Fungi Flashcards
Fungal versus mammalian plasma membrane sterols
Ergosterol (important target for antifungal therapy) versus cholesterol
Fungal cell wall composition
Glucan and chitin
Fungal virulence factors
Cell wall, exoenzymes/toxins
Fungi: Dimorphism two growth forms
Molds or yeasts
How do molds grow
Hyphae (Microscopic, branching, thread-like filaments) -> Mycelium
Hyphae two types
Septate (divided by cross walls)
Nonseptate and multinucleate
Yeast description
Single, ovoid, or spherical cells with a rigid cell wall
Candida morphogenesis
Present as yeast form but can elongate as hypha like structure (germ-tube)
Fungal virulence factors
Thermotolerance, cell wall components, exoenzymes, toxins
Host risk factors for fungal infection
Immunosuppression (neutropenia, cell-mediated immune dysfunction), previous antibiotic use, warm/wet environment, malnutrition, extremes of age, indwelling catheters/hardware
Fungal disease pathogenesis
Adherence, invasion, local tissue destruction, immunogenic cell wall (e.g. hypersensitivity to cell wall components)
What are the endemic fungi (with location)? Detection?
Histoplasma - Ohio-Mississippi River Valley
Blastomyces - North Central U.S.
Coccidioides - Southern U.S. and Latin America
Antigen detection helpful
Coccidioides still use serology (but generally not very useful)
What cause mild cutaneous fungal infections?
Trichophyton, Epidermophyton, Microsporum
What is KOH used for?
Body fluids, cervical/vaginal swab
Antifungal therapy
Polyenes - amphotericin B bind ergosterol (significant toxicity), currently enclosed in liposomes to make it safer, tends to be second-line
First line antifungal therapy - azoles inhibit ergosterol synthesis, rather safe
Allylamines - terbinafine topical antifungal, inhibits earlier step in sterol synthesis (has liver toxicity when taken orally)
Echinocandins - newest group, end in fungin, inhibit cell wall glucan synthesis, only IV use, predominantly used to treat candida (increasing azole resistance)
Fungal site of infections
Superficial, cutaneous, subcutaneous, pulmonary, bloodstream, meningitis
Superficial mycoses - where, what species
Involve stratum corneum, malassezia furfur
Superficial mycoses - what does it cause, treatment
Chronic hypo or hyperpigmentation (pityriasis versicolor), superficial skin infection, generally treated with topical therapy
Cutaneous mycoses - what does it cause
Tinea family (capitis, pedis, cruris, corporis, manus), dermatophytosis, onychomycosis
Cutaneous mycoses treatment
Topical azoles, systemic azoles, terbinafine, griseofulvin
Subcutaneous mycoses - species, what does it cause
Sporotrichosis - nodular lesion with lymphatic spread (“Rose gardener’s disease”)
Subcutaneous mycoses treatment
Itraconazole
Endemic mycoses causative agents
Thermally dimorphic fungi (hyphal form in environment, yeast form in tissue)
How are endemic mycoses acquired
Inhalation -> pulmonary infection -> dissemination (potentially)
Histoplasmosis - what does it cause
Vast majority of primary infection is subclinical
Complications - Pulmonary calcifications, mediastinal lymphadenitis, mediastinal fibrosis
Histoplasmosis - characteristic tissue response
Caseating or noncaseating granulomas (also for TB)
Histoplasmosis treatment
Amphotericin B, Itraconazole
Blastomycosis - where does it disseminate
Skin and bone
Blastomycosis - typical inflammatory response
Clusters of neutrophils and noncaseating granulomas
Blastomycosis diagnosis
Broad-based budding yeast
Candidiasis: Types of infections
Mucocutaneous infection (thrush, vulvovaginal candidiasis, esophageal candidiasis) Invasive infection (candidemia)
What is candida auris associated with
Nosocomial transmission and outbreaks in healthcare settings, multi-drug resistance
Cryptococcosis: What does it have a predilection for
CNS
Cryptococcosis virulence factor
Polysaccharide capsule - produces brain edema, polysaccharide plug up arachnoid villi
When use 5-flucytosine
Initial therapy for cryptococcosis (along with amphotericin B)
How get cryptococcosis
Inhaled and disseminates
How get aspergillosis
Inhaled
What aspergillosis cause
Pneumonia, sinusitis, disseminated infection
Aspergillosis histopathology
Septate hyphae, acute angle branching
Mucormycosis - how get it
Environmental organisms get inhaled - right circumstances can cause disease
Mucormycosis histopathology
Broad, non-septate, right-angle branching
Mucormycosis - what does it cause
Pneumonia, rhino-orbital, cerebral disease
