MIDTERM LEC 1: AGENTS OF YEAST Flashcards
2 classifications of yeast fungi
Yeast
Yeast like fungi
Isolates that reproduce sexually,
Yeast
Not capable of sexual reproduction or whose sexual state has not been discovered
Yeast like fungi
How do yeast reproduce sexually
By forming ascospores or basidiospores
Most common recognized yeast pathogens
Candida spp.
Species most commonly isolated from clinical material
Candida albicans
Where are Candida spp. naturally found as normal flora
GI tract
Mucous membranes
Skin
Common risk factors of developing Candidiasis
1) Diabetes
2) Immunosuppressive disease or therapy
3) Neutropenia
4) AIDS
5) High dose chemotherapy
Blood stream infections such as fungal endocarditis can be fostered by
Use of indwelling vascular lines
All Candida spp. exist as what kind of form
Oval yeastlike forms
All Candida spp exist as oval yeastlike forms that produce:
Buds or blastoconidia
Candida spp produce hyphae and pseudohyphae except what species
Candida glabrata
C. galbrata consume what sugar
Trehalose
Second most common species of Candida
C. glabrata
Describe the colony of C. galbrata
Smooth, white, creamy, domed colonies
C. albicans and other spp may undergo what process wherein a single strain may change reversibly among several different morphotypes
Phenotypic switching
most frequent infection of candida albicans causes _______ of the skin
erythematous lesion
erythematous lesion is sometimes accompanied by
creamy, white exudate or scaling
common sites of erythematous lesion of the skin
groin
between fingers and toes
under the female breast
axilla
T or F:
workers who immerse their hands in the water for long periods of time are also at risk for infection of the hand skin
T
Candida yeast infection of the nails
onychomycosis
Candida yeast infection of the nail bed
paronychium
clinical manifestation of oral candidiasis
creamy white patches (thrush/cottage-cheese like patches on the mouth) overlying erythematous buccal mucosa
oral candidiasis is aka
moniliasis
thrush is recognized as an indicator of what
indicator of immunosuppression
hallmark of failed immune system
oral thrush
what condition can occur in heavy infection of oral thrush
dysphagia
oral candidiasis is a common initial infection in patients with what disease
HIV
T or F:
Oral candidiasis is a marker of immune failure in HIV px
T
inflammatory condition that affects the commissures of the mouth, causing break in the tissue with redness, crusting, and scaling
angular cheilitis
angular cheilitis is aka
perleche
angular cheilitis is often caused by:
buildup of saliva in the fissures
how can Candida cause angular cheilitis
due to presence of saliva, making the tissue soft allowing the Candida to infect the area (lateral fissure)
occurs as fungal infx on esophagus
esophagitis
T or F:
esophagitis cannot cause dysphagia
F
it can, due to painful lesions
erosive lesions of the distal esophagus and stomach resulting in substernal pain which is aggravated by swallowing
Gastrointestinal candidiasis
T or F:
Gastrointestinal candidiasis occurs more frequently as esophagitis and less commonly as gastritis
T
fungal infx in the vagina
Vulvovaginitis
factors of vulvovaginitis
1) Antibiotic
2) Pregnancy
3) Uncontrolled diabetes
4) Impaired immune system
why does pregnancy considered a risk for having vulvovaginitis
high estrogen= glycogen
why does diabetes put you at risk for having vulvovaginitis
increased glucose
vaginal discharge of vulvovaginitis
cottage cheese
why is Candida urinary tract infection difficult to diagnose
the yeast is frequently recovered from urine as a result of vaginal contamination or colonization of the bladder in px with indwelling catheters
Candida infection of the upper urinary tract
urinary tract infection
infection of the upper urinary tract can include necrosis of what part of the urinary tract
renal papillae
renal papillae necrosis occurs primarily in patients with what condition
obstructive uropathy
type of candidiasis that involve sources other than skin or mucous membranes
invasive candidiasis
isolation of Candida spp from at least one blood culture specimen with hematogenous spread of the yeast to one or more organs
