Flashcards in Medical Mycology Deck (74)
What are the characteristics of fungus?
contain a nucleus
contain membrane bound organelles
-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?
What is the structure of the fungus?
Cell wall - antigenic, multilayered
- Polysaccharides (chitin, chitosan, cellulos, glucan, mannan)
- bilayered made of phospholipids and sterols (ergosterol, zymosterol)
-protects the cytoplasm and facilitates capsules and cell wall synthesis
-nucleolus, ER, mitochondria
Polysaccharide Capsule -*****Cryptococcus neoformans**
What is the encapsulated yeast we are supposed to know?
What is thermal dimorphism?
Two different forms based on temperature
Yeast (at 37 degrees)
- 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
-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).
Distinguish between pseudohyphae, non-septate, and septate?
Pseudohyphae (lack cytoplasmic connections between cells)
What does pathogenesis depend on?
structure of fungus
What will a fungal infection cause?
How are fungal infections transmitted?
Most are not communicable (except dermatophytes)
What agars are used to identify fungus?
What do the antifungal drugs work on?
Ergosterol synthesis (makes up cell membrane)
-amphotericin B (lots of side effects)
What are 4 types of fungal infections?
What subcutaneous infection do we need to know?
What does superficial mycoses affect?
epidermis at the stratum corneum layer
- normally no pathological change
How is dermatophyte diagnosed?
Branched hyphae on KOH wet mount
-culture - myobiotic sugar
-Sabourand's dextrose sugar
All dermatophyte infections are caused by members of what 3 genera?
What is tinea corparis?
ringworm (trunk, arms, legs)
What is tinea cruris?
jock itch (groin)
What is tinea pedis
ringworm of scalp
ringworm of hand
What is white piedra caused by?
What is black piedra caused by ?
What treatments are available topically? oral?
topical (miconazole, clorthrimazole)
oral (Griseofulin, Ketaconazole)
What is the name of the organism that causes pityriasis versicolor?
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?
What does Sporothrix schenckii cause?
Rose Gardener's disease
What can candida albicans cause orally?
What fungus can be transmitted person to person?
How are systemic fungal infections transmitted?
-will give rise to yeast in body- single cell and budding
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?
Clinical symptoms of Histoplasma capsulatum may resemble what disease?
Where is Blastomyces dermatitidis geographically located?
East of Mississippi River Valley
Where is Blastomyces dermatitidis found in nature?
soil, rotten wood
Describe the structure of Blastomyces dermatitidis ,
Round yeast with double refractive wall and single broad based budding
What does Blastomyces dermatitidis cause?
cough up blood
Which fungus is the most endemic?
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
What population would be susceptible to Cryptococcus neoformans?
Where is Cryptococcus neoformans found?
associated with soil contaminated with pigeon droppings
Which fungal organism causes meningitis?
How would you confirm Cryptococcus neoformans?
Which organism stains with India ink?
Cryptococcus neoformans (encapsulated)
How is Cryptococcus neoformans transmitted?
inhalation>> colonizes the lung>>lung injury
What disease can result from Candida?
endocarditis (IV drug users)
What pH does Candida require?
Which bacteria can maintain the pH so that Candida cannot grow?
When is esophageal candidiasis seen?
What population does Disseminated candidiasis affect?
IV drug users
Where is Aspergillus funigatus found?
In the body and environment Aspergillus funigatus exists in what form?
acute angle hyphae form with septae
(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
Where does Aspergillus funigatus colonize?
preformed cavities and debilitated tissues
Zygomycosis is associated with what 3 species?
Zygomycosis is seed in what population?
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