Yeast Flashcards
What is Candida
where is it found
Candidiasis (an infection with Candida sp)
Candidemia: presence of Candida in the blood
-NF in oral, skin GI tract , endogenous
-opportunistic
-Albicans is most common
-yeast infection
C. auris (nosocomial infections)
C. tropicalis (nosocomial infections)
C. parapsilosis (*nosocomial infections)
What are the 3 types of infection that Candda forms
Mucocutaneous
Oral, vaginal, trachea, bronchi, GI tract
Cutaneous
most caused by C.albicans
Can invade skin and nails
Systemic
Rare
Immunosuppressive disease
how do we ID Candida albicans
-Germ tube production
-get pseudohyphae
-Chlamydospore production on oxgall bile or cornmeal agar
-Difficult to differentiate from C. dubliniensis
-Growth at 42○C -one on SAB OR BA and compare growth temps
-India Ink & urea: negative
What is Candida dubliniensis
where is it found
-found in urine, stool , vagina and oral cavity -NF
-associated with oral carriage
-opportunistic
-repeated infections caused by lower sensitivity to anti fungals
-resistance to fluconazole can be developed with repeated use
how do we ID Candida dubliniensis
Difficult to differentiate from C. albicans **
-albicans has one lollipop spore at the end where as dubliniensis has spores that clusters and chain
-Germ tube production
-Chlamydospore production on oxgall bile or cornmeal agar
-NO Growth at 42○C
-Identification from most commercial systems, MALDI
-India Ink & urea: negative
What is candida auris
-new pathogen
-need to identify in case there is resistance to common anti fungals
-can be misidentified
-can be transmissible
-causes candidiasis in immuno comp patients
-samples from blood, sputum , bile , wound)
-get a full ID
What does candida auris look like in lab
-multidrug resistant
-germ tube negative NO chlamydospores
-Urea and India Ink negative (no capsules produced) THIS GIVES YOU CANDIDA SPP NOT ALBICANS
-test on maldi if updated or PCR
*If urea pos, set up India Ink to look for Cryptococcus
**If chlamydospore has hyphae, that is characteristic of Candida species and you so not need to rule out Cryptococcus, regardless of the urea result
What is cryptococcus neoformans
-bird droppings
-systemic infections in immuno comps
-Route of entry is inhalation, pulmonary often asymptomatic
-causes CNS (chronic meningitis) especially in AIDS patients
-Yeast-like, with capsule, budding cells but no pseudohyphae or true hyphae
-Presumptive identification based on colonial recognition: Colonies mucoid because of a capsule
how to ID crypto in the lab
Urea positive ***
Germ Tube negative
Does not produce chlamydospores
No pseudohyphae
No growth on media with cycloheximide
No growth at 42°C
india ink positive = HALO
more grey than white
What is the Rhodotorula species
-Bright salmon pink coral red, yellow
-Mucoid (encapsulated)
-No pseudohyphae
-Urea positive
-Opportunistic - AIDS, acute leukemia
-Meningitis, endocarditis, via central venous catheter infections
What do you see as Macroscopic Observations Sabouraud (SAB)
-Colony 3-5 mm, raised, entire or round, “buttery”
-When you take a colony and put it in saline on your slide –it usually disperses (or starts to disperse) before it is even mixed
-white, cream
-Rhodotorula pinks
-Crypto – may be darker (more tan than cream) in colour and may have a capsule
-SAB selects for or selects out specific yeast
What do you see as Microscopic Observation for yeast
-Wet Preparation from the colony – quickly distinguishes yeast from bacterial colonies
-turn down iris diaphragm to increase contrast for light field but for dark field open the iris
-Stains Gram positive dont call them GP
-Round to oval budding yeast cells (NOT cocci)
-Report as “yeast”
-With/without pseudohyphae “links of sausage” has constrictions at base (this tells you its pseudo)
What is Budding & Pseudohyphae
-asexual reproduction called budding
-bud is the blastoconidium which stays attached to the mother cell because stain deposits can look like yeast
-candida is polymorphic can exist in many form
What is pseudohyphae and why is it called that?
What: Continued budding resulting in a long chain of blastoconidia called pseudohyphae
Why: They lack the cellular cross-walls associated with TRUE hyphae
what is corn meal agar- used like oxgall looking for chlamydospore production
What is the germ tube
-Filamentous extension from a yeast cell
-true” germ tube lacks constriction at the bases, where they attach to the mother cell.
-Constriction at the base = pseudo germ tubes
Provides a presumptive identification.
-Non sterile site: GT + = presumptive as C. albicans.
-Sterile site: GT +, identification must be confirmed because C. dubliniensis is also GT +
-GT negative – not C. albicans
Touch colony and inoculate plasma; 2-3 hrs, 35-37
how is Chlamydospore Production (Dalmau Technique) done
-on oxgall agar inoculate surface by scratching the surface
-coverslip
-incubate
-read
