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51 Cards in this Set

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  • Back
two important opportunistic pathogen in AIDs
C neoformans and P. carinii
C. neoformins can exist subclinically in AIDs pts in
urinary and respiratory tracts
"AIDS-defining"illness is due to what organism
C. neoformins
the only pathogenic fungus with a capsule
cryptococcus neoformins
the major enviromental sources of Cryptococcus neoformins is
soil and pigeon droppings or eucalyptus trees and decaying wood forming hollows in living trees
C. neoformins grows as what on agar media
yeast (also grows this way in clinical specimans)
gram stain of C. neoformins?
no - stains poorly with gm stain and usual histological stains - need special one
major virulence factor for C. neoformins
polysaccharide glucocuronoxylomannan (GXM) capsule
how many serotypes for c. neoformins
4 (based on capsule)
gatii
variant of C. neoformins with serotypes B and C based on capsule differences
grubii
variant of C. neoformins associated with A serotype

note: serotype has to do w/ carbohydrates in capsuel
C. neoformins serotype D is associated with what variant
neoformans
the most important diagnostic antigen of c. neoformins is
the capsule - with highly synthesis regulation

(polysaccharide glucocuronosylomannan)
melanin is an important virulence factor in what organism
C. neoformins
how does C. neoformins generate melanin which is an important virulence factor
has phenol exidases which use dopamine as a substrate to generate melanin

so many substrates in CNS - helps with trophism?
C. neoformins grows at what temp?
urease?
37 degrees
urease positive
most common disease of C. neoformins
chronic meningitis
route of transmission for C. neo
inhalation of spores or dessicated yeast forms
onset of c. neo is
slow insidious - causes primarily meningitidis
what are two common disseminated sites of C. neoformins
skin and bone
eye lesions and blindess are sequelae of what infection
c. neoformins
C. neo capsule stains what color with mucicarmine
red
treatment for c. neo
amphotericin B plus flucytosine
vaccine for c.neoformins
not yets - in progress - capsular vaccine
fourth most comomon cause of hostpital bloodstream infections
hematogenously disseminated disease caused by candida albicans

oportunistic!
are blood cultures a good way to diagnose C. neoformins
positive blood cultures indicate infection but cultures may be neg even w/ infection
treatment for disseminated C. albicans
Amphotericin B for internal infections
Azoles for internal and mucosal infections
resistance to azoles by c. neoformins is by what two mechanisms
1. mutation of target enzymes
2. increased expression of efflux pumps
is aspergillus dimporphic?
no
aspergillus

only grow in mold (mycelial) form - (aerial hyphae which are septate and have conidiophores bearing brushlike conidiospores which are easilty airborn
in clutures aspergillus grow how
aearial hyphae - septate and have characteristic stalk like conidiophores bearing brush-like conidiospores which are easily airborne

aspergillus is NOT dimorphic
allergic bronchopulmonary reactions to fungal antigens occur leading to respiratory distress in severe cases
this is called and caused by
called hypersensitivity penumonitis caused by aspergillus
explain secondary colonization re aspergillus
pre-existing cavitary lesions in the lungs are colonized by aspergillus which fills up the space with spherical mass of intertwined, branching, septate hyphal elements .
symptom of aspergillus secondary colonization
minimal but if anything - couphing up blood
an important risk factor for systemic aspergillosis
neutropenia
where do you find aspergillus
ubiquitous in enviroment - notably in hospital air

air conditioner filters
aspergillus - normal flora
no - transient colonization may occur
what would you look for in a biopsy of tissue in someone contaminated with aspergillus
septate hyphae that branch at regular intervals and tend to be oriented in the same direction
acute angle branching is another descriptive term for hypha growth in tissue
what would you culture if you suspected aspergillus
bronchial washes, tissue or sputum,
treatment of aspergillus
amphotericin B
zygomycetes, dimorphic?
no - only grow in mycelial (mold) form
unlike aspergillus however the hyphae are not septate
increased suseptibility to zygomycetes occurs w/
metabolic acididosis causing rhinocerebral infections
specific antibodies to this organism are present in all children by age of four and disease is only minifested w/ loss of CMI (AIDS)
pneumocystis carinii (jiroveci)
sf of p. carinii means
each type of animial has its own special form (sf) that does not infect other species
why cant p.carinii not be cultured and grown in animals
(major point)
due to sf (special forms)
four easons p. carinii was originally thought to be a animal parasite
1. morphology
2. susceptibility to antiparasitic agents
3. lack of susceptibility to Amphotericin B
4. Absence of ergosterol and presence of cholesteral and other sterols
four reasons that p. carinii IS classified as a fungus
1. rDNA - fungal taxonomy
2. translation elongation factor 3 (EF3) only found in fungi
3. thymidlylate synthase and dihydrofolate reductase on two separate genes
4. presence of cell wall chitin, glucan, and mannoprotein
cysts (5-8 m)- which contain sporozoites that are released when cyst ruptures
pneumocystis carinii exists as
sporozoites which are released from the p. carinii cyst mature into
pleomorphic trophozoite forms
infections by this organism cause impaired oxygen uptake and asphyxiation
p. carinii
what is the histological hallmark of p. carinii
interstitail pneumonitis with plasma cell infiltrates - alveoli have distinctive foamy appearance
spread of p. carinii
airborne from person to person - highly infectious