Yeast Flashcards
Midterm
it is the main factor why yeasts have been prevalent
immunosuppression
infections caused by yeasts may be — and —
extremely aggressive and difficult to treat
t or f: yeast is often part of the human microbiota
true
yeasts can be classified into
yeast (mostly asexually but able reproduce sexually) and yeast-like (not capable of sexual reproduction)
generally, yeasts can reproduce asexually through —, but they can also reproduce sexually through —
asexually= blastoconidia (budding); sexually= ascopores and basidiospores
give the general characteristics of yeast
eukaryotic, unicellular, round-oval, 2-60um, reproduce asexually (blastoconidia)
what are the characteristics for differentiation of yeasts
cell size, presence and absence of capsule, budding phase (broad, narrow)
diiferentiation of yeast in — and — is ften impossible
direct microscopy and histopathologic examination
an outpouching of the cell wall that becomes tubular and does not have a constriction at its base
germ tube
it represents the initial stage of true hyphae formation
germ tube
buds elongate, fail to dissociate, and form subsequent buds
pseudohyphae
resemble links of sausage
pseudohypahe
have cell wall constrictions rather than true intracellular septation delineating the fungal cell borders
pseudohyphae
macroscopic appearance of yeasts
- moist
- creamy
- may have brght pigments
- either hyaline/melanized (phaeiod)
t or f: some yeasts may produce a capsule resulting in a shiny or mucoid colonial appearance
true
this is responsible for most commonly encountered opportunistic fungal infection
candida spp
candida spp is the — most common cause of hospital acquired bloodstream infection (BSI)
4th most common
mortality rate of candida spp
as high as 50%
this is the most commonly isolated yeast
Candida albicans which causes candidiasis
what are the symptoms/clinical manifestations of candidiasis
oroesophageal candidiasis, intertriginous candidiasis, paronychia, onychomycosis, vulvovaginitis, thrush
what specific clinical manifestation of candidiasis: skin folds are involved
intertriginous candidiasis
what specific clinical manifestation of candidiasis: involves tissues surrounding the nails
paronychia
what specific clinical manifestation of candidiasis: affects nail and nail beds
onychomycosis
what specific clinical manifestation of candidiasis: fish eye
vulvovaginitis
what specific clinical manifestation of candidiasis: an infection of the mucous membranes in the mouth, and is considered a localized infection
thrush
what specific clinical manifestation of candidiasis: can be seen in newborns, patients with HIV, and diabetes
thrush
thrush is infection of candida albicans in what areas
mouth
t or f: thrush caused by candida albicans is a localized infection
true
thrush can be seen in what patients
newborns, HIV, diabetes
enumerate the non-albicans candida
C. glabrata and C. parapsilosis
these are once believed to not cause diseases
non-albicans candida
t or f: non-albicans candida was once believed to not cause disease
true
it is a common urinary isolate candida
C. glabrata
C. glabrata can be differentiated with C. albicans through
sugar (trehalose) assimilation
this candida is resistant to antifungal drugs
C. glabrata
infections caused by C. glabrata can cause
endocarditis and meningitis
C. glabrata is higher in what population
higher in older adults than in young adults and children
this candida is seen in neonates
C. parapsilosis
this candida is the 2nd most common cause of positive blood culture
C. parapsilosis
what candida is positive for germ tube
C. albicans
laboratory diagnosis of Candida
Microscopic appearance and testing for germ tube (only albicans is +)
t or f: in microscopic appearance of candida reveals budding cells
true
diameter of candida in microscopy
2-4um
in microscopic appearance of candida — shows regular points of constrictions
pseudohyphae
what candida demonstrates true septate hyphae
C. albicans
this candida have a smaller blastoconidia at 1-4um
C. glabrata
t or f: yeasts are hard to treat because they are hard to distinguish from each other
true
how to do germ tube
add yeast colony to 0.5mL serum
possible samples for yeast determination
- vaginal discharge
- urine
- sputum
- stool
- wound discharges (oberved through gram stain)
- blood culture
what part of the body is vulvovaginitis be observed
vaginal canal up to cervix (causes bad odor)
