Fungi

Question 1

Presentation and pathogenesis of Cryptococcus neoformans

Answer 1

Associated with pigeon droppings and soil. Patients present with meningitis (headache, nausea, gait problems, dementia, iritability, CN abnormalities). The only encapsulated yeast.. Inhalation from environmental source causes pulmonary infection. Capsule blocks phagocytosis and prevents complement activation. Hematogenous spread to CNS occurs in immuncompromised patients

Question 2

Presentation and pathogenesis of Chromoblastomycosis

Answer 2

Following trauma, chronic infection of subcutaneous tissue.

Question 3

Diagnosis and morphology of Chromoblastomycosis

Answer 3

Cauliflower-like lesions on lower extremities.

Question 4

Diagnosis and morphology of Blastomyces dermatitidis

Answer 4

CXR showing alveolar/nodular infiltrates. GMS or PAS stain used to see yeast like cells. Conidiophores arise at right angles to hyphae (lollipop). Dimorphic. Large thick wall yeasts with BROAD BASED BUDS

Question 5

Presentation and pathogenesis of Histoplasma capsulatum

Answer 5

Found in soil, bird, bat droppings in the Ohio/Mississippi river valleys. Inhaled and converts to yeast which multiply and spread to liver, spleen, bone marrow. Primary lesion is a granuloma in the lung.

Question 6

Presentation and pathogenesis of Candida albicans

Answer 6

Normal flora in GI and GU tracts. Infectious in patients with defects in cell-mediated imunity, neutropenia. Adheres to mucosal cells, produces phospholipases, binds C3b to prevent opsonization. Opportunistic: infects after ABX therapy, corticosteroid use, immune compromise, diabetes

Question 7

Presentation and pathogenesis of Sporothrix schenckii

Answer 7

Found in soil. Related to gardening, rose thorns, moss. Subcutaneous infection. . Inhaled conidia or traumatic inoculation. Firm nodules form along lymphatics. Can disseminate to bones, lungs, eyes and CNS

Question 8

Presentation and pathogenesis of Coccidioidomycosis

Answer 8

Desert climate (southwest US). Inhaled arthroconidia convert to spherules in monocytes. Causes fever, cough, chest pain, malaise. Can disseminate to bone.

Question 9

Diagnosis and morphology of Cryptococcus neoformans

Answer 9

CXR will show one or more well localized infiltrates. Patients may have raised skin lesions. Culture cream/pink/yellow/brown dull colonies grow at 37C. Yeast with a polysaccharide capsule

Question 10

Presentation and pathogenesis of Mucormycosis/Rhizopus arrhizus

Answer 10

Angiotropic infection in immune compromised individuals, DKA patients. Acute and rapidly fatal invasion of major blood vessels causing necrosis and infarction of adjacent tissues. Spores are inhaled, deposit in the nasal turbinates. Infection typically involves rhino-facial-cranial area (invades sinuses and orbits)

Question 11

Diagnosis and morphology of Aspergillus fumigatus

Answer 11

Visible with silver stain. Allergic aspergillosis diagnosed by IgE/IgG levels, sputum culture, skin test. Fungus ball can be seen in pre-exisitng cavity. Dichotomous branching (45 degrees) septate hyphae

Question 12

Presentation and pathogenesis of Aspergillus fumigatus

Answer 12

Rapidly growing mold found in soil, air, dust. Spores are inhaled, attach to fibronectin. Alternative complement pathway is inhibited, preventing opsonization

Question 13

Diagnosis and morphology of Coccidioidomycosis

Answer 13

CXR shows infiltrate, hilar LAD, pleural effusion. Can have erythema nodosum. Spherules detected microscopically. Skin test positive 1-4wks. At 25C, arthroconidia are seen (alternating barrel pattern). Dimorphic: spherule with endospores in tissue, mold in culture

Question 14

Presentation and pathogenesis of Dermatophytes

Answer 14

Cause fungal infection of keratinized tissues (skin, hair, nails). Causes circular erythematous ring that expands. Infection begins in damp areas like feet (Tinea pedis). Inoculated via minor trauma. Fungi have keratinase, which promotes spread of infection laterally. Cell mediated immunity should resolve

Question 15

Diagnosis and morphology of Dermatophytes

Answer 15

KOH or calcofluor stain of leading edge of skin lesion. Hair will fluoresce under Wood’s lamp (UV light).

Question 16

Diagnosis and morphology of Candida krusei

Answer 16

Resistant to antifungals.

Question 17

Diagnosis and morphology of Candida dubliniensis

Answer 17

Germ tube positive. Produces asexual spore, chlamydospores at terminal ends of pseudohyphae, usually in pairs

Question 18

Presentation and pathogenesis of Blastomyces dermatitidis

Answer 18

Found in soil and wood in the central US (Chicago is epicenter). Inhalation leading to pulmonary, skin, lytic bone lesions and disseminated disease

Question 19

Presentation and pathogenesis of Candida dubliniensis

Answer 19

Often found in oral or fecal specimens of HIV+ patients.

Question 20

Presentation and pathogenesis of Candida krusei

Answer 20

Colonize/infection seen in bone marrow transplant patients.

Question 21

Diagnosis and morphology of Mucormycosis/Rhizopus arrhizus

Answer 21

Culture will rapidly grow woolly white/grey mold, will have characteristic sporangia. Black nasal discharge. PAS stain shows ribbon-like hyphae with 90 degree branching pattern. Almost no septae visible.

Question 22

Diagnosis and morphology of Histoplasma capsulatum

Answer 22

Urine antigen test is done most commonly. Slow growing colony that is white initially, turns brown with age. Dimorphic: yeast in macrophages, mold phase with tuberculate macroconidia

Question 23

Diagnosis and morphology of Sporothrix schenckii

Answer 23

ID on culture and microscopy of mold. Dimorphic fungus with cigar shaped yeast, mold with daisy-like conidiophore

Question 24

Diagnosis and morphology of Candida albicans

Answer 24

Mucocutaneous infection seen (thrush, vulvovaginosis, diaper rash). Visible on gram stain, calcofluor stain, PAS stain. Germ tube positive. Culture: dull white colonies. Clusters of round blastoconidia along hyphae. Pseudohyphae are the invasive form. Produces asexual spore, chlamydospores