Fungal Pathogens - Ii

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two important opportunistic pathogen in AIDs

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C neoformans and P. carinii

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C. neoformins can exist subclinically in AIDs pts in

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urinary and respiratory tracts

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"AIDS-defining"illness is due to what organism

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C. neoformins

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the only pathogenic fungus with a capsule

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cryptococcus neoformins

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the major enviromental sources of Cryptococcus neoformins is

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soil and pigeon droppings or eucalyptus trees and decaying wood forming hollows in living trees

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C. neoformins grows as what on agar media

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yeast (also grows this way in clinical specimans)

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gram stain of C. neoformins?

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no - stains poorly with gm stain and usual histological stains - need special one

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major virulence factor for C. neoformins

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polysaccharide glucocuronoxylomannan (GXM) capsule

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how many serotypes for c. neoformins

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4 (based on capsule)

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gatii

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variant of C. neoformins with serotypes B and C based on capsule differences

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grubii

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variant of C. neoformins associated with A serotype

note: serotype has to do w/ carbohydrates in capsuel

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C. neoformins serotype D is associated with what variant

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neoformans

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the most important diagnostic antigen of c. neoformins is

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the capsule - with highly synthesis regulation

(polysaccharide glucocuronosylomannan)

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melanin is an important virulence factor in what organism

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C. neoformins

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how does C. neoformins generate melanin which is an important virulence factor

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has phenol exidases which use dopamine as a substrate to generate melanin

so many substrates in CNS - helps with trophism?

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C. neoformins grows at what temp?
urease?

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37 degrees
urease positive

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most common disease of C. neoformins

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chronic meningitis

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route of transmission for C. neo

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inhalation of spores or dessicated yeast forms

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onset of c. neo is

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slow insidious - causes primarily meningitidis

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what are two common disseminated sites of C. neoformins

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skin and bone

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eye lesions and blindess are sequelae of what infection

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c. neoformins

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C. neo capsule stains what color with mucicarmine

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red

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treatment for c. neo

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amphotericin B plus flucytosine

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vaccine for c.neoformins

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not yets - in progress - capsular vaccine

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fourth most comomon cause of hostpital bloodstream infections

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hematogenously disseminated disease caused by candida albicans

oportunistic!

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are blood cultures a good way to diagnose C. neoformins

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positive blood cultures indicate infection but cultures may be neg even w/ infection

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treatment for disseminated C. albicans

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Amphotericin B for internal infections
Azoles for internal and mucosal infections

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resistance to azoles by c. neoformins is by what two mechanisms

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1. mutation of target enzymes
2. increased expression of efflux pumps

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is aspergillus dimporphic?

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no
aspergillus

only grow in mold (mycelial) form - (aerial hyphae which are septate and have conidiophores bearing brushlike conidiospores which are easilty airborn

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in clutures aspergillus grow how

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aearial hyphae - septate and have characteristic stalk like conidiophores bearing brush-like conidiospores which are easily airborne

aspergillus is NOT dimorphic

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allergic bronchopulmonary reactions to fungal antigens occur leading to respiratory distress in severe cases
this is called and caused by

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called hypersensitivity penumonitis caused by aspergillus

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explain secondary colonization re aspergillus

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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 .

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symptom of aspergillus secondary colonization

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minimal but if anything - couphing up blood

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an important risk factor for systemic aspergillosis

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neutropenia

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where do you find aspergillus

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ubiquitous in enviroment - notably in hospital air

air conditioner filters

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aspergillus - normal flora

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no - transient colonization may occur

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what would you look for in a biopsy of tissue in someone contaminated with aspergillus

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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

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what would you culture if you suspected aspergillus

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bronchial washes, tissue or sputum,

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treatment of aspergillus

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amphotericin B

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zygomycetes, dimorphic?

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no - only grow in mycelial (mold) form
unlike aspergillus however the hyphae are not septate

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increased suseptibility to zygomycetes occurs w/

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metabolic acididosis causing rhinocerebral infections

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specific antibodies to this organism are present in all children by age of four and disease is only minifested w/ loss of CMI (AIDS)

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pneumocystis carinii (jiroveci)

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sf of p. carinii means

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each type of animial has its own special form (sf) that does not infect other species

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why cant p.carinii not be cultured and grown in animals
(major point)

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due to sf (special forms)

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four easons p. carinii was originally thought to be a animal parasite

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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

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four reasons that p. carinii IS classified as a fungus

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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

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cysts (5-8 m)- which contain sporozoites that are released when cyst ruptures

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pneumocystis carinii exists as

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sporozoites which are released from the p. carinii cyst mature into

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pleomorphic trophozoite forms

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infections by this organism cause impaired oxygen uptake and asphyxiation

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p. carinii

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what is the histological hallmark of p. carinii

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interstitail pneumonitis with plasma cell infiltrates - alveoli have distinctive foamy appearance

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spread of p. carinii

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airborne from person to person - highly infectious