Micro: Oppurtunistic Fungi And Yeast

Front 1

What is the ecology and epidemiology of C. neoformans?

Back 1

found in soil and associated with pigeon droppings; gains entry into the body via inhalation

there are two forms: cryptococcoma and diffuse penuomonitis; CNS involvement cause Meningitis

risk of developing meningitis is greatly increased in immunodeficient host esp those with Hodgekins, other reticuloedothelial defects, chronic lymphoblastic leukemia, sarcoid, lung carcinoma, SLE and AIDS

Front 2

What special property C. neofrmans allows it to survive and multiply in such an environment?

Back 2

its a HEAVILY ENCAPSULATED yeast

ALSO it is able to utilize creatinine as its sole source of nitrogen

reproduces by budding

Front 3

How is C. neoformans acquired?

Back 3

inhalation of organism

found in 1 micrometer of soil, allows for easy uptake by alveolar macrophages

Front 4

What is an important cell component of the yeast C. neoformans?

Back 4

polysacchride capsule
- fibrils of capsule surround the organism
- fibrils repell India ink --> negative stain

muccicarmie stains the polysacchride capsule

Front 5

Whay has there been a tremendous increase in the cases of meningitis due to C. neoformans?

How do you treat these cases?

Back 5

it is the most common clinical presentation esp in patients with AIDS

organism is never completely cleared from the body

lack of effective CMI prevents elimination of orgs from body

treat with amphotericin B + flucystosine

Front 6

What is the most sensitive and specific test for diagnosing disease due to C. neoformans?

What other method is used to examine CSF in the clinical lab?

Back 6

Cryptococcal Latex Agglutination Test
- serological test for polysacchride capsule Ag

India ink stain

Front 7

Diseases cause by C. albicans are quite varied. How is the organism acquired?

Back 7

acquired endogenously
- exists as normal flora of respiratory, GI, and female genital tracts
- found in all women during pregnacy
- by age 1 every one has positive skin test

Front 8

What are some of the factors that predispose individuals to infections with Candidiasis?

Back 8

1) local factors
- disruption of skin; having your hands in water all day; poor fitting dentures

2) intrinsic factors
- age, young childrean more susceptible; pregnancy; diabetes, malignacies, leukemias and lymphomas

3) Extrinsic Factors
- antibiotics; corticosteroids; surgery; trasnplantation (immunosuppressive therapy); oral contraceptive use

Front 9

Are blood cultures for C. albicans useful as definitive proof of life threatening infections?

If the clinical laboratory tells you that you have grown 10^6 colonies of C. albicans in a urine culture from a patient, is that significant?

Back 9

Isolation from blood is diagnostic of disseminated infection only

No. Most patients on broad spectrum antibiotics have candidiasis overgrowth

Front 10

In clinical laboratories how is C. albicans identified?

Back 10

Positive Germ tube test (serum at 37@)

If Germ tube test is negative, further identification using assimilation tests

Cornmeal Agar - all species produce hyphae, C. albicans also produces chlamydospores

Front 11

What do you see in a direct mount or histopathology of tissue infected with Candida?

Back 11

pseudohyphae and budding yeast

germ tubes at 37 degrees

Front 12

What is Chronic mucocutaneous candidiasis (CMC)?

Back 12

separate entity which generally begins early in life and is associated with polyendocrine disorders or defects of the immune system

all patients have defects in T-Cell Immunity

never develop life threatening Candida infections

Front 13

What is Systemic (Disseminated) Candidiasis?

Back 13

the organism invades the organ system of a debilitated or immunocompromised host; manifest by several life threatening conditions

Candida esophagitis
Candida endocarditis
Opthalmitis
systemic candidiasis of liver, kidney and bone marrow

Front 14

How do Aspergillus species act on the lung?

Back 14

1. may act as allergens causing asthma and bronchitis in sensitized patients - allergic aspergillosis

2. occur as saprophytes in lung cavities or dead areas of lung tissue - aspergilloma

3. may actively invade the living lung parenchyma in pts with reticuloendothelial disease - pulmonary aspergillosis

Front 15

What is seen in histopathology of apsergillosis?

Back 15

dichotomous branching 45 angle (septate hyphae)

Allergic Aspregillosis - infiltration of polymorphs and lymphocytes

Front 16

What factors predispose to the development of an Aspergillus fungus ball?

Back 16

long term immunosuppresion

old tuberculous or bronchiecstatic cavity, or infarct

Front 17

What are the factors that predispose to Zygomycosis?

Back 17

altered metabolism and decrease immunological response

diabetes --> mucormycosis

Front 18

What is seen int he histopathology of zygomycosis?

Back 18

hyphae are broad and aseptate

seen as short branche filaments that are often very distorted or collapsed

hypahe contain protoplasm, which stains haematoxylin, or appear empty

walls are very thin

Front 19

What are the characteristics of the organisms?

Are they septate or non septate?

Back 19

commonly isolated from soil and water

aseptate and form asexual spores in a sporangium

Front 20

Of which organ do the zygomycetes have a marked tendency for invasion?

Back 20

marked tendency to invade blood vessels --> thrombosis, occlusion and infarction by necrosis

Front 21

What is associated with the pathogenecity of C. albicans?

Back 21

transformation from a yeast to a hyphal form