Wk16D1 Fungi Basics Flashcards
8 Virulence factors
Cell wall, capsules, proteases, lipases, toxins, melanin, adhesins, biofilms
Fungal plasma membrane and cell wall components.
Plasma membrane contains ergosterol.
Cell wall contains chitin (polysaccharide), other polysaccharides (B-glucan), and other density-based layersd
What is clinical significance of ergosterol?
Not found in mammalian cells, so a drug target.
Ergosterol synthesis or in membrane
Lab test method for identifying Candida albicans and Cryptococcus neoformans
Candida albicans = + germ tube test
Cryptococcus neoformans - India stain (negative stain)
Lab methods to diagnose cryptococcal meningitis (as well as therapeutic monitoring)
Culture of spinal fluid or sputum. India ink, latex bead agglutination, CSF titer decreases w/ effective therapy. Fontana Masson stain (melanin)
How does morphology of Blastomyces dermatitidis and HIstoplasma capsulatum differ as they appear in host and environment?
In general, dimorphic are moulds @ 28-30C and yeast @ 37 (except coccidiodes = spherules)
Polyenes MOA, Resistance, Example
ON SUMMATIVE!!!
Bind ergosterol, disrupting membrane
Ergosterol downregulation/ replacement/ reorientation
AmB IV, Nystatin oral/topical
Azoles MOA, Example
ON SUMMATIVE!!!
Inhibit C. P450 demethylation of ianosterol (ergo synth)
Imidazoles (ketoconazole) and triazoles (IVF, itra/vori/flu)
Echinocandins MOA, Resistance, Example
Noncompetitively inhibit B1,3-glucan synthase (cell wall)
Target mod/downreg
-fungins (capso/mica/anidula)
Use for candidiasis
Allyamines MOA, Resistance, Example
Inhibit squalene epoxidase (ergo synth, squalene accumulation)
Target mod/upregulation, penetration
-fines (nafti/terbina[oral])…H-PHOBIC
Used in dermatophytosis
5-fluorocysteine MOA, Resistance
Nucleic acid synth
Rapid resistance
Limited spectrum of activity
What are yeasts? How do yeasts reproduce?
Unicellular and round
mitosis: budding or fission
What are moulds? How do moulds reproduce?
Multicellular and filamentous, hyphae+septa
Use spores + conidia
What’s are the 2 main forms of fungi? What is an example of an alternative form?
Yeasts, Moulds
Spherules: Coccidiodes
Manifestations of Candidiasis and Ecology
Mostly Candida albicans. Yeast infection, thrush, but can infect all organs.
Found in most people in GI/GU tracts. Birth canal, dentures, Abx, immunosuppression, pregnancy
Is Candidiasis contagious? Who gets Candidiasis?
Not usually though it can be found in environment. Typically etiology is from individuals flora.
Patients with neutropenia, diminished phagocytosis, diminished cell mediated immunity (mucocutaneous involvement)
PSEUDOPHYPHAE
String of pearls in retina
What is a mucocutaneous area? What might it indicate?
Where mucus becomes skin (lips, nostril, conjunctiva, vagin, urethra, anus)…candidiasis there indicative of cell-mediated immunity aka CD4 defect.
Kneejerk reaction: PIGEON Droppings Organisms Diseases Also, EUCALYPTUS Diagnosis
CRYPTOCOCCOSIS!!! C. neoformans/gattii/grubbii with HUGE galactoxylomannan capsule (negative immunomodulator, negative stain)
Pneumonia (may evade xray)
Meningitis (esp. in collagen disease patients)
Not dimorphic
Eucalyptus - gattii, immuno-competent peeps
CrAg from CSF
Histoplasmosis
Intracellular (HISTiOcytes!), Tornado Alley area, often in AIDS patients. Pigeon, Bird/bat droppings. Mimics TB.
Treatment: liposomal amphotericin B, Itraconazole
Fistula
Urine ag test
Coin lesion
Blastomycosis
Wider, norther Tornado alley. Mimic TB w/ SKIN+bone lesions. Yeast has broad base bud. DOGS and BEAVER DAM (wet wood). Hyphae pair-shaped
Coccidioidomycosis
SW USA and below. C. immitis/posadasii. Filipinos. Filament in environment. Coccidiodin skin test. Desert bumps/rheumatism.
Treat with triazoles then amphotericin B
Meningitis: lifelong fluconazole
Aspergillosis
Worldwide Organ transplants, burns, foreign bodies Angioinvasive hyphae V shaped branches Diagnose w/ Galactomannan or Beta-D-glucan Only mold, forms moving fungus ball ABPA mimics asthma
Uncontrolled Diabestes
Mucor and Rhizopus
Hyphae at right angles
