Bacteriology: Mycology Flashcards
What is the cell membrane and cell wall of fungus made of?
Cell membrane has ergosterol rather than cholesterol
Cell wall made of chitin
What characteristic of chitin makes it easy to infect animals?
It is difficult to digest but it cannot make their own energy
What is yeast?
unicellular form of a fungus
What is hyphae?
filamentous form of fungus
What are pseudohyphae?
chains of yeast that look like hyphae
What is mold?
a fungus that grows as a mass of hyphae (mycelium)
What are dermatophyte?
fungal organism that causes ringworm
What are endospores?
spore contained within a sac
What are dimorphic fungus?
fungi that exist as yeast forms in animal tissues & as hyphae in environment due to temperature differences.
What are the 3 main ways that fungi grow?
1) budding yeast
2) germinating spore/conidia
3) fruiting body
What are the characteristics of budding yeast?
broad-based
narrow-based
asexual reproduction by budding
the type of budding allows us to differentiate between different oranisms
What are the characteristics of germinating spore/conidia?
forms germ tube that can grow into a new organism
What are the characteristics of fruiting body?
produce many conidia that are each very tiny & light & can be dispersed through the environment
How can fungi spread?
locally by the release of conidia
aerosolized by the release of conidia into the air
What gives rise to the patchy appearance of mold?
The local and aerosolized spread of conidia
What are the 2 types of hyphae?
Septate & nonseptate
What are the characteristics of septate hyphae?
They have lines (septum) that divide the hyphae into “sections”
What are the characteristics of nonseptate hyphae?
There are no lines that divide the hyphae into section
What types of conidia do Dermatophytes have
Arthroconidia and macroconidia and microconidia
What are arthroconidia?
observation in patients
spores release during hyphal fragmentation
What are macroconidia?
observed in lab
big
allows for differentiation between dermatophyte species
What types of growth and reproduction do other fungi species have?
Fruiting bodies, clusters, small little buds
What are the factors that affect the development of fungal disease?
Virulence factors
Tissue affected
Host immunity
Geographic location
Environment
How do we diagnose fungal infections?
Presumptive
Direct swab/observation
Culture
Antibody detection
Antigen detection
What is the best diagnostic technique for superficial skin samples?
wet mount cytology
What is the mounting fluid solution used for wet mount cytologies?
10% potassium hydroxide which clears cellular debris
New methylene blue
lactophenol cotton blue
What types of stain do we use for routine fungal samples?
Diff-quick
Wright-Giemsa
H&E
What types of stain do we use for special fungal samples?
Gamori’s methenamine silver: fungal wall takes up silver in the stain and appear black
Periodic acid-schiff (PAS)
What techniques can we use in direct exam/observation?
Wet mount cytology
Stain/Reaction
Cytology
Impression smear
Histopathology
What is the biggest draw back with fungal cultures?
They can take way to long and this can be dangerous with sever infections. Normal fungal culture can take 4 weeks or more
What samples can we collect to send OUT and which is the best?
Fresh tissue/ fluid–BEST
Swabs– only when you cannot get a better sample
What sort of transport conditions are necessary for samples to be sent OUT?
Overnight shipping to lab
dermatophytes: hair/nails/scales/ skin in a sterile container @ room temp
Room temperature samples if fungal disease is primary differential
send chilled on ice if bacterial contamination or differential
What are the test that can be done IN-HOUSE?
DTM: dermatophyte test media
RSM: rapid sporulation media
What are the characteristics/ draw backs of DTM?
has a pH indicator in media
starts yellow but changes to red/pink with growth of dermatophytes
false positives can occur if you wait to long to read results
Why does the DTM media change color?
pH change occurs when organism eats protein in agar resulting in an ammonia by product, increasing the pH, allowing the agar to change color
What are the infectious species of dermatophytes?
Mycosporum spp
Trichophyton spp.
What disease does dermatophytes cause?
Ringworm
What are the clinical signs of dermatophtophytosis?
Hair loss
Scales
Crusts
Red skin
Pruritis
Papules/pupstules
How can you diagnose Dermatophytosis?
Woods lamp
Cytology (wet or dry))
What liquid is used typically used for a wet mount dermatophyte cytology?
Potassium hydroxide
What makes DTM turn red?
It has phenol red indicator in it
How long does it take for a DTM to become positive?
3-7 days
What causes false positive readings with DTMs?
age– not reading it in the correct time frame
What type of mycoses does dermatophytes cause?
cutaneous mycoses
What type of mycoses does sporotrichosis cause
cutaneous mycoses that can become systemic
What is the dimorphic fungus that is a sporotrichosis?
Sporothrix schenckii
What type of fungus is Sporothrix schenckii
dimorphic fungus
Where does Sporothrix schenckii like to live?
soil, dead vegetation, and roses
What is the typical host of Sporothrix schenckii?
Cats
What must a patient have in order to become infected with sporotrichosis?
and abrasion or puncture/wound
How are sporotrichosis diagnosed and what does it look like?
Usually diagnosed through histopathology and there will be macrophages with ovid yeast in them
What type of mycoses does blastomyces dermatitidis, histoplasma, cryptococcus, and coccidiodes cause?
respiratory mycoses that becomes systemic
What are the characteristics of Blastomyces dermatitidis?
Yeast stain big and blue with broad based budding and are found in wet environments like river valleys
What are the characteristics of Histoplasma?
Many yeast inside of macrophages and are a associated with bat dropping and can be found in the midwest
What are the characteristics of cryptococcus?
Yeast have a big thick capsule and are found all throughout the U.S
What are the characteristics of coccidioides?
Endospores and are found in the southwestern U.S.
What is the pathogenesis of dermatitidis, histoplasma, cryptococcus, and coccidiodes?
Starts with inhalation of the spore & goes to the lungs
then from the lung it is picked up and taken to the lymph system
from there the spore can then invade the host cells if they normally do that
then the phagocytic cells then carry it around through the lymph & blood to other sites
What are the common sites of systemic infection?
Bone & Brain
Eyes
Lymphnodes & lungs
Skin
