Exam 2 Flashcards
3 major approaches to the diagnosis of mycotic diseases
clinical settings - patient symptoms
tissue laboratory - pathology; biopsy
microbiologist & hematology
specimen types
blood, bronchoscopy, CSF, exudates, hair, skin, nails, prostatic secretions, sputum, tissue biopsies, urine SWABS ARE NOT ACCEPTABLE
KOH prep
w/ or w/o calcofluor white added will clear the background of cellular and protein material used for skin & sputum specimens
Lactophenol Aniline Blue
most common stain for scotch tape & tease mount preparations from fungal cultures may also be used to visualize yeast and FUNGAL STRUCTURES in clinical specimens
Sabouraud’s dextrose agar advantages
non-selective medium most commonly used, all molds will grow
lower dextrose & high pH = enhances fungal sporation!
Sabouraud’s dextrose agar disadvantages
contaminants will also grow; not recommended for dimorphic fungi
Cornmeal agar advantages
supports the growth of yeats and some fungal pathogens used for yeast
Cornmeal agar disadvantages
supports fungal & bacterial contaminants
Brain Heart Infusion with antibiotics advantages
prevent overgrowth of bacterial & fungal contaminants used for dimorphic fungi
Brain Heart Infusion with antibiotics disadvantages
inhibits Nocardia asteriodes, inhibits some strains of cryptococcus neoformans, inhibits yeast phase of dimorphic fungi
Storage of fungal specimens
NEVER FROZEN
Temperature for incubation of cultures
25-30*C
minimum time for discarding cultures
30 day minimum
Aerial
the portion of the mycelium growing above the surface medium from which fruiting bodies and sporulation commonly occurs
Aleuriospore
a spore or conidium that is attached laterally or terminally to the hyphae or conidiophore via a specialized cell that fragments or fractures upon detachment
Aseptate
a mycelium & hyphae that are not separated by a transverse septations & through which the endoplasm flows freely
Blastoconidia
a spore or conidium that detaches at a predetermined point of budding
Chlamydospore
a reproductive unit derived from a pre-existent hyphal cell, most commonly seen in cornmeal mounts of Candida Albucans. they may form at the apex (terminal), the side (sessile) or within (intercalary) the hypha
Columella
A terminal extension of the sporangiophore of Zygomyces species, projecting into the fertile area of a sporangium
Conidium
A term derived from the latin word ‘dust’, referring to the reproductive spores produced from the tips or sides of specialized fruiting bodies known as phialides
conidiophore
a specialized hyphal extension that supports the fruiting head from which conidia are produced
Dematiaceous
a term derived from the lain ‘ dark’, in reference to the black melanin-like pigment that is produced by many fungal species, imparting a black pigment to the colony
Dimorphic
a term that describes those fungal species, often pathogens, that grow in the mold form at environmental temperatures (25C), but as a yeast when incubated at 35C
Endospore
a spore that is produced from specialized conidiogenous cells that line a secondary structure, such as the spherules seen in coccidioides immitis, photo
Hyaline
mycelium or hyphae that are non-pigmented and appear clear when viewed by transmitted light
Hypha
fundamental unit of a fungus; the tubular strand or filament that comprises the vegetative mycelium
Myceliume
the composite mat or thallus of fungal growth, made up of individual intertwining hyphae
Nodal
the derivation of the sporangiophores immediately adjacent to the root-like rhizoids
Rhizoid
root-like structures produced from the hyphae of certain species of Zygomyces that serve no particular function
Rugae
the folds & creases that often form on the surface of many filamentous molds
Septum
the transverse structure of a hypha that serves to separate individual cells
Philalide
the immediate cells from which conidia are produced, they do not increase in length during conidiation, in contrast to annellides
Vegetative
portion of a thallus or mycelium that grows beneath the surface of the substrate, in contrast to the aerial hyphae that extend airborne over the top of the medium
3 medically important genera of the Zygomycetes & the structural characteristics that separate them
