MYCO - characteristics of fungi in direct examination, STAINS, TESTING Flashcards
small, oval to round budding cells, often found in ‘clustered in histiocytes’, difficult to detect when present in small numbers
histoplasma capsulatum
small oval to round ‘cigar shaped’, single or multiple buds present; uncommonly seen in clinical specimens
sporothrix spp
cells exhibit great variation in size; usually spherical but may be ‘football shaped’, buds single or multiple and ‘pinched off’, capsule may or may not be evident ocassionally, pseudohyphal forms with or without a capsule may be seen in exudates of cerebrospinal fluid
cryptococcus spp
small, ‘bottle-shaped cells,’ buds separated from parent cells by a septum, emerge from a small collar
malassezia furfur
cells are usually large, ‘double refractile’ when present, buds usually single, however, several may remain attached to parent cells, buds connected by a broad base
blastomycoses spp
cells ae usually large and are surrounded by similar buds around the periphery “‘mariners’ wheel appearance’”
buds have pinched off appearance as well
paracoccidioides brasiliensis
fungi that has a morphology of ‘yeast like’
histoplasma capsulatum
sporothrix spp
cryptococcus spp
malassezia furfur
blastomyces spp
paraccocidioides brasiliensis
fungi that has a morphology of ‘spherules’
coccidioides spp
rhinosporidium seeberi
cells usually exhibit single budding; pseudohyphae when present, are constricted at the ends and remain attached like links of sausage, when hyphae are present it’s septate
candida albicans except glabrata
short, curved hyphal elements are usually present
along with round yeast cells that retain their spherical shape in compacted clusters
‘spaghetti and meatballs ‘
malassezia furfur
hyphae are large, ribbonlike, often fractured or twisted, occasional septa may be present, similar hyphae are confused with aspergillus spp, particularly A.flavus
Pauciseptate hyphae - mucorales mucor, rhizopus and other genera
hyphae, septate are commonly seen; chains of arthroconidia may be present
dematophytes - skin and nails
arthroconidia on periphery of hair shaft producing a sheath indicate ectothrix infection;
arthroconidia formed by fragmentation of hyphae in the hair shaft indicate endothrix infection
dermatophytes, hair
hyphae are septate and exhibit dichotomous, 45 degree branching
larger hyphae
often disturbed, may resemble those of mucorales
aspergillus
hyphae and rectangular arthroconidia are present and sometimes rounded irregular forms may be present
geotrichum spp
hyphae and rectangular arthroconidia are present and sometimes rounded
occasionally, blastoconidia may be present
trichosporon spp
traditionally, KOH is the recommended when it comes to direct examination, but nowadays, ____ is believed to be superior
calcofluor white stain
Currently no commercially available procedures exist for
serologic testing of most fungi. However, serology testing may be a useful tool with select organisms, such as
Cryptococcus,
Blastomyces,
Histoplasma, and
Aspergillus spp.
Antibody testing has proven useful, but not for immunocompromised
patients, who are incapable of producing
a measurable humoral response.
true or false
true
is a sensitive method that is
difficult to perform and interpret. It requires a delay in testing
that extends from exposure to the onset of symptoms; consequently,
detection of antibody can take 2 to 3 months
complement fixation
is a simple, cost-effective procedure.
Although it is 100% specific, it is relatively insensitive
and is not used as a screening tool. This test also requires
2 to 3 weeks to exhibit a positive result.
immunodiffusion
is a biophysical
method that significantly reduces the time
required to specifically identify fungal organisms
Matrix-Assisted Laser Desorption Ionization
Mass Spectrometry
Most often yeasts are identified through the use of a combination
of tests
Identification factors and techniques
include the following:
- Colonial morphologic features
- Microscopic morphologic features
- Physiologic studies
- Rapid commercial yeast identification tests
__ stain is useful when Cryptococcus organisms
are suspected
India ink
