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43 Cards in this Set
- Front
- Back
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What are the organisms causing opportunistic mycoses?
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Candida spp.(most common)
Cryptococcus spp. Aspergillus spp. Pneumocystis jiroveci |
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What are the causative agents of mycoses? where are they found?
What are the risk factors and who is at risk? |
Saprophytes ***Any fungus found in nature has potential to give rise to an opportunistic mycosis***
Found in soil/air/water At risk: Immunosuppressed RF's: Smoking, Pregnancy, Age |
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What are the charcteristics of Candida (Candidiasis)?
What species are capable of infection? |
-Most common
-Normal flora (skin, mucosa, GI) -Colonize mucosa after birth -Always present potential for infection -Cellular immunity protects against mucocutaneous candidiasis -Neutrophils protect against invasive candidiasis C. albicans (50%)/C.dubliniensis C.parapsilosis (10-25%) C.tropicalis (20-30%) C.glabrata (10-25%) |
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What are the most common infectious forms of Candidiasis?
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C. albicans
C. dubliniensis C. tropicalis |
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Pt presents with a candidiasis strain that is not responding to azole chemotherapy treatment. What organism do you suspect?
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C. glabrata
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What are some morphological features of candidiasis?
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Cream-yellowish colored colonies
Rapid growth at 37oC Oval/budding yeast cells at 37oC Produce pseudohyphae (budding cells fail to separate) More pseudohyphae = more invasive. Increased size = evasion (phagocytosis) Increased surface area = target cells adhesion. |
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What is the only species that produces only yeast cells (no pseudohyphae, no germ tubes)?
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C. glabrata
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What Candidiasis species are capable of forming true hyphae (Germ tube) when both rabbit serum and 37C are present?
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C. albicans
C. dubliniensis |
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Germ tube producing cells yields a large increase in what?
If your medium is nutritionally deficient medium, Candidiasis will form what? |
Virulence Factors
Large spherical chlamydospores (protect cells from harsh environmental conditions) |
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What method is used to differentiate C. albicans from C. dubliniensis?
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Carbon assimilation test:
C.albicans grows on trehelose/xylose containing media as a sole carbon source C. dubliniensis CANNOT grow using trehelose/xylose containing media |
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Describe the characteristics of Candida Pathogenicity.
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Attachment-possible by all forms and all species
Adherence to plastic surfaces (catheters) Proteases destroy host defense proteins (including IgA) Phospholipase aids host cell destruction. Enolase allows growth in harsh conditions. Heat shock proteins protect from increased body temperature. |
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What are risk factors for a Candidiasis infection?
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Any Immunosuppression:
Physiological: Age, Pregnancy Traumatic: Burn, Infection Hematological: AIDS, lymphoma, aplastic anemia, cellular immune deficiency Endocrinological: Hyperthyroidism Iatrogenic- oral contraceptives, steroid use, chemotherapy |
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What are 3 types of Candidiasis clinical manifestations?
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Cutaneous and Mucosal Infections
Systemic Candidiasis (Candidemia) Chronic Mucocutaneous Candidiasis |
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An AIDS Pt comes in with whitish lesions on his gums, lips, mouth, and palate. You diagnose him with....
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Oral (thrush) (AIDS pt's)
(epithelial cells, yeast, pseudohyphae) (Except for C. glabrata) Other cutaneous manifestations: Vulvovaginitis (diabetics) Dermatitis Onychomycosis Diaper Rash (not the only cause) |
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Your patient has a systemic candidiasis (candidemia) infection from a skin abrasion, how do you know they are immunocompentent vs. immunocompromised?
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Immunocompetent = Transient infection
Immunocompromised = Infections anywhere (kidneys, eye, heart and meninges) Other routes of infection: catheters, surgery, IV drug use, damage to skin or GI tract |
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Your patient has had a long standing Candidiasis infection of the skin and mucous membrane since early childhood. What is the underlying cause?
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Genetic defect in cellular immunity or endocrinopathy
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Your patient has a candidiasis infection. Your colleague takes a sputum sample for identification of the organism. Do you agree? What are some other samples that can be obtained?
