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Microbiology > 5.46 Part B > Flashcards

5.46 Part B Flashcards

1
Q

Antifungal Drugs
• fewer effective agents because of similarity
of
• easier to treat — mycoses than — infections

A

fungal cells and human cells

superficial, systemic

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2
Q

ergosterol

A

Sterol found in fungal cell membranes;
human cells have cholesterol instead of
ergostero

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3
Q

Antifungal treatments

Polyene compounds -

A

bind ergosterol in fungal membranes

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4
Q

Polyene compounds

examples (2)

A

Amphotericin B systemic disease

Nystatin topical disease

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5
Q 
Polyene compounds - 
Drugs cause (3)
A

altered membrane
permeability,
leakage of cell constituents, and cell death

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6
Q

Polyenes also bind — in mammalian

cells, but less strongly than ergosterol

A

cholesterol

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7
Q

Polyenes also bind cholesterol in mammalian
cells, but less strongly than ergosterol
• this is basis for —
• — is toxic due to binding of cholesterol

A

drug toxicity

filipin

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8
Q

terbinafine (TFB) to

A

itraconazole (ITZ)

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9
Q

Allylamines-

A

block ergosterol synthesis by inhibiting

squalene epoxidase activity

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10
Q

Allylamines ex

A

terbinafine

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11
Q

Allylamines
mainly effective on the —
(2) formulations

A

dermatophytes

topical or tablet

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12
Q

Azoles

A

block ergosterol synthesis by inhibiting cytochrome

P450-dependent 14a-lanosterol demethylation

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13
Q

Azoles
First oral azole (significant number of
(2)).

A

side effect and drugs interactions

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14
Q

Supplants ketoconazole

A

Active against many fungi and has improved
safety profile. Active against Candida species,
Cryptococcus, Aspergillus, endemic (systemic)
fungi, and dermatophytes.

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15
Q

Echinocandins

A

inhibit synthesis of b-(1,3)-D-glucan, an
essential component of fungal cell walls.
More selective than agents that target cell
membrane components.

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16
Q

Echinocandins

Narrow spectrum:

A

active against Aspergillus and Candida species;

these fungi have larger amounts of b-(1,3)-D-glucan

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17
Q

Caspofungin (2)

A
  • Intravenous use

- minimal toxicity

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18
Q

Pyrimidine inhibition -

A

interferes with fungal protein and

DNA synthesis

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19
Q 
Pyrimidine inhibition
Active against (2)
A

Candida species and Cryptococcus neoformans

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20
Q

Pyrimidine inhibition

Always used in combination with another antifungal because

A

resistance

develops quickly if used alone

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21
Q

High risk categories (5)

A 
Immunocompromised individuals:
Burn victims
Long-term IV catheter users
Broad-spectrum antibiotic therapy
Diabetes mellitus
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22
Q

Immunocompromised individuals:

9

A 
blood and marrow transplant
solid organ transplant
major surgery
AIDS
neutropenia
neoplastic disease (cancer patients)
immunosuppressive therapy (e.g. corticosteroids)
advanced age
premature birth
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23
Q

