MYCO & VIROLOGY L4 (Midterms- Yeast) Flashcards
Yeast :P
Incidence of Yeast infection has escalated due to the increasing?
Immunosuppression among patients
TRUE OR FALSE: Cutaneous infections may be extremely aggressive and difficult to treat
**FALSE. Should be Yeast infection
Coined term for those not capable of sexual reproduction
Yeast-like
Able to reproduce sexually
Yeast
Often part of microbiota
Agents Yeast Infection
Generally, yeast reproduce asexually which is through the ____________ but they can also reproduce sexually through ___________
blastoconidia; ascospores and basidiospores
Enumerate at least three general characteristics of a Yeast
- Eukaryotic
- Unicellular organism
- Round to oval
- Size: 2-60 um
- Reproduce asexually by budding (blastoconidia)
Enumerate the characteristics for differentiation of yeasts
- Cell size
- Presence and absence of capsule
- Budding base (broad, narrow)
TRUE OR FALSE: Differentiation of yeasts in direct microscopic and histopathologic examination of clinical specimen is often impossible.
TRUE
An outpouching of the cell wall that becomes tubular and does not have a constriction at its base
Germ Tube
Buds elongate, fail to dissociate, and form subsequent buds; resemble links of sausage
Pseudohyphae
Have cell wall constrictions rather than true intracellular septation delineating the fungal cell border
Pseudohyphae
It represents the initial stage of true hyphae formation
Germ Tube
Macroscopically, it appears moist, creamy, may have bright pigments, and is either hyaline/melanized
Yeasts
Yeasts may produce a capsule resulting in a ______ or ________ colonial appearance
shiny; mucoid
Responsible for the most commonly encountered opportunistic fungal infections
Candida spp.
Fourth most common cause of hospital acquired bloodstream infections (BSI)
Candida spp.
Mortality rate of Candida spp. is as high as?
50%
The most commonly isolated yeast
C. albicans
An infection of the mucous membranes in the mouth, is considered a localized infection
Thrush (caused by Candida spp.)
Thrush can be seen in?
newborns and patients with HIV
These are once believed to not cause a disease
Non-Albicans Candida
Common urinary isolate, resistant to antifungal drugs, infections include endocarditis and meningitis, and is higher in older adults than in young adults and children
C. glabrata
C. glabrata can be differentiated from C. albicans through?
sugar (trehalose) assimilation
Seen in neonates and the second common cause of positive blood culture
C. parapsilosis
This organism is positive (+) for Germ tube
C. albicans
Microscopically, it reveals budding yeast cells, 2-4 um in diamater
Non-Albicans Candida
This shows regular points of constrictions
Pseudohyphae
This candida spp. has true septate hyphae
C. albicans
Which candida has a smaller blastoconidia at 1-4 um?
C. glabrata
Cause meningitis, pulmonary disease and septicemia. Major cause of opportunistic infections w/ AIDS
Cryptococcus spp.
Causes paronychia, onychomycosis, vulvovaginitis (fish-eye), and thrush
Candida spp.
Commonly found in soil contaminated with pigeon droppings
Cryptococcus spp.
Cryptococcus spp. is acquired through?
inhalation
Most notable pathogen of the Cryptococcus spp.
C. neoformans
Exhibit polysaccharide capsules that protect it from dry conditions
Cryptococcus spp.
Most common sample for Cryptococcus spp.
CSF
Less sensitive and is able to delineates the large capsule due to the inability of the ink to penetrate the capsule
India Ink
Most widely used method in testing for Cryptococcus spp.
India Ink
Aside from India ink, what is the other test utilized to test for Cryptococcus spp.
Cryptococcal Antigen Detection (CAD)
Opportunistic, atypical fungus and acquired in early life
Pneumocystis
Microscopically, it appears as spherical, single or multiple-budding. Thick walled, 2-15 um diameter, and has a polysaccharide capsule
C. neoformans
Asymptomatic in immunocompetent individuals.
Pneumocystis
First considered as protozoan (parasite)
Pneumocystis
What are the two agents of Pneumocystis?
P. carinii & P. jirovecii
Previously classified as protozoa and is commonly founds in rats
P.carinii
Often recovered from humans
P.jirovecii
Sugar fermentation test (turbidity, change in color). This identifies which carbohydrates a yeast can use aerobically as a sole carbon source.
Carbohydrate Assimilation
Presumptively identify C.albicans, C.tropicalis, and about 10 other species
Chromogenic Substrates (CHROMagar Candida)
Identification using CHROMagar, is based on different colony colors, depending on the breakdown of ____________ by the different species
chromogenic substrates
Differential media; morphologic characteristic is possible
Chromogenic Substrates
Allows identification of morphology of yeasts such as:
- Blastoconidia
- Chlamydoconidia
- Pseudohyphae
- Arthroconidia
Cornmeal Agar
The characteristic budding yeast forms usually seen on direct mounts of yeasts.
Blastoconidia
These are produced when the blastoconidia germinate to form a filamentous mat
Pseudohyphae
The ________ help determine whether the structures are true hyphae or pseudohyphae
cross-walls
Its cross-walls are constricted and not true septations
Pseudohyphae
________ remain parallel at cross- walls, with no indentation
True hyphae
Begin as true hyphae but break apart at the cross walls with maturity
Arthroconidia
Determine the ability of yeasts to use nitrate as the sole source of nitrogen
Potassium Nitrate Assimilation (KNO3)
This organism is the +Control in Potassium Nitrate Assimilation (KNO3)
Cryptococcus albidus
This organism is the -Control in Potassium Nitrate Assimilation (KNO3)
C. albicans
Detection of isolates producing the enzyme urease is through?
Christensen urea agar
In this test, clinically significant Candida spp. are negative, while most Cryptococcus are positive
Urease
Produces chlamydoconidia along with hyphae
C. albicans
Causes candidiasis in which skin folds are involved
Intertriginous candidiasis
Affects tissues surrounding the nails
Paronychia
Affects nails and nail beds
Onchomycosis
Causes fish eye
Vulvovaginitis