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***Sputum samples CANNOT be used for identification-since Candida is part of the normal flora***
Others sampls: Blood - reveal systemic vs transient Swabs and scrapings CSF Tissue - skin lesions = confirmatory Catheter samples |
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Your doing a direct examination of a a candida under the microscope, what do you see?
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Gram-stained samples:
G+ round cells (bigger than bacteria) Hyphae and pseudohyphae Skin and nail samples: stained with 10% KOH and calcofluor white |
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What are some cultures used for Candidiasis Dx Laboratory Tests? Which species can you ID from direct examination?
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Media:
Potato Dextrose (PDA) Saboraud’s Dextrose (SD) Chromagar Observe hyphae for pseudohyphae Germ tubes or chlamydospores = C. albicans C. dubliniensis Other species = ID via biochemical tests |
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Why is a Candida culture not the best route for organism identification? What are some other test you could do and why?
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Limited b.c organism is part of the normal flora
Not sensitive -Exposure to previous Candida infection -Titers not developed until late infection Latex Agglutination Test -Reactive to mannan antigen -Limited sensitivity ELISA -Reactive to mannan antigen -Limited in sensitivity and specificity Test for circulating β-glucan -Under trials -Not currently available clinically |
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Your patient is immunocompetent but has an identified Candida infection. What organism is responsible? How did they get it?
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Cryptococcus gattii - does NOT require immunocompromised status
Cryptococcus neoformans - requires immunocompromised status Soil and bird droppings Inhalation of dried/dessicated yeast |
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Your patient is diagnosed with meningoencephalitis. Your culture of the specimen shows spherical budding cells with thick nonstaining capsules. What enzyme does your organism produce that created a black/brown color on the agar?
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Only C. neoformans and C. gatti grow at 37oC and produce laccase* an enzyme that catalyzes formation of melanin from phenolic substrates.
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*India Ink + thick capsule + fungal infection is ALWAYS.......
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Cryptococcus
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You perform a serotype of your specimin (cryptococcus): and it is identified as AD, what organism is it? You follow up with a CGB culture and it doesnt grow.....
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Serotypes (A-D)
C. neoformans (A,D,AD) C. gatti (B,C) Based on capsule and biochemical tests Canavanine glycine bromothymol blue (CGB) medium C. gatti CAN grow blue on CGB C. neoformans CANNOT grow on CGB |
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What are the virulence factors for cryptococcus (cryptococcosis) and what do they do?
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Capsule Polysaccharide (CPS)-
Influences infection Depresses inflammation Inhibits phagocytosis Suppresses cellular/humoral immunity Laccase (Diphenol oxidase) - catecholamines --> melanin Bird seed agar/caffeic acid medium |
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A patient is suing the hospital because his brother died of Cryptococcal meningoencephalitis and he believes one of the staff members gave it to him. Is he right? Where could his brother contract the disease?
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***Disease is NOT communicable***
1. Inhalation of yeast cells 2. Primary pulmonary infection may be asymptomatic or mimic influenza 3. Can resolve 4. IC pt's - systemic infections: Yeast prefer CSF -Cryptococcal meningoencephalitis -S/s: fever, headache, stiff neck or change in mental status -CSF = Increased pressure, Increased cell count, Low glucose -May present with lesions on organs (including skin) -May disseminate to skin, adrenals, eye, bone, and prostate ALL cases of cryptococcal meningoencephalitis are fatal (occurs in 5-10% of AIDS patients) |
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You sample a patient's urine for a cryptococcal species...what do you stain the wet mount with?
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Other samples: urine, blood, sputum, CSF
2. Wet mount stained with *India ink 3. ID via culture growth at 37oC and growth on CGB or diphenolic substrate (Birdseed agar) Observe brown or black color (specific to Cryptococcal species) Serology - Serum and CSF can be used to test for capsular antigens. a. Latex Slide Agglutination Test |
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What medium do you use to differentiate Cryptococcus from Candida?
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Bird Seed Agar (diphenolic substrate)
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What medium do you use to differentiate C. neoformans vs. C. gattii?
