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Year 2 > Fungal Infections > Flashcards

Fungal Infections Flashcards

1
Q

What type of cells are fungi

A

Eukaryotic

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2
Q

What is their cell wall made of

A

Chitin

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3
Q

Fungi are heterotrophic, what does this mean?

A

An organism that can’t manufacture its own food and instead obtains its food and energy by taking in plant and animal matter

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4
Q

How does fungi ‘grow’

A

Produce spores which move through water and air

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5
Q

Why is fungus so infectious

A

High reproductive rate

Slow death so can spread before numbers thin

Broad host range

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6
Q

Yeast vs Mould

A
  1. Yeast - single celled
    Mould - multicellular
  2. Yeast divide by budding whilst moulds develop from hyphae
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7
Q

What are dimorphic fungi

A

They can switch from being yeast to mould depending on the environment

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8
Q

What is hyphae

A

Branching from the cell wall

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9
Q

Example of a dimorphic fungus

A

Coccidiodes immitis

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10
Q

Ideal conditions for C immitis

A

Warm, arid conditions

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11
Q

When does C immitis grow as mould

A

ambient temperature

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12
Q

How is C immitis spread

A

Light so by wind

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13
Q

When do C immitis convert from mould to yeast

A

At body temperature after inhalation

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14
Q

What disease does C immitis cause

A

Pneumonia

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15
Q

Why do not many fungi cause human infection

A
  1. Denature at 37 degrees

2. Our strong immune responses

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16
Q

How common are life-threatening fungal infections

A

Very uncommon

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17
Q

What is Otitis Externa

A

Inflammation of external ear canal

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18
Q

What is Onychomycosis

A

Final nail infection

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19
Q

What is Tinea Pedis

A

Athlete’s foot

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20
Q

Name five fungi which can cause life-threatening disease in immunocompromised hosts

A
  1. Candida
  2. Invasive aspergillosis
  3. Pneumocystis
  4. Cryptococcosis
  5. Mucormycosis
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21
Q

What does candida commonly cause in the mouth

A

Thrush

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22
Q

Why does Invasive aspergillosis take place

A

Cause the immune system can’t stope spores from reaching the bloodstream via the lungs

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23
Q

What does invasive aspergillosis often cause

A

TB

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24
Q

Two life-threatening fungal diseases in healthy hosts

A
  1. Fungal asthma

2. Travel associated fungal infections

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25
Q

Four characteristics of selective toxicity drugs for fungal infections

A
  1. Target receptors not in humans
  2. Target receptors is different to any human analogues
  3. Drug is concentrated in organism cell
  4. Increased permeability to compound
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26
Q

How do human cells survive selective toxicity drugs

A
  1. They use alternative metabolic pathways
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27
Q

Why is selective toxicity more difficult for fungi than bacteria

A

Eukaryotic

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28
Q

Four components of the final cell wall

A
  1. Mannoproteins
  2. B1,3, gluons
  3. B1,6 gluons
  4. Chitin
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29
Q

What is the plasma membrane of fungus made of

A

Ergosterol

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30
Q

Difference in composition of plasma membrane in humans and fungus

A

1, Humans have cholesterol in wall whilst fungi have ergosterol

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31
Q

What is an amphoteric molecule

A

A molecule with both acid and alkaline properties

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32
Q

What do amphoteric drugs act on in fungal cells

A

Drugs bind to ergosterol in membrane forming pores in membrane, k+ leakage and death

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33
Q

Why are polyenes like amphoteric drugs selective

A
  1. 10 times lower affinity for cholesterol in mammalian membrane s
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34
Q

Does this mean polyenes can’t cause damage in host cells

A

No, they can (dose dependant)

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35
Q

What are side-effects of polyenes

A
  1. Anaphylactic reactions, hypotension
  2. Hyperkalemia
  3. Hypokalaemia if distal renal uses are effected
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36
Q

Describe the ergosterol synthetic pathway

A

Acetyl CoA -> Farnesyl Pyrophosphate -> Squalene -> Squalene Eposide
-> Lanosterol -> 4,4-dimethylcholesta-8,14,24-trienol -> 4,4-dimethyltrymosterol -> Fecosterol -> Episterol -> Ergosta-5,7,24(28)-trienol -> Ergosterol

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37
Q

What type of drug is Terbinafine

A

Allylamines

38
Q

How does Terbinafine work

A

Reversible inhibition of squalene epoxidase

39
Q

What is the bioavailability of Terbinafine

40
Q

Where is Terbinafine usually metabolised

A

First pass metabolism in the liver

41
Q

Where is Terbinafine distributed to

A

Poorly perfused sites (skin and nails)

42
Q

What is Terbinafine usually used to treat

A

Dermatophytes (Candida, aspergillus)

