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89 Cards in this Set
- Front
- Back
how many species of fungi are there?
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250,000
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how many species of fungi cause disease?
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180
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what type of organisms are fungi?
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eukaryotes, membrane bound
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what type of genome do they have?
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haploid with introns (around 6000 genes) in nucleus
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what does the membrane contain?
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ergosterols, mannose containing glycoproteins
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what is the cell wall composed of?
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glycan (glucose and mannan), B1,4-linked-N-acetylglucosamine residues, B1,3-linked glucose, glycoproteins
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what may be linked to the glycoproteins?
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asparagine N-linked mannose/galactose, serine/threonine O-linked mannose/galactose residues
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what are dimorphic fungi?
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can exist in either filamentous or yeast
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when are dimorphic fungi filamentous?
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environment under 22C
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when are dimorphic fungi yeasts?
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body over 37C
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what is pseudohyphate?
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short cyclinders by which yeast grows
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how do yeasts mutliply?
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mitosis: symetrical binary fission or asymetrical budding
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what are hypha?
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thin branching multicellular cylinders (filamentous mould),
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how do filamentous moulds mutliple?
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mitosis at tip or branch point
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how are cells held together in a hypha?
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interconnecting cytoplasm or aseptate (common cytoplasm with many nuclei)
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what is a mycelium?
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interwoven mass of hyphae
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what are mushrooms?
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many layers of mycelium
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what are spores?
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small, tough, light fungal cells, adapted for survival in hostile habitats
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what is the asexual state?
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asexual spores produced by mitosis
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what are other names for the asexual state?
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anamorph/mitotic/imperfect state
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what type of spores do yeast in asexual state produce?
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endospores (internal)
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what type of spores do filamentous moulds in asexual state produce?
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exteranal conidia or internal sporagium
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what species can only exist in the asexual state?
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deuteromycota (imperfect fungi)
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what are the other names for the sexual state?
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telpomorph/meiotic/perfect state
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what structures are produced in the sexual state?
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motile gametes or sexual hyphae
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how does sexual reproduction occur?
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gametes/hyphae fuse, reassortment and recombination occur, meiotic reduction division allows two haploid cells to form
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where do sexual spores form?
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ascus (internal tube), abasidium (external structure) or fusion of hyphae
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what are examples of ascomycota species?
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candida (yeast) microsporum (mould) histoplasma (dimorphic)
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what are examples of basidiomycota species?
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cryptoccus (yeast)
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what are examples of zygomycota species?
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mucor (mould)
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what are examples of deuteromycota species?
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coccidioides (dimorphic)
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what reproductive structures do ascomycota make?
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ascus (sexual), conidia (asexual)
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what reproductive structures do basidiomycota make?
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abasidium (sexual),
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what reproductive structures do zygomycota make?
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fusion from hyphae (sexual), sporangium (asexual)
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what reproductive structures do deuteromycota make?
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conidia (asexual)
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how do they get their energy
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preformed organic compounds, extracellular digestion
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where do yeasts live?
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moist environments
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where do filamentous moulds live?
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within their food
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what are saprotrophs?
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feed on dead matter, rarely disease causing
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what are the uses of fungi?
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bread making (CO2), alcohol (ethanol), antibiotics (penecillin), immunosuppressants (cyclosporin)
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what is the immune response to fungi?
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NFKB causes IL6/23/1B -> Th17 (IL17 and 22 to recruit neutrophils) and IL12/TNFa -> Th1 cells (IFNy to activate macrophages)
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what disorders result in a lack of B1-3glycan sensing?
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Dectin-1 deficiency and CARD9 mutations
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what increases suceptibility to candida species?
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IL17 and IL22 autoantibodiess
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what increases suceptibility to deep filamentous mould infections?
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neutropenia (impaired number and function of neutrophils), Chronic granulomatous disease
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what is chronic granulomatus disease?
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mutation in NADPH oxidase system stops the formation of the superoxide that kills fungi in phagosomes
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what predisposes to infections by yeast?
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primary immunodeficiency syndrome (impaired T cell/macrophage function), HIV etc
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what drugs can be used to target ergosterol synthesis?
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azoles (clotrimazole) and allylamines (terbinafine)
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what drugs can be used to target ergosterol function?