Candidemia
onychomycosis is frequently due to
dermatophytes or non dermatophyte
what dermatophyte cause onychomycosis
Tinea unguium
what non dermatophyte cause onychomycosis
Candidal onychomycosis
clinical manifestation of paronychomycosis
infected area can become swollen, red, and painful, and a pus-filled blister may form
which parts of the body is intertriginous candidiasis commonly seen
axillae
groin
inter and submammary folds
intergluteal folds
interdigital spaces
umbilicus
factors of intertriginous candidiasis
1) moisture
2) heat
3) friction
4) maceration of the skin
diaper rash is aka
candidal diaper dermatitis
steps of invasion process
1) Adhesion
2) Uptake
3) Penetration
virulence factor of yeast that grants the ability to stick to host cells, triggering a switch to hyphal form and growth towards the host
adhesins
virulence factor of yeast that facilitate host cell engulfment of the fungus through stimulated endocytosis
invasins
how is active penetration through host cell barriers enabled
through combination of adhesion, physical force, and fungal enzymes
biofilm formation consists of
yeast cells (below)
hyphae (above)
how can Candida change its surface features and biofilm formation abilities
phenotypic switching
scrapings of mucosal or cutaneous lesions may be examined directly after treatment of what reagent
10-20% KOH containing calcofluor white
tissue specimens, scrapings and swabs from the mouth or vagina should be inoculated unto primary isolation media with or without what reagent
cycloheximide
what does the presence of filamentous extension from the edges of the colony indicate
microscopic indication that a pseudohyhae are being produced
In histological sections, Candida stains poorly with what stain
H&E
In histological sections, Candida stains well with what stains
Periodic Acid Schiff (PAS)
Gomori Methenamine Silver
Gridley fungus
definitive identification of C. albicans when germ test tube appears negative
Cornmeal Tween 80 Agar
what does Cornmeal Twee 80 Agar detect
chlamydoconidia produced by C. albicans
most generally accepted and economical method used to identify yeats
Germ tube test
how many percent of the yeasts recovered from clinical specimens are Candida albicans
80%
how many hours can germ tube test reveal the identification of organism
3 hours
Identify:
(+) germ tube test @ 35 C
C. dubliniensis
Identify:
(+) germ tube test @ 35C & 42C
C. albicans
Identify:
(-) germ tube test
other candida
define germ tube
hyphae-like extensions of young yeast cells showing parallel sides, aseptate and will not constrict at their point of origin
look like germ tubes but are septate constricted at their point of origin
pseudohyphae
what organism produce “pseudo-germ tubes”
C. tropicalis
describe pseudo-germ tubes
constricted at the base or point of germ tube origin
what does C. tropicalis form
blastoconidial germination w/ constriction
most commonly used conventional definitive identification of yeast
Carbohydrate assimilation test
T or F:
Not all Candida spp use glucose in CAT
F
all of them
CAT:
C. albicans
glucose
CAT:
C. krusei
glucose
CAT:
C. dubliniensis
glucose
CAT:
C. tropicalis
maltose, sucrose
CAT:
C. galbrata
trehalose
differential medium useful for the recovery of Candida
Chrom Agar Candida
different enzymes of different Candida spp. react with what substances to yield a characteristic color
chromogenic substances
CAC:
C. albicans
green
CAC:
C. dubliniensis
lighter green compared to C. albicans
CAC:
C. krusei
Pale pink-purplish pink
CAC:
C. galbrata
Creamy white
CAC:
C. tropicalis
Metallic blue; bluish green
treatment for thrush and other mucocutaneous form of candidiasis
topical nystatin or oral ketoconazole or fluconazole
treatment for systemic candidiasis
Amphotericin B
most protective measure in treatment
avoid disturbing the balance of microbiota and intact host defenses
T or F:
Candidiasis is not communicable
T
what organism causes meningitis, pulmonary disease and septicemia
Cryptococcus spp
CD4 count in px with AIDS infected with Cryptococcus
<200
in what environment is Cryptococcus abundantly found