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Canavanine glycine bromothymol blue (CGB) medium
C. gattii CAN grow blue on CGB C. neoformans CANNOT grow on CGB |
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Aspergillus (Aspergillosis)
Who's in the Family? Where are they found? What is the overall pathogenesis of the organism? |
A. fumigatus (most common)
A. niger A. flavus A. terreus Occurs worldwide: Ubiquitous in nature Reservoir: air and soil *pt's that kick up dirt, construction* *Must be Immunosuppressed* -Powdery mold produces many small conidia that aerosolize -Inhalation-->severe allergic responses to conidia -IC pt's:conidia germinate-->hyphae (infect lungs) |
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What are the risk factors for contracting Aspergillus (Aspergillosis)?
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1. Immunosupression, DM (inhalation of spores)
2. Hypersensitivity reaction (inhalation spores) 3. Ingestion of products contaminated with Aspergillus toxins -Mycotoxicosis/hepatocellular and colon carcinoma |
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What is the morphology of Aspergillus (Aspergillosis)?
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Rapid Growth
Produces aerial hyphae with long conidiophores Species differentiated based on morphology of conidia -Mold spores differ in color Microscopically -Septate hyphae (dichotomous branching) is observed -Microconidia present |
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What is the pathogenesis of Aspergillus (Aspergillosis)?
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In IC pt's, conidia swell in the lung and germinate-->invade other tissue, cavities or blood vessels
-Aspergilloma (fungus ball) may develop |
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What are the clinical manifestations of an Allergic Aspergillosis, and what type of hypersensitivity are they?
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Asthma (Type I)
Allergic bronchopulmonary aspergillosis (Types I and III) |
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What is an Aspergilloma and what are some extrapulmonary colonizations associated with Aspergillus?
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Aspergilloma (Fungus Ball)
-Conidia enter preexisting cavity, germinate and produce hyphae in pulmonary space -Rarely invasive Otomycosis (external otitis) Onychomycosis Eye infections -(conjunctival, corneal, intraocular) |
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What are the clinical manifestations of an Invasive Aspergillosis?
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Fatal if untreated
Pulmonary Disseminated -GI, Brain, Liver, Kidney, Heart, Skin, Eye |
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What caused your patient's mycotoxicosis due to Aspergillus?
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Aflatoxin, it increases the severity of infection
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You suspect Aspergillus, what are some diagnostic tests you could perform? What sample can you not take?
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1. Specimens (sputum, lung tissue biopsies)
* DONT take blood samples* 2. Microscopy -Direct examination following KOH -Observe for hyphae 1. Hyaline 2. Septate 3. Uniform in width Culture: SDA (*grow 2!!) Serology -Allergy (serum IgE detection) -Invasive infections (ELISA: serum galaktomannan antigen (cell wall) detection) |
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Describe Pneumocystis jiroveci (Pneumocystis pneumoniae).
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Yeast like fungus
(yeast-related to ascomycetes) Distributed worldwide: No known natural reservoir Present in the lungs of animals Causes disease in IC persons Now considered normal flora Does NOT cause disease in healthy individuals |
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Describe the 2 forms of Pneumocystis jiroveci and its relation to AIDS patients.
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2 forms:
1. Trophozites (thin walled) -*Dividing/Replication 2. Cysts (thick walled) -*Protection/Infection form -Spherical -Multinucleate -Stained with toluene blue, calcofluor white, or silver stain -Usually found present in a tight mass in clinical settings Complete life cycle is NOT known Extracellular pathogen: Needs severe defects in B/T cell functions (AIDS) |
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What are the symptoms of Pneumocystis Pneumonia?
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(Atypical Pneumonia + High Fever)
Fever Non-productive cough Shortness of breath Weight loss Night sweats |
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What is the pathophysiology of Pneumocystis jiroveci?
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1. The disease attacks the interstitial fibrous tissue of the lungs
2. Results in thickening of the alveolar septa and alveoli 3. Leads to hypoxia which can be fatal if not treated |
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How do you diagnose Pneumocystis jiroveci?
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1. Chest x-ray:
Widespread pulmonary infiltrates 2. Identification: -Pneumocystis CANNOT be cultured -Observe lung biopsy tissue, sputum or specimens from a brochioalveolar lavage for cysts or trophozites -Cysts can be stained with toluene blue, calcofluor white or silver stain -PCR-based testing +'s do NOT diagnose Pneumocystis -Healthy individuals can carry the fungus |
