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Fungal infections Flashcards

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1
Q
  1. List three examples of:
    a. Yeast

b. Moulds

A 
a.	Yeast
Candida
Cryptococcus
Histoplasma (dimorphic)
b.	Moulds
Aspergillus
Dermatophytes
Agents of mucormycosis
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2
Q
  1. Describe the appearance of Candida under the microscope.
A

Single-celled organisms that replicated by budding

They are much bigger than bacteria

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3
Q
  1. Which systemic infections can be caused by Candida?
A

Septicaemia, endocarditis, meningitis

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4
Q
  1. List some patient groups that are at risk of invasive Candida infection.
A

VLBW infants
Immunocompromised
Patients on ITU (especially if they have lines in)
Patients receiving TPN (Toal parental nutrition)
Immunocompetent patients who have had antibiotic treatment

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5
Q
  1. List some agents that can cause candidiasis.
A

Candida albicans (MOST COMMON)
Candida glabrata
Candida krusei
Candida tropicalis

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6
Q
  1. Describe a screening test for candidiasis.
A

Candida albicans forms a germ tube

Can be identified by microscopy

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7
Q
  1. What is the acute treatment for candida?
A

Fluconazole – empirical for Candida albicans, topical nystatin (oral thrush) and clotrimazole (vulvovaginitis)

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8
Q
  1. Outline diagnostic tests used for candidemia.
A 
Swabs 
Blood cultures 
Beta-D glucan assay (serology)
Imaging 
Fundoscopy – for endopthalmitis
ECHO – endocarditis
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9
Q
  1. What type of agar is needed for culturing Candida?
A

Sabouraud agar – impregnated with antibiotics to prevent bacteria from outcompeting the fungi

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10
Q
  1. Outline the management of candidemia.
A

At least 2 weeks of antifungals after the last negative culture
Echinocandins – empirical for non-albicans infections
Take out any lines and repeat blood cultures every 48 hours

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11
Q
  1. What are the serotypes of cryptococcus and who do they affect?
A

Serotypes A and D – immunodeficient – C neoformans

Serotypes B and C – immunocompetent – C gattii

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12
Q
  1. What types of disease does Cryptococcus tend to cause?
A

Pulmonary, systemic and meningitic disease

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13
Q
  1. Which group of antifungals is Cryptococcus inherently resistant to?
A

Echinocandins

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14
Q
  1. What is the treatment of choice for Cryptococcus infection?
A

Ambisome (amphotericin B)

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15
Q
  1. Which patients are particularly at risk of cryptococcosis?
A

Impaired T cell immunity (AIDS)

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16
Q
  1. What does Cryptococcus gatii cause?
A

Causes meningitis in immunocompetent individuals in tropical countries
High incidence of space-occupying lesions in the lung and brain
Increasing resistance to amphotericin B

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17
Q
  1. Describe the appearance of Cryptococcus under the microscope.
A

Distinct capsule around the yeast
India ink can be used to stain
NOTE: the capsule is not always present

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18
Q
  1. Outline the treatment options for Cryptococcus infection.
A

3 weeks amphotericin B (ambisome) +/- flucytosine
Repeat LP for pressure measurement
Secondary suppression – fluconazole

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19
Q
  1. List the diseases that can be caused by Aspergillus.
A

Mycotoxicosis
Allergic bronchopulmonary aspergillosis
Aspergilloma
Invasive/disseminated disease

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20
Q
  1. List the aetiological agents that can cause Aspergillus infection.
A 
Aspergillus fumigatus 
Aspergillus flavus
Aspergillus niger
Aspergillus niduland
Aspergillus terreus
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21
Q
  1. List some investigations used in the diagnosis of Aspergillus infection.
Study These Flashcards
A 
Blood test 
Serology (check IgE for allergic response (e.g. ABPA))
•	Antigen detection (galactomannan) 
•	Also detected in BAL 
PCR 
Histology 
Culture
22
Q
  1. What is the mainstay of diagnosis of Aspergillus infection?
Study These Flashcards
A