thrush is very evident in what part of the body
tongue
this is one of the diagnostic testing done to do to differentiate yeasts
temperature
this causes meningitis, pulmonary disease, and septicemia
cryptococcus spp
these are the most common routine tests done to identify yeasts
germ tube and india ink
it is the major cause of opportunisitc infections in people with AIDS
cryptococcus
cryptococcus is commonly found in
soil contaminated with pigeon droppings
cryptococcus most common specimen
CSF (most routine for india ink testing)
cryptococcus can be acquired through
inhalation
this is the mst notable pathogen of the cryptococcus spp
C. neoformans
this protects the cryptococcus from dry condition
polysaccharide capsules
the main way of identifying C. neoformans using india ink using microscopy
capsulated budding yeast
t or f: cryptococcus loves dry conditions
false, they prefer mucoid/wetter environment
the most widely used and easiest method to test cryptococcus
india ink
this testing method is able to delineate the large capsule of cryptococcus spp due to the inability of the ink to penetrate the capsule
india ink
ratio of sample and india ink
1 drop sample (CSF):1 drop india ink
disadvantage of india ink
less sensitive
this is an immunoassay type of testing for cryptococcus
cryptococcal antigen detection (CAD)
t or f: india ink is more sensitive than cryptococcal antigen detection (CAD)
false, CAD is more sensitive
can be misidentified as positive for india ink
bubbles, WBCs
t or f: clear capsule/halo of capsule indicates bubbles or WBCs
false, clear halo means it is true positive for india ink
t or f: C. neoformans can only have single budding
false, it can have single or multiple budding
shape of C. neoformans
spherical
describe the wall of C. neoformans
thick-walled (due to capsule)
size of C. neoformans
2-15 um in diameter
t or f: polysaccharide capsule is true for all cryptococcus spp
false, it is true to most isolates but not all
this is an opportunistic, atypical fungus
pneumocystis
pneumocystis can be acquired
in early life
t or f: pneumocystis infection is asymptomatic for immunocompetent individuals
true
this yeast is first considered as a protozoan
pneumocystis
fun fact: pneumocystis is classified as yeast instead of protozoan (parasite) after what test
DNA testing
this pneumocystis is previously classified as protozoan and is commonly found in rats
P. carinii
this pneumocystis is often recovered from humans
P. jirovecii
other tests for the identification of yeasts
- carbohydrate assimilation
- chromogenic substrates (CHROMagar)
- cornmeal agar
- potassium nitrate assimilation (KNO3)
- Urease
t or f: EIA can be used for yeast identification
true, but are not readily available, rigorous, and expensive so its not routinely used
this is also called sugar fermentation test
carbohydrate assimilation
this test is used to identify which carbohydrates a yeast can use aerobically as a sole carbon source
carbohydrate assimilation
what are observed or the indications in sugar fermentation (carbohydrate assimilation) test
turbidity, change in color, indicators
this test can be used to differentiate species of candida
chromogenic substrates (CHROMagar cacndida)
this is a differential type of media, especially in candida spp (you can observe the different colonial growth patterns)
CHROMagar candida
this presumptively identifies C albicans, C tropicalis, and about 10 other candida spp
CHROMagar candida
t or f: if you get colonies from CHROMagar, it reveals their true morphologic characteristics microscopically
true
this allows the identification of morphology of yeasts, not just that of candida
cornmeal agar
what morphologies can you observe from colonies of cornmeal agar
- blastoconidia
- chlamydoconidia
- pseudohyphae
- arthroconidia
this determines the ability of yeasts to use nitrates as the sole source of nitrogen
potassium nitrate assimilation (KNO3)
what yeast is the positive control for KNO3
Cryptococcus albidus
what is the negative control for KNO3
Candida albicans
this is used for the detection of isolates producing the enzyme urease through christensen urea agar
urease
what agar is used for urease test
Christensen urea agar
this clinically significant yeast is negative for urease
Candida spp
t or f: most Cryptococcus are negative for urease
false, they are mostly positive
what indicator is observed if urease test is positive
there will be a change in color of the media
