Cryptococcus neoformans and other Yeast Dr Sharon Walmsley University Health Network Toronto.
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Transcript of Cryptococcus neoformans and other Yeast Dr Sharon Walmsley University Health Network Toronto.
Cryptococcus neoformans and other Yeast
Dr Sharon Walmsley
University Health Network
Toronto
Organism
• Encapsulated
• Heterobasidiomycetous fungi
• Asexual stage – simple narrow based budding
• Sexual – bipolar system, in-vitro
• 19 species
Identification
• Routine laboratory media
• 48-72 hours, 30-35ºC
• May be inhibited by cycloheximide
• White/cream opaque colonies which become mucoid with prolonged incubation
Rapid identification
• India ink
• Urease test (ureaammoniapH)
• Laccase activity (diphenolic compoundsmelanin) – niger seed agar
Rapid Urease Test
Histopathology
• Prominent capsule
• Spherical narrow based budding yeast
• May have hyphae or pseudohyphae
• 5-10 mm diameter
• 4 serotypes based on capsule
Ecology
• Saprobe in nature – fruit, trees, rotting wood, soil
• Bird guano – pigeons, turkey, chickens
Epidemiology
• HIV• Lymphoproliferative disroders• Sarcoidosis• Corticosteroids• Hyper IgM or IgE syndrome• Monoclonal antibodies (infliximab)• SLE• CD4 T-cell lymphoma (idiopathic)• Diabetes• Organ transplant• Peritoneal dialysis• Cirrhosis
• 20% without HIV have no underlying comorbidity
Spectrum of Disease
Colonization Asymptomatic Disease
Rates of Disease
Pre-AIDS .8/10 6/ year
1992 5/10 6/year
HAART 1/10 6/year
Africa/HIV 15-45%
Rates in Transplant
• 18/100,000
• Increased with cell mediated immune inhibitors
• Highest in kidney and liver
• Rarely carried in through transplanted organ
Serotypes - Cryptococcus neoformans
• A-D
• Commercially available antibody tests
• Biochemical tests
• PCR
Serotypes - Cryptococcus neoformans
Serotype
A – 80% clinical cases
B – tropical, subtropical – S. California, Hawaii, Brazil, Australia, SE Asia
C – rare
D – Europe – Denmark, Germany, Italy, France, Switzerland
Pathogenesis
• Inhalation
• Traumatic inoculation
• Human – human – contaminated transplant tissue
• Zoonosis?
Pathogenicity
• Capsule – polysaccharide
• Melanin
• High temperature growth (37ºC)
Host Response
• Cellular immune response, granulomatous inflammation
• Th – 1 polarized
• Cytokines – TNF, 1F-8, 1L-2
• Proinflammatory 1L-12, 1L-18, MCP-1, MIP
• NK cells
Pathogenesis
Host defense
Size of Virulence of
Inoculation strain
Clinical Manifestations
Lung- Portal of entry- asymptomatic (1/3) life threatening
pneumonia (ARDS)- Endobronchial colonization underlying
chronic lung disease- Single pulmonary nodule- Symptomatic – acute, subacute
Clinical Manifestations
CNS- Subacute meningitis or meningo-encephalitis- Headache, fever, cranial nerve palsies, lethargy, coma- Subacute (days) monthsHIV- Higher yeast burden incidence raised intracranial pressure- Often disseminated- Immune reconstitution disease
Cryptococcal meningitis
Cryptococcus- Oral Lesions
Clinical Manifestations
Skin
- Papule with ulcerated center
- Cellulitis, abscess
- Rarely underlying bone lesions
Prostrate
- Asymptomatic (sanctuary)
- Penile, vulvar lesions
Cryptococcus, skin lesions
Cryptococcus, skin lesions
Clinical Manifestations
Eye
- Ocular palsy, papilledema, optic neuritis
- Retinal exudates +/- iritis
- endophthalmitis
Diagnosis
Microscopic– India Ink (50-80% + CSF)– Gram– Calcoflur white– Silver stain
Culture– Blood agar– Routine blood culture
Cryptococcus, India Ink
Diagnosis
Serology– Latex agglutination, EIA, 90% sensitive &
specific
Radiology– CXR – infiltrates, nodules, lymphadenopathy,
cavitation, effusion– CT/MRI – 50% normal, hydrocephalus,
nodules
In vitro susceptibility testing
• Low MICs – amphotericin, flucytosine, azole
• High MICs – caspofungin
• In vitro R demonstrated but most refractory cases are relapses
Therapy – Cryptococcal meningitis
• Amphotericin B +/- flucytosine
• Fluconazole
• Amphotercin x 2 wk then fluconazole 400-800 mg/d x 8-10 wk
• Chronic suppression fluconazole 200 mg/d
Raised ICP
• CSF OP > 250mm
• Rapidly progressive cerebral edema
• Repeated LP, shunt
• Corticosteroids not useful
Prognosis
• Need to be able to control underlying disease immunosuppression prednisone– HAART– ? Adjunctive cytokines – interferon, GCSF
Poor prognosis
Burden of organism( + India Ink, crypto Ag > 1:1024, poor CSF
inflammatory response < 20 cells/uL)
Sensorium
Mortality 10-25%
Prevention
• Fluconazole prophylaxis
• Active immunization- cryptococcal GXM-tetanus toxoid conjugate vaccine- in animal models, no human trials
• Monoclonal antibodies- would require repeated injections
• Avoid high risk environments
Cryptococcus neoformans (var gattii)
• Initially described in Australia
• Cultured from vegetation around river red gum trees, eucalyptus trees
• Recent outbreak Vancouver Island
Cryptococcus neoformans var gatti
• Outbreak Vancouver Island, January 02
• N = 59, 2 deaths
Cryptococcus neoformans var gatti
• 75% primarily pulmonary disease
• 25% CNS
• 58% male, 5.3% Asian
• Mean age 60
• Certain geographic locations
• Never cultured from bird guano
• May be associated with certain trees
Cryptococcus neoformans
C ryp to co cu s n eo fo rm a ns
va r g ru b ii
(n o w C .g a tt i)
va r ga tti va r e n o fo rm a ns
C.gattiVancouver Island
• 1999-2003– 8.5 – 37/10⁶/year
• Australia - endemic– 94 cases/million/year
C.gatti
• Usually restricted to tropical, subtropical
• Now in temperate zone
• Able to identify an environmental reservoir
• Identified in sea animals
Cryptococcus
• Global epidemiology• Study – Canada 1984• N = 78• 7.7% C.gatti• 79.5% C.neoformans v grubii• 6.4% C.neoformans v neoformans (serotype D)• 6.4% C.neoformans v neoformans (hybid AD)