Microscopy – looking at fungal spores

23
Q
  1. What is the mainstay of treatment for aspergillosis?
Study These Flashcards
A

Amphotericin for at least 6 weeks

Other options: voriconazole, caspofungin, itraconazole

24
Q
  1. What is used to treat pneumocystic pneumonia?
Study These Flashcards
A

High dose Co- trimoxazole (as it lacks ergosterol in its cell wall, therefore targeting the cell membrane will not work)

25
33. List some examples of dermatophyte infections.
Ringworm Tinea Nail infections
26
34. What is tinea pedis caused by?
Tricophyton rubrum Tricophyton interdigitale Epidermophyton floccosum
27
35. What is tinea cruris caused by?
Tricophyton rubrum | Epidermophyton floccosum
28
36. What is tinea corporis caused by?
Tricophyton rubrum | Tricophyton tonsurans
29
37. What is onychomycosis caused by?
Tricophyton spp. Epidermophyton spp. Microsporum spp.
30
38. How is onychomycosis treated?
Nail lacquers If unsuccessful, systemic treatment with terbinafine Itraconazole is also an option
31
40. What is pityriasis versicolor caused by?
Malassezia furfur
32
41. What is mucormycosis?
Group of moulds that cause very severe and invasive disease
33
43. What is the characteristic clinical manifestation of mucormycosis?
Cellulitis of the orbit and face which progresses with discharge and black pus from the palate and nose NOTE: black eschars may be seen as the fungus destroys tissues
34
44. What can retro-orbital extension of mucormycosis lead to?
Proptosis, ophthalmoplegia and blindness
35
46. List three aetiological agents that can cause mucormycosis.
Rhizopum spp. Rhizomucor spp. Mucor spp.
36
47. How is mucormycosis managed?
SURGICAL EMERGENCY Refer to ENT for debridement May need high-dose amphotericin
37
48. What are the three targets of antifungals?
Cell membrane DNA/RNA synthesis Cell wall
38
49. List antifungals that target: a. Cell membrane b. DNA/RNA synthesis c. Cell wall
``` a. Cell membrane Polyene – amphotericin B, nystatin Azole – ketoconazole, itraconazole, fluconazole, clotrimazole b. DNA/RNA synthesis Flucytosine (pyrimidine analogue) c. Cell wall Echinocandins – caspofungin acetate ```
39
50. What is the mechanism of action of azoles?
Inhibit ergosterol production by inhibiting CYP450 enzyme lanosterol 14 alpha-demethylase This inhibition leads to the accumulation of toxic steroids in the cell membrane which cause cell death
40
51. What are the consequences of cross-reaction of azoles with other CYP450 enzymes?
Drug interactions | Impairment of steroidogenesis
41
Which fungi are polyenes effective against?
all fungi except Aspergillus terreus and scedosporium
42
What is a side effect of polyenes
nephrotoxicity Renovascular – decrease in renal blood flow leads to reduced GFR (azotaemia) Tubular – distal tubular ischaemia, wasting of sodium, potassium and magnesium
43
54. What is the mechanism of action of echinocandins?
cyclic lipopeptide antibiotic that inhibits beta-(1,3) D-glucan synthase This enzyme is responsible for the production of beta D-glucan which is a component of the fungal cell wall This inhibition results in osmotic fragility of the cell
44
55. Which fungi are echinocandins active against e.g. Caspofungin?
``` Candida species Aspergillus species (NOT other moulds) ```
45
56. What is the main polyene antifungal?
Amphotericin B
46
57. How is amphotericin packaged in most formulations?
Put in liposomes to try and reduce toxicity and improve penetration e.g. ambisome - amphotericin within a phospholipid bilayer
47
60. Describe the mechanism of action of amphotericin B.
Binds to ergosterol in the fungal cell membrane and creates transmembrane channels leading to electrolyte leakage This leads to fungal cell death
48
What are the sifde effect of azoles?
impaired LFT
49
63. Describe the mechanism of action of flucytosine. Mechanisms of resistance?
Inhibits DNA synthesis (pyrimidine analogue) ``` Decreased uptake (permease activity) Altered 5-FC metabolism ```
50
65. Which fungi are flucytosine active against?
Candidiasis | Cryptococcosis

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