Opportunistic Mycoses Part 2 Flashcards
(basidiomycetous yeasts) cause £meningitis, pulmonary disease, and septicemia* after inhalation of desiccated yeast cells or possibly the smaller basidiospores.
Possess large polysaccharide capsules.
Cryptococcus spp.
: worldwide in nature, isolated readily from dry pigeon feces, trees, & soil, etc.
• C neoformans species complex
: associated with trees (i.e. eucalyptus) in tropical areas.
Emerging pathogens.
Pacific Northwest of the United States & Canada.
C. gattii species complex (C gattii, C. bacilisporus, C deuterogattii, C tetragattii, & C decagattil)
-rom pigeon guano to the brain
Crytococcus
From the lungs, these neurotropic yeasts typically migrate to the central nervous system where they cause meningoencephalitis.
They also have the capacity to infect many other organs.
Syndrome: fever, fatigue, dry cough, headache, blurred vision, confusion
Cryptococcosis
: Prevalent among people with
HIVIAIDS. Estimated 152,000 cases of cryptococcal meningitis each year; & estimated 112,000 deaths occur, majority in sub-Saharan Africa.
: associated with normal hosts,
13%-33% death rates (cdc.gov)
C. neoformans
C. gatii
MOT of Cryptococcus
Inhalation of desiccated yeast/ basidiospore to pulmonary alveoli
Cryptococcosis
CML
CAPSULE
MELANIN
LACCASE
Cryptococcosis
Virulence Factors
1.______
inhibit phagocytosis and promote survival in the body; glucuronoxylomannan (GXM)
& galactoxylomannan (GalXM) = GXMGal
2._____ - dark pigment embedded in the cell wall; protects the cellular proteins from oxidation and nitrogen radicals (phenyl oxidase)
- ______- believed to oxidize brain catecholamines & iron as a defense against host immune cells
Capsule
Melanin
Laccase
Cryptococcus
Novel virulence factor: “_______” - helps establish infection in the lungs;
giant cells evade immune cells;
protect smaller cells to increase the fungal burden in hosts.
TITAN CELLS
Typical yeast cells is about _____.
In the lungs, Titan cells are_______ in diameter.
Features include altered cell wall structure, compacted capsules, and resistance to antimicrobial stress.
5um
50 to 100 um
Crytococcus
Direct microscopy - wet mounts directly and after mixing with______ (delineates the capsule);_____,_____,_____,_____
India ink
nigrosin, mucicarmine stain, Masson-Fontana, Alcian blue
Cryptococcus
Culture, 37°C, colonies after a few days.
Media with_____ INHIBIT Cryptococcus and should be avoided.
_____test positive (3-5 days).
Biochemical test with diphenolic substrate (Confirmatory:(2)), the phenol oxidase (or laccase) of C. neoformans & C. gattii produces melanin in the cell walls and colonies develop a brown pigment.
cycloheximide
Urease
Staib’s Birdseed agar or Caffeic Acid/niger/bird seed medium
Cryptococcosis
______: whitish mucoid colonies within 2-3 days;
brown on____agar
_____- blastoconidia only without true hyphae or pseudohyphae
_____ - C. gattii uses glycine & nitrogen, C. neoformans does not
SDA
Staib agar
Cornmeal agar
Canavanine glycine bromothymol agar
C neoformans
C gatii
cycloheximide
S
R
Cryptococcosis
Serology: Antigen detection
• CAPSULAR POLYSACCHARIDES
o Long, unbranched polymers of a-1,3-linked branchen or evose and glucuronic add monomeric
•__________
o Solubilized in spinal fluid, serum, urine
• Detected by enzyme immunoassay or agglutination of latex particles coated with antibody to the polysaccharide
• With proper controls, this test is diagnostic of cryptococcosis.
Glucoronoxylomannan (GXM)
Cryptococcosis
B. SEROLOGY
• 90% of patients with cryptococcal meningitis - POSITIVE to_______.
o With effective treatment, titer drops, except in AIDS patients (often maintain high antigen titers for long periods.
• Newest test for GXM is______, with monoclonal antibodies to GXM, prepared in an ElA format on a dipstick. CSF, serum or urine produces positive test color change within 20 minutes, used as a point-of-care screen for cryptococcosis in sub-Saharan Africa.
latex slide agglutination or enzyme immunoassay
lateral flow assay (LFA)
Cryptococcosis
B. SEROLOGY
•: C neoformans var. grubii (most common in human
infections)
•: C neoformans var. neoformans (less common, still significant)
•. C gattii (found primarily in tropical & subtropical countries)
•: C gattii (found primarily in tropical & subtropical countries)
Serotype A
Serotype D
Serotype B
Serotype C
Cryptococcosis
Epidemiology/Ecology
• ____enrich the growth of C. neifrmans a reservoir of infection
• AIDS, SOT recipients, hematologic malignancies, patients maintained on corticosteroids are highly susceptible
• Sub-Saharan Africa is the epicenter of____
• Majority of global cases caused by C. neoformans (serotype A); C. gatti in the Pacific Northwest of the US
Bird droppings (particularly pigeon droppings)
HIV/AIDS
ASPERGILLOSIS
> Occurring worldwide, it is a spectrum of diseases that may be caused by a number of Aspergillus species
• Agents:
•_______ (most common)
+ 4
Aspergillus fumigatus
• A flavus
• A niger
• A terreus
• A lentulus
ASPERGILLOSIS
______: produce abundant small conidia that are easily aerosolized
INHALATION of_____: hosts develop severe allergic reactions to the conidial antigens. In immunocompromised patients (esp. leukemia, stem celli transplant, corticosteroids), the conidia produce hyphae that invade the lungs and other tissues.