43
Q

Two side-effects of Allyamines

A

Taste disturbance, deranged LFT, increased CYP450 metabolism

44
Q

What do azoles inhibit

A

Lanosterol

45
Q

Role of triazoles

A

Inhibit secondary targets in synthetic pathways

46
Q

Name an azalole used to inhibit lanosterol

A

Fluconazole

47
Q

What are clotrimazole and Ketoconazole active against

48
Q

Adverse effects of azoles

A
  1. Transaminitis

2. GI SEs

49
Q

Adverse effects unique to itraconazole

A

Nausea, diarrhoea

Liver failure

50
Q

Adverse effects unique to Voriconazole

A

30% suffer from reversible visual disturbances

51
Q

Why do azole drug-drug interactions occur

A
  1. Result of CYPP450
52
Q

Why are azole drug-drug interactions so rare for Fluconazole

A
  1. Hydrophilic and easily excreted
53
Q

What does Fluconazole inhibit

A

Warfarin, phenytoin, anxiolytics

54
Q

Which is a stronger inhibitor, intra or post

55
Q

What does Itraconazole and Posaconazole inhibit

56
Q

What does Voriconazole inhibit

A

CYP enzymes (some of the smaller ones)

57
Q

Why are Candida displaying azole resistance

A
  1. Mutations in ERG11 gene
  2. Increased expression for ERG11
  3. Causes efflux
58
Q

What drugs are most effected by azole resistance in Candida

A

Fluconazole and Voricaonzole

59
Q

What do Echinocandins inhibit

A

1,3 beta-glucan synthase

60
Q

Define fungistatic

A

Inhibit growth of fungus

61
Q

What type of cells are Echinocandins fungistatic towards

A

moulds at hyphen tip

62
Q

What the of cells are Echinocandins fungicidal towards

63
Q

What cell are resistant to Echinocandins

A
  1. Species with large amounts of 1,3 gluten in cell wall
64
Q

What species are resistant to Echinocandins

A
  1. Zygomycetes
  2. Cryptococcus
  3. Trichosporon
  4. Fusarium
65
Q

What is inconvenient about Echinocandins

A
  1. Poor oral bioavailability (IV only)

2. Poor penetration in some parts of the body (CSF, eye)

66
Q

What is a convenience of Echinocandins

A

Limited, and rare drug toxicity

  1. Concentration dependant killing
  2. Prolongues antibiotic effect
67
Q

What fungal infection does this patient have

  1. 60 yr old man has acute gallstone pancreatitis with pseudocysts
  2. Stable on transfer
    1 week later:
  3. Febrile >38 despite antibiotics
  4. Haemodynamics relatively stable
  5. Fungal infection found in line tip and blood
A

Invasive Candida infection

68
Q

How can we maximise sensitivity for fungi during diagnosis

A
  1. Pick up from tissue and fluids if can be obtained (best place to pick up)
69
Q

Blood culture efficiency for fungi vs bacteria

A

Blood culture only half as sensitive n fungi

70
Q

Why can we detect if there is a fungal infection within the body by using blood

A
  1. 1,3 gluten released by cell membrane into plasma
71
Q

Inconveniences of blood samples for fungi

A
  1. Prone to contamination

2. Non-specific for individual fungi

72
Q

Most common Candida in hospital patients

A
  1. Candida albicans
73
Q

What two drugs are candida most susceptible to

A
  1. Echinocandins

2. Polyenes (ampotericin B)

74
Q

What fungal infection is this man suffering from:

  1. 43 year old
  2. Found unconscious
  3. Lesion on CT in brain
  4. Serum galactomanna found
A

Aspegillus

75
Q

How do we know the 43 year old man is suffering from Aspergillus infection

A

Because Galactomannan is found in Aspergillus cell walls as an antigen

76
Q

Two drugs that inhibit ergosterol synthesis

A

Azole

Allyamines

77
Q

Drug that inhibits formation of cell wall gluten

A

Echinocandin

78
Q

Drug that inhibits DNA and RNA synthesis

A

Pyrimidine (5-fluuorocytosine)

79
Q

Drug that inhibits microtubule assembly

80
Q

How common is Onychomycosis

81
Q

What is Onchomycosis caused by

A

Dermatophyte moulds

82
Q

When do dermatophyte moulds grow best

A

30 degrees

83
Q

What species causes Onchymycosis

A

Trichopyton Rubrum

84
Q

What is the most specific test for Onchymycosis

A

Microscopy (30% culture negative)

85
Q

Two treatment options for Onchymycosis

A
  1. Topical Amorolfine

2. Itraconazole and Terbinafine

86
Q

What is Amorolfine

A

Morpholine

87
Q

How does Amorolfine work

A

Stops production of ergosterol

88
Q

What fungus has caused the following:

  1. 75 yrs old
  2. Admitted with onset respiratory failure
  3. Pulmonary oedema was primary diagnosis
  4. Beta gluten positive
A

Could be any cause every fungus has 1,3 gluten.

HOWEVER, since it effects the lungs it is pneumocystis

89
Q

When is pneumocystis most common

A

Early in life

90
Q

What patients usually get pneumocystis later in life

A

Immunocompromised

91
Q

What clinical indication for pneumocystis is there

A
  1. Hypoxia is more severe than tests are suggesting

Year 2 (155 decks)

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