Medical Mycology Flashcards
Encapsulated yeast
crypotoccus neoformans
saprophytes
feed on living and dead organic matter
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
Filamentous (mold)
vegetative growth of filamentous (filaments packed tightly)
aerobic filamentous fungi
reproduction by spores or conidia
also known as Hyphae
Mycelium
mass of hyphae
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
sabouraud’s agar
contains pentons, good for dermatophytes
pH is 5.6 to inhibit growth of bacteria
Blood agar
usually with antibiotics to prevent cross contamination
Microscopy
skin scrapings with 10% KOH
Light microscopy
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
Dermatophytes
invade keratinized structures
may cause secondary bac. infections and mild inflammation response
Dx- branched hyphae on KOH wet mount, culture ….
Dermatophyte infections caused by
Microsporum
Epidermophyton
Trichophyton
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
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
Candida albicans
subQ likes wet, moist regions infects nail beds Common nosocomial pathogen Spread by sexual contact
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
