Fungi

Question 1

What species of candida accounts for 50% of all candida infections?

Answer 1

c. albicans

Question 2

How does oral candida infection occur?

Answer 2

usually the result of the outgrowth of an endogenous pop of candida organisms no longer held in check by innate body defenses

Question 3

What are the three main body defenses that usually help prevent candida from infecting the oral cavity?

Answer 3

saliva and normal bacterial flora and t cell mediated immunity

Question 4

For what kinds of patients is candida especially dangerous (ie. what cell deficiencies)?

Answer 4

t-lymphocyte defects or neutropenic pts with disseminated infection have very poor prognosis

Question 5

What is a fungal infection that is considered an AIDS-defining illness? What are associated problems?

Answer 5

candida esophagitis
dysphagia/difficulty swallowing. often consume soft carb-rich diets as a result- bad cycle, since such diets lower the environmental pH, which makes candida happy

Question 6

What are the morphologic forms of candida?

Answer 6

yeast, hypha, pseudohypha

Question 7

What is candida vulvovaginitis? what species cause this infection? How is it treated

Answer 7

“yeast infection”
candida albicans
candida glabrata (higher rates of treatment failure)
fluconazole

Question 8

What distinguishes C. albicans from other candida species?

Answer 8

ability to form germ tubes- nascent hypha from yeast forms

Question 9

What form(s) of candida is/are most adhesive?

Answer 9

germ tube and mature hyphae

Question 10

How does candida adhere to the oral cavity?

Answer 10

host transglutaminase interacts with candida integrin or proline-rich molecules to provide a stable, covalent attachment.

Question 11

How does C. albicans invade tissue?

Answer 11

growing hyphal tip actively penetrates tissue. facilitated by secretion of hydrolytic enzymes

Question 12

What are the three main layers of the candida cell wall?

Answer 12

mannoprotein layer
glucan layer
chitin layer

Question 13

What is the purpose of the mannan/mannoprotein layer in candida?

Answer 13

attachement and permeability barrier

Question 14

What is the role of the glucan layer in candida?

Answer 14

structural integrity of the cell

Question 15

What is the role of the chitin layer in candida?

Answer 15

structural role, esp. at the site of new cell formation

Question 16

What are polyene antibiotics? What are the two relevant drugs? How does it work?

Answer 16

example: amphotericin B and nystatin

this binds to ergosterol in the plasma membrane and increases its permeability.

Question 17

What are special considerations with the use of amphotericin B>

Answer 17

amphotericin B cannot be orally administered because its not water soluble.

Question 18

Are polyene antibiotics -cidal or -static drugs? Any special considerations/concerns?

Answer 18

cidal

yes! very low therapeutic window

Question 19

What are the azole derivatives (imidazoles and triazoles)? (examples) How do they work?

Answer 19

miconazole and fluconazole
perturb membrane stucture and function by inhibition of a cytochrome P450 analog which participates in the synthesis of membrane components

Question 20

What is miconazole? What class and how administered?

Answer 20

azole derivative (fungal P450 inhibitor and membrane synthesis disruptor)
topical application

Question 21

What is fluconazole? What class and how administered?

Answer 21

triazole derivative
P450 analog inhibitor- membrane synthesis disruptor
systemic admin

Question 22

Are azole derivatives -cidal or -static agents?

Answer 22

static

Question 23

Echinocandins. How do they work? Example?

Answer 23

caspofungin

target beta-glucans by inhibiting glucan synthesis

Question 24

Are echinocandins -cidal or -static agents?

Answer 24

cidal

Question 25

Flucytosine: how does it work? How administered? special considerations?

Answer 25

nucleic acid analog that inhibits DNA synthesis. good oral absorption relatively low toxicity but must be used in conjunction with other drugs because resistance develops easily

Question 26

What is cryptococcus neoformans? Who is susceptible? Morphology? reservoir?

Answer 26

most rapidly emerging fungal pathogen for AIDS pts yeast form only pigeon droppings and eucalyptus leaves

Question 27

What is the main virulence factor associated with cryptococcus neoformans? What is the main therapeutic challenge?

Answer 27

- polysacchride capsule | - reistant to echinocandins

Question 28

Aspergillus: who is susceptible? Where is it acquired? What happens during infection

Answer 28

- those with severe breakdown in cell-mediated defenses - acquired by inhalation of ubiquitous spores - grow as filamentous form at the site of infection to form a fungal ball or aspergilloma - secrete hydrolytic proteases

Question 29

How do you treat aspergillus infection?

Answer 29

amphotericin B

Question 30

What is dermatophytosis? What layer of the skin is infected? What are the two main genera?

Answer 30

fungal infection of keratinized tissue stratum corneum is infected trichophyton and microsporum

Question 31

What is an effective drug against the dermatophytes?

Answer 31

allylamines, like terbinafine/lamisil

Question 32

How do allylamines work?

Answer 32

inhibit squalene epoxidase, which is needed for ergosterol formation. leads to membrane disruption and cell death.

Question 33

What are two licensed allylamines?

Answer 33

lamisil/terbinafine and naftifine

Question 34

How is terbinafine administered? How is naftifine administered?

Answer 34

terbinafine is available both orally and topically | naftifine is only topical

Question 35

What are the 5 traits common to systemic mycoses caused by environmentally acquired fungi?

Answer 35

1. dimorphism- grow in yeast form at 37C (as mycelium at 25C) 2. route of infection- inhalation of spores 3. disseminated infection, esp. in immunocompromised 4. geographic predilection 5. immunologic response, usually granulomatous inflammation

Question 36

What are some symptoms of systemic mycoses?

Answer 36

often asymptomatic may present with severe pulmonary disease and weight loss you must differentiate btw systemic mycoses and TB

Question 37

Where is histoplasma capsulatum common? Where is it found in the environment?

Answer 37

ohio, mississippi and missouri river valleys found in bird and bat feces acute and chronic pulmonary infections

Question 38

Pathology of histoplasma capsulatum

Answer 38

reporduces inside macrophages usually asymptomatic some people get headaces, fevers, chills, cough, chest pain.

Question 39

Coccidioides immitis: where is it common geographically?

Answer 39

dsserts of northern mexico and SW US.

Question 40

Coccidioides immitis- typical presentations? severe presentations

Answer 40

often asymptomatic sometimes flu symptoms- fever, dry cough, eosinophili, etc. some get bone infection and meningitis (less than 1%)

Question 41

Blastomyces dermatitidis. where is it found geographically and environmentally?

Answer 41

soil of states east of the mississippi

Question 42

What are symptoms of bastomyces dermatitidis?

Answer 42

rarely asymptomatic usually pleuritic chest pain, fever, chills, productive cough severe cases involve weight loss, night sweats, skin ulcers, potential death. TREAT AGGRESSIVELY.

Question 43

Paracoccidioides brasiliensis: morphology. where is it from?

Answer 43

pilots wheel- multiple buds off a single parent cell | endemic to brazil and latin america

Question 44

What is the epi of paracoccidioides brasiliensis? What are the most common sites of infection?

Answer 44

- WAY more men than women (female hormones prevent infection?) - mouth and nose

Question 45

What are the four systemic mycoses?

Answer 45

coccidioides immitis, histoplasma capsulatum, blastomyces dermatitidis, and para coccidioides brasiliensis