MOLDS
CONIDIA
Morphology & Identification
• Aspergillus species:
• Grow rapidly, producing aerial hyphae that bear characteristic conidial structures:
long conidiophores with terminal vesicles on which phialides produce basipetal chains of conidia
• Species identified according to morphologic differences: size, shape, texture, & color of the conidia.
ASPERGILLOSIS
- Pathogenesis
In the lungs, alveolar macrophages are able to engulf and destroy the conidia.
However, macrophages from corticosteroid-treated or immunocompromised patients have a diminished ability to
contain the inoculum.
In the lung, conidia swell and germinate to produce hyphae that have a tendency to invade preexisting cavities
(aspergilloma or fungus ball) or blood vessels.
ASPERGILLOSIS
ASPERGILLOSIS - Clinical Findings
A. Allergic Forms
• Allergic bronchopulmonary aspergillosis - Atopic individuals develop IgE antibodies to surface antigens of Aspergillus conidia
• immediate asthmatic reaction; type | & IIII
hypersensitivity, eosinophilia, recurrent infiltrates
• Extrinsic allergic alveolitis - normal hosts, massive doses of conidia
ASPERGILLOSIS - Clinical Findings
- patients with cavitary disease (TB, sarcoidosis, emphysema) at risk; conidia in existing cavity produce abundant hyphae.
• localized, noninvasive infections/colonization of species may involve the nasal sinuses, the ear canal, or the nails
• Fungus ball
Aspergilloma & Extrapulmonary
Colonization
ASPERGILLOSIS - Clinical Findings
- an acute pneumonic process with or without dissemination - GIT, kidney, liver, brain, bones, etc.
(lymphocytic/myelogenous leukemia, lymphoma, stem cell transplant recipients,
corticosteroids taker, AIDS with less than 50 CD4 cells/ul at risk)
• Hyphae invade lumens, walls of
blood vessels = thrombosis,
infarction, and necrosis
• Without rapid treatment, prognosis is grave.
Invasive Aspergillosis
ASPERGILLOSIS - Clinical Findings
______: Keratitis and endophthalmitis
Ear infection:______
Cutaneous aspergillosis
Nail bed infection:_____
Mycotoxicosis
Ocular aspergillosis
Otitis externa
Onychomycosis
Asprgillosis
Caused by the ingestion of toxins produced by molds found in food, especially grains and nuts.
: aflatoxins, ochratoxin A, patulin, fumonisins, zearalenone and nivalenol/deoxynivalenol.
Mycotoxicosis
Mycotoxins
ASPERGILLOSIS - Diagnostic Laboratory Tests
A. Specimens, Microscopic Examination and Culture
• Sputum, other resp. tract specimens, lung biopsy tissue (blood, rarely positive)
• KOH or calcofluor white, histologic sections
• Species identified by culture Czapek Dox agar) - morphology of conidial structures
• Aspergillus diagnostic
hyphae - hyaline, septate, uniform in width (about 4um), branch dichotomously
Uniform, branching septate hyphae (ca. 4 um in width)
Macroscopic appearance of colony
Colonies -smoky green, velvety to powdery, reverse is white
Colonies yellow green, velvety, reverse is white
Colonies black, cottony type, reverse is white
A. fumigatus
A. flavus
A. niger
Microscopic appearance of colony (LPCB mount)
Vesicle is conical-shaped
Phialides are arranged in single row
Conidia arise from upper third of vesicle
Conidia are hyaline
A. fumigatus
Microscopic appearance of colony (LPCB mount)
• Vesicle is globular-shaped
• Phialides in one or two rows
• Conidia arise from upper two-third to entire vesicle
• Conidia are hyaline
A. flavus
Microscopic appearance of colony (LPCB mount)
Vesicle is globular-shaped
Phialides in two rows
Conidia arise from entire vesicle
Conidia are black in color
A. niger
ASPERGILLOSIS - Diagnostic Laboratory Tests
Uniseriate, columnar conidial heads with the phialides limited to the upper 2/3 of the vesicle and curving to be roughly parallel to each other
Aspergillus fumigatus
ASPERGILLOSIS - Diagnostic Laboratory Tests
One of the most potent mycotoxins is aflatoxin, which is elaborated by it and related molds and is a frequent contaminant of peanuts, corn, grains, and other foods.
A flavus
ASPERGILLOSIS - Diagnostic Laboratory Tests
Aspergillus terreus
ASPERGILLOSIS - Diagnostic Laboratory Tests
A niger
Aspergillosis
Serology
• Immunodiffusion test for precipitins to______ = positive
in over 80% of patients (aspergilloma or allergic forms)
• Serologic test for circulating cell wall______ = diagnostic for invasive
aspergillosis
A. fumigatus
galactomannan
Aspergillosis
Amphotericin-B resistant strains -(3) = posaconazole may be effective
A terreus, A flavus, A lentulus
Aspergillosis
Epidemiology
• Avoid exposure.
• Use filtered air-conditioning systems
• Monitor airborne
contaminants in patient’s room
• Reduce visiting
• Isolate patient