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polyenes (amphotericin)
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what drugs can be used to target microtubules?
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griseofulvin
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what drugs can be used to target B1,3-glycan synthesis?
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echinocandins (caspofungin)
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what types of fungal infection may you get?
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food intoxication, commensal infection, superficial, subcutaneous or systemic fungal infections
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what fungal food intoxication?
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rye crops may contain ergotamine toxin causing vasoconstriction
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what fungi is a commensal that can cause infections?
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candida
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what is a superficial fungal infection?
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ring worm, microsporum, candida albicans, pityriasis versicolor
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what is infected in superficial infections?
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dead keratinised skin
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how could you treat tinea ungium (nail) or tinea pedis (feet) infections?
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topical clotrimazole/terbinafine
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how are superficial infecitons aquired?
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spores
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what type of infection do you get with superficial infections?
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chronic, non lifethreatening
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what do mannose rich structures cause?
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activation of complement via MBL
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what does TLR2 recognise?
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phospholipomannan
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what does TLR4 recognise?
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O-linked mannose
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what does Dectin 1 recognise?
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B 1-3 glycan
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what signalling does dectin 1 cause?
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inflammasome and syk/CARD9/MALT1 -> NFkB
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how are subcutaneous fungal infections acquired?
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injury/occupational hazards
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what is sporothrix schenckii?
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rose pickers disease, chronic disease spreads up skin of arm
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what type of fungi can cause asymptomatic infection of macrophaes?
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deep systemic pathogens
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what are systemic pathogens?
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infection is accidental (not needed for life of fungus)
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what is histoplasma capsulatum?
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dimorphic fungus in soil/rat faeces, can live inside macrophages
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what causes the dimorphism of histoplasma capsulatum?
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temperature sensitive DRK1 and RYP1 kinases
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how can histoplasma capsulatum avoid the immune system?
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a-1-3 glycan isn't recognised by PRR, hsp60 binds to CD11 and CD18 on macrophages, CBP (calcium bind protein) faciliates growth in macrophages
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what are the types of histoplasma capsulatum infection?
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asymptomatic (95%), acute pulmonary (flu like), chronic pulmonary (fibrosis), dissemination (spreads - fatal)
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what are systemic oppurtunists?
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severity relates to underlying host infection
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what helps some strains of candida albicans have increases adhesion and invasion?
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pseudohyphae (since yeast in body)
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what is the toxin secreted by candida albicans important in virulence?
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candidalysin (damages epithelial cells)
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what other feature of candida albicans makes it problematic?
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biofilm formation in extracellular matrix
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how can you treat candia infections?
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fluconazole/caspofungin
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what are the types of candida infection?
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oral candidasis, vulvo vaginitis, UTI, oesophagitis, candideamia (IV cannula), disseminated (spread to eyes, liver, heart valves)
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what is pneumocystis jirovecii?
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obligate parasite in humans - lost amino acid sysntheis capacity (yeast)
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how many people are infected with pneumocystis jirovecii?
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almost everyone within 3 years (asymptomatic)
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what disease does pneumocystis jirovecii cause in immunosuppressed people who reacquire a strain?
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lung disease (10% have mutliple strains), pneumocystitis pneumonia
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how do you treat pneumocystis pneumonia?
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high dose co-trimoxazole to inhibit folic acid synthesis and corticosteroids to reduce inflammation
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what is cryptococceus neoformans?
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yeats with thick polysaccharide capsule, abundant in bird droppings
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what types of infection can you get from cryptococceus neuformans?
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pneumonia, meningo-encephalitis (when T-cell suppressed or HIV positive - 20% fatality)
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how do you treat meningo-encephalitis?
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amphotericin and flucytosine and long term fluconazole
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what is aspergillus fumigatus?
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environmental mould with airborn spores, in compost
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what types of infection can you get from aspergillus fumigatus?
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airway colonisation (asthma), aspergilloma (localised mass of hyphae), invasive infection (eg following chemotherapy)
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how would you treat aspergillus fumigatus?
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amphotericin or voriconazole and surgery
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what is Mucor?
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environmental mould with airborn spores, causing fatal mucormycosis
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how would you treat mucor?
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IV amphotericin
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