Fungi Flashcards
What is the unicellular growth form of fungi? how do they reproduce?
yeast- budding
What is it called when yeast cell buds do not separate
pseudohyphae
What are hyphae
threadlike branching, cylindrical tubules of fungal cells attached end by end
What are molds
mycelia
multicellular colonies of clumped hyphae
produce spores
what are dimorphic fungi
fungi that grow as either yeast or mold depending on environment and temperature
What are Saprophytes
fungi that live in and utilize organic matter as energy source
Describe the innermost layer of fungi
cell membrane that is bilayer and has lots of sterols- ergosterol
How do most antifungals work
disrupting ergosterol
like amphotericin B and nystatin
or ergosterol syntehsis- azoles
What component of fungi are strong Ag to human immune system
the Cell wall
What stain do you use to visualize the capsule of fungi
India ink stain
What are the superficial fungal infections
pityriasis versicolor and tinea nigra
what is presentation of pityriasis versicolor
hypo and hyper pigmented patches on the skin
caused by Malassezia furfur
What is the presentation of tinea nigra
causes dark brown black painless patches on soles of hands and feet
caused by exophiala werneckii
How do you Dx tinea nigra or pityriasis versicolor
skins crapings mied with KOH will reveal hyphae and spherical yeast
What is the best Tx for superficial fungal diseases
dandruff shampoo that has selenium sulfate
what fungi cause cutaneous fungal infections
dermatophytes
What enzyme do dermatophytes secrete
keratinase
What are the most common dermatophytes
Microsporum, Trichophyton and Epidermophyton
presentation of tinea corporis
ring with red raised border
areas of active inflammation and area of healing in middle
ring worm
What is tinea cruris
jock itch
itchy red patches on groin and scrotum
what is tinea pedis
athletes foot
cracking and peeling of skin between toes
what is tinea capitis
scaly red lesions with loss of hair on scalp
what is tinea unguium
thickened nails that are discolored and brittle
onychomycosis
What do you use to Dx microsporum
direct examination of hair and skin with Woods light
will fluoresce green
What does candida albicans cause
oral thrush, diaper rash and vaginitis
how do subcut fungal infections gain entrance
trauma to the skin
What causes sporptichosis
sporothrix schenckii
Presentation of sporothrichosis
subcut nodule that becomes necrotic and ulcerates
follows lymph tracts
yeast at 37 C
hyphae at 25C
What is quick cheap Tx for sporothrichosis
Potassium iodide
What is chromoblastomycosis? what cause it
subcut infection caused by variety of copper-colored soil saprophytes found on rotting wood
Phialophora and Cladosporium
Presentation of chromoblastomycosis
small violet wartlike lesion that over mo-yrs many arise nearby, look like cauliflower
How do you Dx chromoblastomycosis
KOH reveal copper-colored sclerotic bodies
What fungi cause systemic disease in humans
Histoplasma capsulatum, Blastomyces dermatidis, Coccidioides immitis
Describe characteristics of the fungi that cause systemic disease
dimorphic
mycelial forms with spores at 25 C
yeast form at 37 C
Where are Histoplasma and Bastomyces endemics
Mississippi River area
Where is Coccidioides endemic
Arizona and old southwestern areas
AIDS patient with opportunistic infection that previously lived in Arizona. most likley Dx?
Coccidioides
What are the 3 clinical presentations of the systemic fungi
asymptomatic
pneumonia- like TB
disseminated- rare
What is the best way to Dx systemic fungi
biopsy of affected tissue
silver stain
NOT PPD type because many people have been exposed
What is different of systemic fungal infections vs TB
not person to person transmission
fungi have spores, not acid fast
What is Histoplasma capsulatum assoc with
exposure to bat and bird droppings
cleaning chiken coops or spelunking
What is presentation of Blastomyces dermatitidis
weight loss, night sweats, lung involvement and skin ulcers
What type of fungi is Cryptococcus
polysaccharide encapsulated yeast, not dimorphic
What is the major manifestation of cryptococcus infection
meningoencephalitis
Where is cryptococcus neoformans found? what population does it infect?
pigeon poop
AIDS paitents- 10%
What is the risk of cryptococcal meningitis without Tx
death from cerebral edema and brainstem compression
What is the Dx for cryptococcus infection
lumbar puncture and CSF analysis
What does the India ink stain of cryptococcus look like
halo of polyscarrachride capsule around yeast cells
What is the most sensitive/confirmatory cryptococcal lab
cryptococcal Ag test
What are the 3 cutaneous infections caused by Candida
oral thrush- creamy white exudate
Vaginitis- cottage cheese
diaper rash- red and macerated
What can candida cause in immunocompromised host
esophagitis- burning substernal pain worse with swallowing
disseminated- every organ
see white fluffy candidal patches in retina
What is the clinical pearl of candida detection in samples
normal in urine, stool and sputum
abnormal in blood!!!! immunocompromised
What 3 types of diseases are caused by Aspergillus
Allergic Bronchopulmonary Aspergillosis (ABPA)
infection in preformed lung cavities “Aspergilloma”
invasive infection of lung “invasive aspergillosis”
What type of reaction is ABPA
type 1 HS reaction IgE mediated with bronchospasm
blood eosinphilia
also type 4 DTH with cell mediated inflammation and lung infiltrates
What is an aspergilloma
lung cavitations from TB or malignancies that grow aspergillus fungal ball in cavity
What is Tx for aspergilloma
surgical excision
What is presentation of invasive aspergillosus
slowly progressive asymptomatic pneumonia, multiple nodular infiltrates
high mortality rate
What toxin does aspergillus secrete? where is it most prominent?
Aflatoxin
peanuts grains and rice in sahara desert in Africa
What patients are at highest risk for mucormycosis infection
profound acidotic patients like diabetics, immunocompromised, burn patients or those taking iron chelator deferox-amine
What areas do the mucormycosis fungi infect
sinuses, cranial bones and blood vessels
What are the fungi like bacteria
Actinomycetes and Nocardia
What is important about Actinomycetes
gram + filamentous beaded anaerobe normal flora eroding abscesses sulfur granules treat with Penicillin
What is important about Nocardia
gram + beaded filamentous ACID FAST
not normal flora
misDx as TB alot
Tx with sulfamethoxazole
