superficial
  • Cutaneous
  • Subcutaneous
  • Systemic
  • Opportunistic
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7
Q

What are the superficial fungal infections?

A

Pityriasis versicolor (tinea versicolor)

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8
Q

Pityriasis versicolor (tinea versicolor) details.

A
  • Etiology: Malassezia furfur
  • Occurs more in hot, humid weather, but it is part of normal skin flora
  • Physical exam: Hypopigmented or hyperpigmented patches, +/- itching. UV exposure causes skin around patches to tan
  • Diagnosis: KOH
  • “Spaghetti and meatballs” –> budding yeast (spherical) and hyphae
  • Treatments: topical antifungals
  • Miconazole cream (Desenex, Zeasorb)
  • Topical imidazole (ketoconazole shampoo – Nizoral)
  • Selenium sulfide shampoo (Selsun Blue) or zinc shampoo (DHS)
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9
Q

What are the two groups of cutaneous fungal infections?

A

1) Dermatophytes: Infect Skin, Hair, Nails (karotin)

2) Candida: Infect skin

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10
Q

What fungal infections fall under the Dermatophytes group?

A
  • Trichophyton
  • Epidermophyton
  • Microsporum
  • Tinea corporis - body (red raised border of active inflammation with a healing center)
  • Tinea cruris – groin and scrotum
  • Tinea pedis – foot
  • Tinea capitis – scalp (Primarily in children)
  • Tinea unguium (onychomycosis) – nails
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11
Q

What fungal infections fall under the Candida group?

A
  • Candida albicans
    - Mouth – Oral thrush: Creamy white exudate on reddish base. Hard to scrape off with tongue blade
    - Vagina – Candida vaginitis: Cottage-cheese patches/discharge
    - Groin – Diaper rash: SATELLITE LESIONS
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12
Q

What kind of damage can Candida fungi do in immunocompromised individuals?

A
  • Esophagitis: Substernal chest pain, worse with swallowing

- Disseminated (invasive systemic disease): Can invade blood and every organ

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13
Q

How do you diagnose and treat Dermatophytes?

A
  • KOH: branched hyphae
  • Culture: hyphae, spores
  • Wood’s light: Certain species of Microsporum will fluoresce bright green
  • Topical antifungal creams: Terbinefine, miconazole
  • Oral agents: Terbinafine, fluconazole, itraconazole
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14
Q

How can Candida fungi be identified and treated?

A
  • Candida is normal flora in the GI tract, vagina, and oropharynx
  • Candida in blood is never normal
  • KOH of skin
  • Stains/culture of tissue

-Treatment: IV antifungal therapy (amphotericin B, fluconazole)

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15
Q

Describe subcutaneous fungal infection.

A
  • Etiologic agent: Sporothrix schenckii (sporotrichosis)
  • Normal organism in soil and on plants (ROSE THORNS)
  • Enters body after trauma to the skin
  • Can stay within skin or can spread along lymphatics to local nodes
  • Dimorphic
  • Gardeners are at risk
  • Forms subcutaneous nodule that becomes necrotic and ulcerated

-Treatment is oral itraconazole (Sproanox)

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16
Q

What are the systemic disease in humans?

A

1) Histoplasma capsulatum
2) Blastomyces dermatitidis
3) Coccidioides immitis

17
Q

Describe general characteristics of systemic fungal infections.

A
  • Inhalation of spores from dimorphic fungi
  • Normal habitat is soil - grow as mold and release spores into the air
  • Within the lungs, spores become yeasts
  • Most infections are asymptomatic but can disseminate to other organs
  • Not contagious person to person
18
Q

Histoplasma capsulatum details.

A
  • Mississippi and Ohio rivers
  • In soil with BIRD and BAT droppings; nitrogen-rich soil
  • Mold spores float from soil to lung alveoli – presents as a pulmonary infection
  • Spores get engulfed by macrophages and become yeast
  • Most people have silent disease, but it can become disseminated
  • Blood, tissue, and urine can be tested
19
Q

Blastomyces dermatitidis details.

