Medical Mycology Flashcards by Amanda Romeu

Encapsulated yeast

crypotoccus neoformans

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saprophytes

feed on living and dead organic matter

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Yeast

cultured at 37oC
unicellular
reproduces asexually by budding -> blastoconida
reproduce sexually -> Basidiospore
may contain a capsule - use india ink to ID
ALL are aerobic
grow at wide range of temps, best is room temp

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Filamentous (mold)

vegetative growth of filamentous (filaments packed tightly)
aerobic filamentous fungi
reproduction by spores or conidia
also known as Hyphae

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Mycelium

mass of hyphae

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Transmission of Fungi

most are opportunistic
many switch to hyphal form as invade host
most are not communicable except dermatophytes
enter via respiratory route, mucous membrane and the skin

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sabouraud’s agar

contains pentons, good for dermatophytes

pH is 5.6 to inhibit growth of bacteria

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Blood agar

usually with antibiotics to prevent cross contamination

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Microscopy

skin scrapings with 10% KOH

Light microscopy

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superifical mycoses

confined to stratum corneum (dead keratin layer of skin) or distal portions of hair
mostly cosmetic in nature
no cellular response from host
no pathological changes are elicited

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Dermatophytes

invade keratinized structures
may cause secondary bac. infections and mild inflammation response
Dx- branched hyphae on KOH wet mount, culture ….

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Dermatophyte infections caused by

Microsporum
Epidermophyton
Trichophyton

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sporothrix schenckii

SubQ 
mainly in tropics but seen in US 
found on soil and decaying vegetation 
switches to yeast in human host otherwise Hyphae in soil 
at risk: gardners and landscapers

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Rose-gardner’s disease

causes sportrichosis
nodules at infection site and along draining lymph nodes
full recovery with tx but takes a while
can be disseminated in IC pts

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Candida albicans

subQ 
likes wet, moist regions 
infects nail beds 
Common nosocomial pathogen
Spread by sexual contact

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Malassezia Furfur

causes Pityriasis versicolor
branched hyphae and spores - spaghetti and meatballs
Lipid dep. yeast -> infects young adults with oily skin = Lipophilic
never penetrates skin, only cosmetic
Sun fungus - see easily on darker skin

Furfur treatment

Selenium sulfide shampoo

White Piedra

caused by - Tinea blanca or Trichosporon beigelii
nodules on hair
soft,pale
on hair in groin or axilla

Black Piedra

caused by Piedra hortae

small dark nodules seen on hair shaft

Systemic Mycoses

infected pts dont transmit the disease - non communicable
Large inoculum is required
Inhale the spores -> gives rise to yeast (usually lower lobes), see budding
can overcome the Cell mediated immunity

Histoplasma capsulatum

found ohio-mississippi river valley
Loves nitrogen in soil
found in bat,bird droppings

Just visited a chicken coop or went spelunking in the ohio-mississippi river valley area, what could you have just been exposed to?

Histoplasma capsulatum

See single budding yeast inside Macs with KOH and Parker Ink

Histoplasma Capsulatum

Narrow base budding yeast - thin walled

detect H antigen in Pt

Histoplasma capsulatum

Primary Histoplasmosis

granuloma in lung "summer flu" in Midwest affect the spleen, liver and BM and forms granuloma - very rare - IC pts asymptomatic in 95% cases may resemble TB pneumonia -> Chronic progressive lung disease

Ocular Histoplasmosis

Risk of infection from eye surgery "Histo spots" loss of central vision travel from lungs to eyes and lodge in choroid

Blastomyces dermatitidis

East of mississippi, central america in soil, rotten wood and humid areas round yeast with double refractive wall

Detect Exo-A-Ag

Blastomyces dermatitidis

Blastomycosis

"chicago disease" fever, night sweats, wt loss Granuloma in lungs and skin which may ulcerate can affect skin, pelvis, cranial bones and ribs

Coccidiodes Immitis

most endemic SW US - San Joaquin valley fever Likes sand most virulent of systemic mycoses

Sperules

c. immitis contains lots of endospore most infectious than Histo or Blasto

Fungal Meningitis in IC pts

Cryptococcus Neoformans

Dx of Crytococcus Neoformans

CSF culture look for cryptococcal antigens old method - India Ink stain to detect the capsule

Budding yeast with capsule

Cryptococcus

Pathogenesis of Cryptococcus Neoformans

Inhalation - colonizes lungs - Lung injury loves Brain tissue and meninges cryptococomas -> meningioencephalitis

Cryptococomas

Granuloma in CNS Fever, loss of vision, stiff neck, sometimes vomitting change in mental status