soil, trees, pigeon droppings
Cryptococcus primarily affects which organs
primarily the lungs, then disseminate to the meninges and other sites
Serotypes of Cryptcoccus
A, B, C, D
A and D serotype
C. neoformans var neoformans
B and C serotype
C. neoformans var gattii
T or F:
Cryptococcus is encapsulated
T
how does Cryptococcus replicate
by budding from a relatively narrow base
how many buds are formed by Cryptococcus
usually single, but multiple buds and chains of budding cells are sometimes present
Cryptococcus only produces what kind of spores
blastoconidia
Cryptococcus does not produce true hyphae or pseudohyphae on what agar
cornmeal agar
Cryptococcosis is aka
torulosis/torulepsis
may present as a pneumonic process or more commonly, as CNS infx secondary to hematogenous and lymphatic spread from a primary pulmonary focus
Cryptococcosis
variable in presentation from an asymptomatic process to a more fulminant bilateral pneumonia
pulmonary cryptococcosis
neurotropic Cryptococcus spp
C. neoformans and C. gattii
most common form of dse of C. neoformans and C. gatii
cerebromeningeal
uncommon in C. neoformans but are the most common presentation of CNS cryptococcosis with C. gatii
Cryptococcomas (parenchymal lesions)
other manifestations of disseminated cryptococcosis
1) skin lesions (10-15% of px)
2) ocular infections
3) osseous lesions
4) prostatic involvement
5) asymptomatic reservoir of infection
Cryptococcal meningitis is also referred to as
Busse-Buschke Disease
when was Cryptococcus discovered
1894
major factors contributing to the virulence of Cryptococcus
capsule of the fungus comprises polysaccharides glucuronoxylomannan and glucuronoxylomannogalactan
virulence factor of Cryptococcus that functions as an antioxidant, defending against reactive oxygen species
Melanin
virulence factor of Cryptococcus that contribute to brain edema, advancing to cryptococcal meningitis when elevated un the CNS
Mannitol
what temperature does Cryptococcus grows best for survival in the mammalian host
37C
virulence factor of Cryptococcus that facilitates the degradation of host tissues and evasion of immune responses
secretion of proteases, phospholipases, and urease
adaptation strategy of Cryptococcus that involves the entry into the host via phagocytic cells and later escaping to colonize other tissues
Trojan Horse mechanism
adaptation strategy of Cryptococcus in which it alters capsule size and cell shape under specific conditions; aids in avoiding detection by the host immune system
Phenotypic variation
mode of entry of Cryptococcus
inhalation of spores or yeast cells
Cryptococcus in healthy individuals
mimic influenza-like symptoms (asymptomatic)
Cryptococcus in immunocompromised patients
hematogenous dissemination
specimens for culture for Cryptococcus
blood
CSF
other clinical material
microscopic examination of CSF with Cryptococcus
characteristic encapsulated budding yeast cells
colonies appearance of Cryptococcus in culture
mucoid colonies
stain for Cryptococcus
India ink or nigrosin
stained characteristics of Cryptococcus
unstained halo are seen around individual cells
diagnosis of cryptococcal meningitis
direct detection of capsular polysaccharide antigen in serum or CSF or urine
how is the capsular polysaccharide antigen of Cryptococcus detected in serum, CSF or urine
through latex agglutination or enzyme immunoassay kits
T or F:
all species of Cryptococcus are urease positive and the nitrate reaction rate differs
T
color of Cryptococcus colonies on birdseed agar
brown-black
brown-black color of Cryptococcus colonies is due to what substance
phenol oxidase
phenol oxidase assimilates what subtsance
creatinine
bird seed agar is aka
Niger seed/Staib’s
gram stain appearance of Cryptococcus
classic starburst/sunburst appearance in CSF
Cryptococcus:
urease
positive
Cryptococcus:
nitrate reduction
positive
Cryptococcus:
inositol
positive
Cryptococcus:
cycloheximide
susceptible (sensitive)
C. neoformans is extremely difficult to distinguish from what species
C. gattii
key laboratory characteristic of C. gattii
usage of glycine as a sole carbon and nitrogen source in the presence of canavanine
