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ID Unit 3 > Fungal Infections > Flashcards

Fungal Infections Flashcards

1
Q

Tinea - What organisms are responsible?

A

Trichophyton tonsurans (Most common)
Microsporum canis
Trichophyton rubrum

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2
Q

Tinea cruris - What organism is responsible?

A

Trichophyton rubrum

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3
Q

Tinea pedis (Hyperkeratotic form) - What organism is responsible?

A

Trichophyton rubrum

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4
Q

3 presentations of tinea unquium (onchomycosis)

A 
Leukonychia mycotica 
Subungual onchomycosis (distal vs. proximal)
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5
Q

Culture media used to dx fungal infections (2)

A

Sabouraud’s agar

Dermatophyte Test Medium (DTM) = Sabouraud’s + antibiotic + pH color indicator

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6
Q

Risk factors for Candidiasis

A 
Antibiotics
Corticosteroids 
Diabetes Mellitus
Oral contraceptive pills
Pregnancy
Burns
Trauma
Foreign body (catheters) 
Immunosuppression
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7
Q

Tinea versicolor

A

Caused by Malassezia furfur - normal yeast flora of skin and scalp; feeds on sebaceous lipids

Presents as asymptomatic yellow/brown scaly patches; less commonly as hypopigmented patches or folliculitis

Treatment: Topical miconazole

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8
Q

Sporotrichosis - Causative organism

A

Sporothrix schenckii

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9
Q

Sporotrichosis - Clinical Presentation and Treatment

A

Traumatic innoculation of spores into skin (typically by a thorn) causes lymphocutaneous disease characterized by local ulcer with nodules along draining lymphatics (ascending lymphangitis)

Treatment: Itraconazole, potassium iodide

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10
Q

4 classic dimorphic fungi

A

Blastomycosis
Coccidiodomycosis
Paracoccidioidomycosis
Histoplasmosis

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11
Q

Blastomycosis

A

Etiology: Blastomyces dermitiditis

Epidemiology: Mississippi-Ohio River Valley and Central America

Causes inflammatory lung disease; can disseminate to skin and bones, and can form granulomatous nodules

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12
Q

Coccidiodomycosis

A

Etiology: Coccidiodes immitus

Epidemiology: Saprophyte found in Sonoran environments; associated with occupational exposure (agriculture, military, construction)

Causes pneumonia and meningitis; +/- cavitary / granulomatous lung nodules; can disseminate to skin and bone

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13
Q

Paracoccidioidomycosis

A

Etiology: Paracoccidioides brasiliensis

Epidemiology: Saprophyte common to Central/South America

Causes pneumonia; can disseminate to involve skin, lymph nodes, and adrenals

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14
Q

Histoplasmosis

A

Etiology: Histoplasma capsulatum

Epidemiology: Soil saprophyte a/w bird and bat feces; common to chicken farms and caves in the MS-OH River Valley

Causes pneumonia +/- chronic pulmonary cavitations; rarely disseminates causing oropharyngeal ulcers and adrenal involvement

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15
Q

Cryptococcicosis

A

Etiology: Cryptococcus neoformans; mucoid capsule Serotype A responsible for 95% of infections in the US

Epidemiology: Worldwide; a/w pigeon feces

Causes cryptococcal meningitis, an AIDS-defining illness (CD4 < 50)

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16
Q

Aspergillosis

A

Etiology: Aspergilus fumigatus

3 major presentations:

  1. Invasive aspergillosis (immunocompromised)
  2. Allergic bronchopulmonary aspergillosis (asthma, CF); causes bronchiectasis and eosinophilia
  3. Aspergillomas in lung cavities (esp. after TB)

Some species produce aflatoxins, which are associated with hepatocellular carcinoma

17
Q

Why does mucormycosis preferentially affect diabetics in DKA?

A

Rhizopus sp. are thermotolerant, thrive in high concentrations of glucose and ketones, and prefer acid pH

Organisms can proliferate in blood vessels walls when there is an excess of glucose and ketones and penetrate the cribriform plate to enter the brain

18
Q

Mucormycosis

A

Etiology: Rhizopus sp.

Epidemiology: Ubiquitous in decaying organic matter

Presentation is acute and severe with 50% mortality; pre-deliction for diabetics in DKA

Fungi proliferate in blood vessels and penetrate cribriform plate to enter brain; causes rhinocerebral and frontal lobe ascesses, headache, facial pain, black necrotic eschar on face

Treatment: Amphotericin B

19
Q

Microscopic description of mucormycosis

A

Biopsy shows aseptate, right-angle branching

20
Q

Pneumocystosis

A

Etiology: Pneumocystis jiroveci

Epidemiology: Normal flora of the lungs; almost exclusively affects immunocompromised pts

Presents as pneumonia with 15% fatality

CXR shows diffuse peri-hilar infiltrates

21
Q

Systemic Candidiasis - Diagnosis

A

Biopsy - pseudohyphae with yeast

Culture - GMS stain

22
Q

Microscopic description of Blastomyces

A

“Broad-budding yeast”

23
Q

Microscopic description of Aspergillosis

A

Mold with hyphae that branch at 45 degree angles with rare fruiting bodies

24
Q

Microscopic description of Histoplasmosis

A

“Small intracellular yeast” or tiny yeasts inside macrophages

25
Q

Air-crescent sign

A

Pulmonary aspergillosis

26
Q

Microscopic description of Coccidioides

A

Spherules with endospores

27
Q

Microscopic description of Malassezia furfur

A

Spaghetti and meatballs

28
Q

Microscopic description of Candida

A

Dimorphic yeast + pseudohyphae; germ tube positive

29
Q

Treatment of candidiasis

A

Vaginal - Topical -azole (Miconazole)

Oral / esophageal - Fluconazole or Capsofungin

Systemic - Amphotericin B or Capsofungin

30
Q

Microscopic description of Paracoccidioidomycosis

A

Budding yeast with captain’s wheel formation

31
Q

Diagnosis of Pneumocystic jirovecii

A

Disc-shaped yeast on methenamine silver stain of lung tissue

32
Q

Prophylaxis of PCP

A

Indicated when CD4 < 200 in HIV patients

TMP-SMX
Dapsone
Atovaquone

33
Q

Microscopic definition of Sporothrix schenckii

A

Dimorphic, cigar-shaped budding yeast

34
Q

Diagnosis of cryptococcal meningitis

A

India ink stain of CSF shows encapsulated yeasts with wide capsular halos and unequal budding

Mucicarmine stains capsule red

Latex agglutination test detects polysaccharide capsular antigen

ID Unit 3 (9 decks)

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