Candida albicans

A

predominant species colonizing humans

responsible for most infections

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24
Q

Candida glabrata

A

resistant to some antifungals

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25
Candida parapsilosis
common cause of catheter-related infections
26
Candidiasis | local disease vs. systemic invasive disease
Adequate neutrophil function protects against invasive infection. Local factors and T-cell mediated defense system protects against mucosal candidiasis
27
Mucosal candidiasis on palate of a patient with AIDS Due to
decreased T-cell mediated immunity (however, no invasion of tissue here)
28
Other host factors associated with protection against Candida infections: (4)
salivary flow and constituents blood group & secretor status epithelial barrier presence of normal bacterial flora
29
candida infection: acute pseudomembranous acute erythematous clinical presentation:
multiple removable white plaques | generalized redness of tissue (ab sore mouth, painful)
30
candida infection: chronic plaquelike/nodular | clinical presentation:
fixed white plaques on commissures
31
candida infection: chronic erthematous | clinical presentation:
generalized redness of tissue on fitting surface of upper denture
32
candida infection: candidia associated angular chelities | clinical presentation:
bilateral cracks, angles of mouth
33
Thrush
Pseudomembranous candidiasis lesions on palate
34
Angular chelitis at commissures of the mouth, involving skin Frequently there is a --- component
bacterial
35
Plaquelike/nodular candidiasis | • Also called (2)
chronic hyperplastic | candidiasis or candidal leukoplakia
36
Plaquelike/nodular candidiasis • Up to --% of lesions develop into oral cancer
40
37
Candidiasis- diagnosis | Mucosal candidiasis
scrape and look under the microscope | culture
38
Candidiasis- diagnosis Invasive candidiasis (4)
blood culture not sensitive biopsy of involved tissue microscopy culture
39
Staining methods to visualize fungi in clinical samples: (5)
``` periodic acid-Schiff (PAS) potassium hydroxide (KOH) Grocott-Gomori methenamine silver Gridleys method Calcofluor white ```
40
periodic acid-Schiff (PAS)
-surface carbohydrate
41
potassium hydroxide (KOH)
-tissue dissolves, fungi do not (chitin)
42
Grocott-Gomori methenamine silver
-surface carbohydrate
43
Gridleys method
-modification of PAS
44
Calcofluor white
-fluorescent probe for chitin
45
why is candida auris a problem? (5)
``` it causes serious infections its often resistant to medicines its becoming more common its difficult to identity it can spread in hospital and nursing homes ```
46
C. neoformans is found worldwide in
soil contaminated with bird excreta
47
--% of patients with cryptococcosis appear to be immunocompetent.
20
48
Cryptococcus neoformans | Yeast cells are inhaled in alveoli and begin to produce a polysaccharide capsule. (3)
capsule inhibits phagocytosis and intracellular killing (if cells phagocytosed) T-cell immunity crucial to infection control melanin production in cell wall enhances virulence
49
Cryptococcus neoformans melanin production in cell wall enhances virulence resists
free radicals and enzyme degradation
50
Cryptococcus neoformans | Primary pulmonary infection is usually ---
asymptomatic
51
C. neoformans has a striking
neurotropism (basis is unknown) | minimal inflammatory response with CNS infection
52
Cryptococcus neoformans | Patients often present with ---, which worsens
meningitis
53
Cryptococcus neoformans | Diagnosis (2)
cryptococcal meningitis - examine CSF for encapsulated budding yeast latex agglutination test for capsular polysaccharide antigen (CSF fluid and serum)
54
Cryptococcus neoformans | tx
cryptococcal meningitis sometimes lifelong therapy required (patients with T cell defects)
55
Aspergillosis (2)
Aspergillus fumigatus and Aspergillus flavus
56
Aspergillosis | acquired from the environment by
inhalation of conidia
57
Aspergillosis | grow as --- in immunosuppressed individuals
hyphae | usually a pulmonary or sinus infection
58
angioinvasive - growth through cause (3)
blood vessel walls | tissue infarction, hemorrhage, necrosis
59
Aspergillosis | Diagnosis
culture on Sabourauds agar (grows in a few days) | caution: contamination from environment can easily occur
60
Aspergillosis | tx
high mortality expanded-spectrum azole voraconazole decreased exposure (filtered air)
61
Zygomycosis | (2) are main genera in this group
Rhizopus and Mucor
62
Zygomycosis (3)
aseptate, broad hyphae angioinvasive in addition to standard risk groups, patients with diabetes mellitus with ketoacidosis
63
in addition to standard risk groups, patients with diabetes mellitus with ketoacidosis
- acidosis reduces neutrophil chemotaxis and phagocytosis
64
Rhinocerebral zygomycosis-
spread from nares/sinuses to palate, orbit, face then to brain
65
Zygomycosis | tx
amphotericin B and | aggressive surgical debridement
66
Pneumocystis jiroveci -
organism has never been grown in vitro
67
Pneumocystosis | most people likely are infected early in life, but disease only occurs due to
immunosuppression (T cell deficiency most common risk factor)
68
Pneumocystic pneumonia
most common opportunistic infection in AIDS patients | before effective antiviral therapy
69
Pneumocystosis | Organism rarely found outside ---
lungs
70
Pneumocystosis | tx
- trimethoprim-sulfamethoxazole (also used prophylactically) target folic acid synthesis and utilization note: P. jiroveci lacks ergosterol

Microbiology (42 decks)

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