A
  • Mississippi and Ohio river valleys, Great Lakes
  • In soil and DECOMPOSING WOOD and LEAVES
  • Spores are breathed in and asymptomatic cases are rarely recognized
  • Can disseminate to skin and bone
  • Diagnosis: biopsy, PCR assay
  • Treated with amphotericin B, itraconazole
20
Q

Coccidioides immitis details.

A

-Endemic to southwest – AZ, NM, CA, Mexico
“Valley Fever” or “Desert Rheumatism”
-Inhalation of spores from soil
-Become spherules containing endospores in lung
-Local infection of lung is followed by infection of blood –> Usually destroyed at this point by cell-mediated immune system in immunocompetent host

21
Q

Clinical presentations of Coccidioides immitis.

A
  • Asymptomatic
  • Mild URI
  • Pneumonia (most mild) – fever, cough, infiltrates on CXR
  • Disseminated – spread to brain, bone
  • Common opportunistic infection in AIDS patients
22
Q

Diagnostic of of Coccidioides immitis.

A

-Skin test like a PPD
-When injected intradermally, an infected person will have a reaction in 1-2 days (delayed hypersensitivity reaction)
Skin test is positive within 2-4 weeks and stays positive for years
-Blood, tissue (biopsy), sputum tests
-Chest x-ray

23
Q

Treatment of of Coccidioides immitis.

A

-Amphotericin B, azole antifungals (ketoconazole, itraconazole, fluconazole) for persistent infection or disseminated disease

24
Q

What are the groups of opportunistic fungal infections and their Etiologic agents?

A

Cryptococcosis - Cryptococcus neoformans
Aspergillosis - Aspergillus fumigatus
Mucormycosis - Rhizopus species
Pneumocystis jirovecii

25
Q

Cryptococcosis details.

A
  • Etiologic agent: Cryptococcus neoformans
  • Yeast (not dimorphic) with wide capsule
  • In soil containing PIGEON droppings
  • Inhaled into lungs then can spread to brain via blood
  • Most common life-threatening fungal disease in AIDS patients
26
Q

Disease and diagnostics for Cryptococcosis

A

Disease can manifest as

1) Lung infection - asymptomatic or can become pneumonia
2) Meningitis - Headache, nausea, confusion, CN deficits

Diagnosis:

  • Visualize yeast in spinal fluid – India ink
  • Serologic test for antigen and antibody
  • Can test spinal fluid for capsular antigens (cryptococcal antigen test) or culture spinal fluid
27
Q

Aspergillosis details.

A
  • Etiologic agent: Aspergillus fumigatus
  • Mold with spores, not dimorphic
  • Grows in nature on DECAYING VEGITATION
  • Can cause infection of the skin, eyes, ears, and lungs
  • Can colonize and invade abraded skin, wounds, burns, eyes, ears, or sinuses
  • For lung infections - humans inhale the spores
28
Q

What are the types of pulmonary disease caused by aspergillosis?

A

1) ABPA Allergic reaction in airway like asthma: Cough up BROWNISH phlegm containing hyphae
2) Infection in lung: Aspergilloma – fungal ball in lung cavity
3) Invasive lung infection – invasive aspergillosis

29
Q

Treatment of aspergillosis.

A

1) Allergic bronchopulmonary aspergillosis:
- Systemic steroids + Oral antifungal agents
2) Aspergilloma
- Surgical removal
3) Invasive aspergillosis –> High mortality
- Antifungal medications

30
Q

Mucormycosis details

A
  • Etiologic agent: Rhizopus species
  • Mold in environment, not dimorphic
  • After being inhaled, spores cause blood vessel invasion
  • Goes into the blood vessels and clogs it up
  • Infarction of tissue distal to blockage
  • Sinuses, lungs, gut

Causes opportunistic infection in Diabetics, Burn patients, + Immunocompromised

Treatment: surgery and antifungal medication

31
Q

Pneumocystis jirovecii details.

A

In immunocompromised host (AIDS, cancer, organ transplant patients): causes severe pneumonia

  • Most common opportunistic infection in AIDS patients*
  • Fever, shortness of breath, cough
  • Treated with trimethoprim-sulfamethoxazole
  • Prophylactic antibiotics are given to prevent this

Microbiology Exam 1 (7 decks)

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