Fungi Flashcards
Presentation and pathogenesis of Cryptococcus neoformans
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
Presentation and pathogenesis of Chromoblastomycosis
Following trauma, chronic infection of subcutaneous tissue.
Diagnosis and morphology of Chromoblastomycosis
Cauliflower-like lesions on lower extremities.
Diagnosis and morphology of Blastomyces dermatitidis
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
Presentation and pathogenesis of Histoplasma capsulatum
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.
Presentation and pathogenesis of Candida albicans
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
Presentation and pathogenesis of Sporothrix schenckii
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
Presentation and pathogenesis of Coccidioidomycosis
Desert climate (southwest US). Inhaled arthroconidia convert to spherules in monocytes. Causes fever, cough, chest pain, malaise. Can disseminate to bone.
Diagnosis and morphology of Cryptococcus neoformans
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
Presentation and pathogenesis of Mucormycosis/Rhizopus arrhizus
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)
Diagnosis and morphology of Aspergillus fumigatus
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
Presentation and pathogenesis of Aspergillus fumigatus
Rapidly growing mold found in soil, air, dust. Spores are inhaled, attach to fibronectin. Alternative complement pathway is inhibited, preventing opsonization
Diagnosis and morphology of Coccidioidomycosis
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
Presentation and pathogenesis of Dermatophytes
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
Diagnosis and morphology of Dermatophytes
KOH or calcofluor stain of leading edge of skin lesion. Hair will fluoresce under Wood’s lamp (UV light).
Diagnosis and morphology of Candida krusei
Resistant to antifungals.
Diagnosis and morphology of Candida dubliniensis
Germ tube positive. Produces asexual spore, chlamydospores at terminal ends of pseudohyphae, usually in pairs
Presentation and pathogenesis of Blastomyces dermatitidis
Found in soil and wood in the central US (Chicago is epicenter). Inhalation leading to pulmonary, skin, lytic bone lesions and disseminated disease
Presentation and pathogenesis of Candida dubliniensis
Often found in oral or fecal specimens of HIV+ patients.
Presentation and pathogenesis of Candida krusei
Colonize/infection seen in bone marrow transplant patients.
Diagnosis and morphology of Mucormycosis/Rhizopus arrhizus
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.
Diagnosis and morphology of Histoplasma capsulatum
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
Diagnosis and morphology of Sporothrix schenckii
ID on culture and microscopy of mold. Dimorphic fungus with cigar shaped yeast, mold with daisy-like conidiophore
Diagnosis and morphology of Candida albicans
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
