Medical Mycology Flashcards
What are the characteristics of fungus?
eukaryotic contain a nucleus contain membrane bound organelles Heterotrophic -lack chlorophyll (not autotrophic) - saprophytes (feed on living and dead organic matter) or parasitic (utilize living tissue) Thermally dimorphic (mostly) - can exist in different forms based on temperature Kingdom - Mycota
Which agent is associated with Meningitis in the immunocompromised?
Cryptococcus
What is the structure of the fungus?
Cell wall - antigenic, multilayered
- Polysaccharides (chitin, chitosan, cellulos, glucan, mannan)
Cell membrane:
- bilayered made of phospholipids and sterols (ergosterol, zymosterol)
- protects the cytoplasm and facilitates capsules and cell wall synthesis
Cytoplasm:
-nucleolus, ER, mitochondria
Polysaccharide Capsule -***Cryptococcus neoformans
What is the encapsulated yeast we are supposed to know?
Cryptococcus neoformans
- antiphagocytic
- agglutination reaction
What is thermal dimorphism?
Two different forms based on temperature Yeast (at 37 degrees) - unicellular - reproduces asexually by budding - also sexually >>>basidiospore - India ink can be used to identify - all yeasts are aerobic and grows at wide range of temperature
Filamentous (Mold)
- multicellular
- vegetative growth of filamentous
- aerobic filamentous fungi
- mass of hyphae make up “Mycelium”
What is a septae hyphae?
hyphae separated by septum
The spores will become (mold/yeast).
mold
Distinguish between pseudohyphae, non-septate, and septate?
Non-septate (coenocytic)
Septate
Pseudohyphae (lack cytoplasmic connections between cells)
What does pathogenesis depend on?
immune response
structure of fungus
What will a fungal infection cause?
granuloma somewhere
How are fungal infections transmitted?
environment
Most are not communicable (except dermatophytes)
What agars are used to identify fungus?
Sabouraud’s agar
Blood agar
microscopy
What do the antifungal drugs work on?
Ergosterol synthesis (makes up cell membrane)
- allylamines
- azoles
- morpholines
- polyenes
- amphotericin B (lots of side effects)
- nystatin
What are 4 types of fungal infections?
superficial
subcutaneous
systemic
opportunistic
What subcutaneous infection do we need to know?
sporothrix schenckii
What does superficial mycoses affect?
epidermis at the stratum corneum layer
- not invasive
- normally no pathological change
How is dermatophyte diagnosed?
Branched hyphae on KOH wet mount
-culture - myobiotic sugar
-Sabourand’s dextrose sugar
Wood’s light
All dermatophyte infections are caused by members of what 3 genera?
- microsporum
- epidermophyton
- tricophyton
What is tinea corparis?
ringworm (trunk, arms, legs)
What is tinea cruris?
jock itch (groin)
What is tinea pedis
athlete’s foot
tinea capits
ringworm of scalp
Tinea unguium
nail fungus
Tinea manus
ringworm of hand
What is white piedra caused by?
Tinea blanca
Trichosporon beigelii
What is black piedra caused by ?
Piedra hortae
What treatments are available topically? oral?
topical (miconazole, clorthrimazole)
oral (Griseofulin, Ketaconazole)
What is the name of the organism that causes pityriasis versicolor?
Malassezia furfur
How is Malassezia furfur diagnosed?
presence of branched hyphae resembling spaghetti and meatballs
How does the Malassezia furfur yeast appear?
spherical on KOH mount
Who is at risk for Sporothrix schenckii?
golfers, rose gardeners, landscapers
What is the distribution of Sporothrix schenckii?
world wide, mainly in tropical areas
How is Sporothrix schenckii transmitted?
traumatic implantation
What does Sporothrix schenckii cause?
Rose Gardener’s disease
Sportrichosis
What can candida albicans cause orally?
thrush
What fungus can be transmitted person to person?
candida albicans
How are systemic fungal infections transmitted?
inhalation thermally dimorphic -to lung -will give rise to yeast in body- single cell and budding **not communicable
What happens when macrophage encounters yeast?
granuloma will form
chest x-ray will show consolidation
Describe Histoplasma capsulatum’s geographical location.
Geographical distribution (Ohio-Mississippi River valley) loves nitrogen in soil
Where is Histoplasma capsulatum found?
bat, pigeon, and chicken droppings
Who is at risk for Histoplasma capsulatum?
access to chicken coops, spelunking
How would you diagnose Histoplasma capsulatum?
yeast is budding with narrow base***
KOH and Parker Ink
Look for H- Antigen
What will happen in 95% of cases of Histoplasma capsulatum?
nothing
Clinical symptoms of Histoplasma capsulatum may resemble what disease?
TB pneumonia
Where is Blastomyces dermatitidis geographically located?
East of Mississippi River Valley
Central America
Where is Blastomyces dermatitidis found in nature?
soil, rotten wood
beaver dam
Describe the structure of Blastomyces dermatitidis ,
Round yeast with double refractive wall and single broad based budding
What does Blastomyces dermatitidis cause?
Chicago disease
fever
night sweats
cough up blood
Which fungus is the most endemic?
Coccidiodes immitis
Where is Coccidiodes immitis geographically located?
SW United States
San Joaquin valley
Why is Coccidiodes immitis so important?
transmission is via a spherules through inhalation of arthrospore
-sac ruptures and releases
What is the geographic location of Paracoccidiodes
Rural Latin America and some of South America
What has multiple, narrow base budding yeast cells
“steering wheel”?
Paracoccidiodes brasiliensis
What population would be susceptible to Cryptococcus neoformans?
immunocompromised
AIDS patients
Where is Cryptococcus neoformans found?
associated with soil contaminated with pigeon droppings
Which fungal organism causes meningitis?
Cryptococcus neoformans
How would you confirm Cryptococcus neoformans?
lumbar puncture
CSF culture
Which organism stains with India ink?
Cryptococcus neoformans (encapsulated)
How is Cryptococcus neoformans transmitted?
inhalation» colonizes the lung»lung injury
“Cryptococomas”
What disease can result from Candida?
diaper rash
endocarditis (IV drug users)
What pH does Candida require?
pH 7.4
Which bacteria can maintain the pH so that Candida cannot grow?
lacto bacillus
When is esophageal candidiasis seen?
immunodeficiency
What population does Disseminated candidiasis affect?
immunocompromised
IV drug users
Where is Aspergillus funigatus found?
world wide
In the body and environment Aspergillus funigatus exists in what form?
acute angle hyphae form with septae
flowering head
(no head, no thermal dimorphism)
How is Aspergillus funigatus transmitted?
inhalation or traumatic inoculation of conidia
What are the signs and symptoms of Aspergillus funigatus?
release of mycotoxins»»mycotoxicosis
Aflatoxin via corn or nuts
Ergots
Where does Aspergillus funigatus colonize?
preformed cavities and debilitated tissues
Zygomycosis is associated with what 3 species?
Rhizopus
Mucor
Rhizomucor abisdia
Zygomycosis is seed in what population?
immunocompromised
old
diabetic
How would Zygomycosis appear under a microscope?
hyphae with wide branches, no septae
What causes fungal pneumonia?
Pneumocystis jiroveci (AIDS defining illness) CD4 count < 100
What are risk factors for Pneumocystis jiroveci ?
CD4 < 200 cells/uL Prior PCP infection oral thrush recurrent bacterial pneumonia HIV
