Spirochetes thin walled , flexible, s.

Medfools Fungus Chart for the USMLE I
Fungus Notes for USMLE I with the usual cheesy mnemonics.
SUPERFICIAL MYCOSES Spherical yeasts, branched Hyphae
Malassezia furfur
Diseases
Tinea versicolor- chronic superficial skin infection w/ hypo or
Branched hyphae, spherical yeasts in KOH
Selenium sulfide shampoo, imidazoles
hyperpigmented areas. Asymptomatic lesions identified by pigment
changes/failure to tan. More frequent in hot/humid weather
Exophiala werneckii
Tinea nigra- chronic superficial infection, black lesions on palms and
Branched hyphae, spherical yeasts in KOH
Selenium sulfide shampoo, imidazoles
CUTANEOUS MYCOSES No Yeast / Branched Hyphae, micro/macroconidia
Dermatophytoses: Microsporum spp., Trichophyton spp., Epidermophyton floccosum
Diseases
Puritic papules, vesicles, Hypersensitivity to fungal
Keratinase- results
Branched hyphae in KOH
Topical imidazoles. Tinea
antigens may present as “dermatophytid” rxns (NOT an
structures, skin,
oral griseofulvin (hair/nail
Chronic infection esp. w/ heat/humidity.
hair, nails.
Wood’s light for some
Tinea corporis- ringworm – body
Microsporum
Tiniea cruris – jock itch- groin
Spread by direct
Tinea pedis- athlete’s foot- toes
contact.
Tinea capitis- head
Tinea unguium- onychomycosis- nails
Tinea barbae- beard
SUBCUTANEOUS MYCOSES Round/Cigar budding yeast/ Branched hyphae w/ oval conidia at tip of conidiophores
Sporothrix schenckii (gardener’s disease)
Diseases
Causes local pustule/ulcer with nodules
Round or cigar shaped budding yeasts in tissue or 37’ Branching
Potassium Iodide
along draining lymphatics (think linear
splinters) Gardeners at risk.
hyphae w/ oval conidia at tip of conidiophores at 25’. (like a daisy—
Introduced by trauma
Think of aGardener planting daisies smoking a cigar!)
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SYTEMIC MYCOSES: general rules
ALL dimorphic, YEASTS in humans (molds in dirt), Human infection by SPORE inhalation, so NO Person-Person transmission (remember yeasts DO
NOT make spores), most infections asymptomatic or mild pneumonia. Dissemination results when IMMUNOCOMPROMISED. Grows as MOLD (mycelia
w/ spores) at 25’C in Sabouraud’s agar and as a YEAST at 37’C in blood agar. Diagnosis by serology or biopsy/culture w/ silver stain. DTH tests useful to
RULE OUT diagnoses. Systemic mycoses need the BIG GUNS: amphotericin B or itraconazole
SYSTEMIC MYCOSES Dimorphic Fungi
Coccidioides immitis (SW USA, Latin America)
Diseases
Coccidiomycosis- mild lung infection, usually
Endemic in arid
Arthrospores are inhaled.
Skin tests w/
asymptomatic or mild pneumonia. Dissemination parts of SW USA,
coccidiodin or
leads to bone granulomas or meningitis.
arthrospores
Latin America.
Arthrospores make spherules w/
spherulin
10% develop erythema nodosum (red tender
doubly refractive wall filled with
nodules on extensor surfaces, indicated DTH rxn to
endospores. On rupture, endospores
fungal antigens – NO organisms in lesions) and
arthragias- “valley fever”, “desert rheumatism”
“Spherules” in
Histoplasma capsulatum (Ohio and Mississippi river valleys)
Histoplasmosis- asymptomatic infrection or mild
Inhaled microconidia develop into
ID budding
pneumonia, disseminated in immunocompromised endemic to Ohio,
yeasts within macrophages.
yeasts WITHIN
Mississippi river
(Histoplasma Hides in macrophages)
macrophages.
valleys. (Think
macroconidia,
OHIstOplama)
Spreads quickly, calcified
microconidia
Bird/bat droppings
granulomas.
w/ histoplasmin
Blastomyces dermatitidis (East of Mississippi, Central America)
Blastomycosis- ALMOST ALWAYS
Round yeast
East of Missisippi,
Inhaled conidia
SYMPTOMATIC! (IT BLASTS YOU!) -
w/ doubly
and Central
disseminates w/ fever, night sweats, weight loss,
refractive wall
America.
skin and lung granulomas
(like coccidio) ,
single broad
Soil, rotton wood.
based bud
Paracoccidiodes brasiliensis (rural Latin America)
Asymptomatic lung lesions, mild pneumonia
Thick walled
Latin America
Spores inhaled
yeast, multiple
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OPPORTUNISTIC MYCOSES All Monomorphic
Candida albicans (yeast only)
Diseases
Vulvovaginitis- vaginal itching/discharge, favored
Oval yeast w/ single
Normal flora of
C.albicans
by high pH, diabetes, antibiotics, oral contraceptives, bud. Can appear as
“pseudohyphae”
other Candida by germ
Cutaneous candidiasis- skin invasion favored by
tubes in serum at 37’C
warmth, moisture: inframammary folds, groin and chlamydospores.
Oral thrush- white exudate in immunocompromised
Esophogeal candidiasis- AIDS defining illness w/
Disseminated candidiasis- Immunocompromised
cellular immunity.
and IVDA
Cryptococcus neoformans (yeast only)
Usually asymptomatic, can cause pneumonia,
Oval budding yeast
Soil w/ pigeon
CSF culture,
bone/skin granulomas. Dissemination causes crap. (Think:
cryptococcal antigen
cryptococcal meningitis, subacute.
polysaccardide
cryptoCOCCUS=
test, India Ink stain
capsule (India ink
pigeon CACA)
Aspergillus fumigatus (mold only)
Invasive necrotizing pneumonia in AIDS, Molds
Septate hyphae, V-
Transmission
Amphotericin B
shapted branches.
by airborne
aspergilloma (FUNGUS BALL), requiring surgery.
Conidia form
Can also induce allergic bronchopulmonary
radiating chains.
aspergillosis, type I hypersensitivity rxn like
abraded skin,
wounds, burns,
A.flavus- grows on cereal or nuts produces
aflatoxins (toxic, carcinogenic to liver)
Mucor/Rhizopus (mold only)
Rhinocerebral mucormycosis- associated w/
Nonseptate hyphae
diabetes, caused by infection of nasal mucosa with w/ broad irregular
invasion of sinuses/orbit. Molds proliferate in walls walls and right
of blood vessels.
angle branches
(compare w/
(Think MUCOR/Rhizopus invades MUCOSA)
aspergillus)
Endospores inside of
sporangium
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Blastomyce
Histoplasm
trichosis
Fungus Morphologies Chart
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shaped sept
of conidiop
isies”)

Source: http://www.medfools.com/downloads/fungus.pdf