- Rhizopus- nodal rhizoids @ base, hyphae are not divided, white fluffly mold w/ black dots
- Mucor- doesn’t have any rhizoids/root-like structures
- Cunninghamella- no roots/rhizoids
- Absidia- similar to rhizopus & mucor, has rhizoids inbetween th eend of the stalks (INTERNODAL RHIZOIDS)
- circinella- circullar or curved sporangiophores
3 general microscopic features that are unique to Zygomycetes
aseptate hyphae
sporangium w/ spores inside
most have rhizoids
3 clinical forms of Zygomycosis
Cutaneous
pulmonary
systemic
Aspergillus flavus
macro: yellowish/brown colony; ‘lid-lifters’
micro: spherical vesticle; double row of philalides
A. fumigatus
thermophile: grows up to 45*C
Macro: greenish-gray with white edges
micro: clubbed shaped vesicle, phialides & conidia are only present on the top half of the ves icle
A. niger
macro: pepper color colony
micro: doulbe row of phialides, short rows of black conidia ‘dark afro’
can also cause swimmer’s ear
A. terreus
macro: cinnamon brown in color
micro: dome shaped vesicle with long row of conidia
‘fluffier’ than A. fumigatus
Syndromes associated with pulmonary Aspergillus
- allergic pulmonary disease:
- most likely correlated with A. fumigatus or A. flavus
- branched hyphae in sputum specimen is diagnostic
- eosinophilia in sputum & blood samples
- shark-o-laden crystals
- fungus ball infeciton:
- A. niger or A. fumigatus
- grows a colony in the cavity of the lungs or sinuses
- usually in ICP
how to determine a clinically significant fungus from a contaminant?
culture organism from multiple sites/ multiple specimens
Hyaline molds in general
pastel colored (except for penicillin)
can cause keramytosis, mycetomas, & systemic infections
usually in ICP
Fusarium
rapid growth : 3-5 days
lavender colonies, very pretty
sickle, crescent shaped multi-celled conidia
causes corneal ulcers & mycetomas
Penicillium
rapid growth: 3-5 days
yellowish, green, bluish green colonies
long septate hyphae
causes endocarditis, opthalmia
Scopulariopsis
rapid growth: 2-6 days
powdery buff to brown color with radial grooves
septate hyphae
Scedosporium
looks like little sperm
Gliocladium
white-greenish color ‘green lawn’
flask shaped phialide with a ‘flower’ at the end
3 features that separate hyaline molds from aspergilli
- hyaline molds do not have a vesicle
- hyaline molds have conidia in clusters or single; aspergillus conidia are in chains from the phialides
- hyaline molds can have multi-celled conidia
T-agar
differentiat Trichopyton tonserans (will grow) from veracusum
various agars with various growth requirements ( thiamine & inositol)
Urease test
differentiates between T. mentagrophytes (+) & T. rubrum (-)
Trichophyton general microscopic characteristics
macro conidia - sparse or absent; when present they can be long & pencil shaped
micro conidia are abundant
Microsporum general microscopic characteristics
many macro conidia
can have a variety of appearances
usually have few micro conidia
Epidermophyton general microscopic characteristics
macro conidia are large & club shaped
2-5 cells per macro conidia
usually do not have micro conidia
Microsporum Gypseum
4-7 days to grow
off-white/buff color - can become more brownish after a few days
macro conidia, multi-celled, bumpy wall
attached directly to hyphae
infects animals > humans (skin & scalp)
Microsporum canis
5-10 day growth
white w/ lemony/yellow colored apron
large multicelled macro conidia with pointed ends & terminal knobs; breakaway cell attached to hyphae
infected hair will fluoresce under a lamp - yellowish green
no microconidia
Trichophyton mentagrophytes
6-10 day growth
produced spiral hyphae w/ micro conidia - ‘clusters of grapes’ & macro conidia that are smooth walled & skinny
can infect hair, skin & nails
positive hair bating test & positive urease test & grows on all T agars
Trichophyton rubrum
7-10 days growth
white/cream on top, reverse side is RED
negative for hair bating test & negative/weak urease
sparse microconidia - ‘birds on a fence’
skin & nail infections
Trichophyton tonsurans
10-12 days
suede like colony with folds
‘birds on fence’ micro conidia
hair infection - tinea capitis
Epidermophyton floccosum
7-10 days
khaki colored colony
no micro conidia
skin & nail infections & atheletes foot
