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Microbiology > Fungal Infections > Flashcards

Fungal Infections Flashcards

1
Q

What are fungi?

A

Eukaryotic organism that possesses chitinous cell walls, plasma membrane containing ergosterol, 80S ribosomes

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2
Q

What types of fungi exist?

A

2 types:

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3
Q

What is the commonest cause of fungal infections in human?

A

Candida spp.

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4
Q

What is candida? What is the clinical manifestations?

A

• A yeast and the commonest fungal infection
• > 150 Candida spp., but < 10 are human pathogens
• Clinical manifestations
– Acute, subacute, chronic, episodic
– Superficial or systemic/invasive

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5
Q

How can we differentiate types of candida on plates?

A

We use chromogenic agar plates - different appearances.

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6
Q

What’s wrong with Mr. X’s tongue?

A

Oral candidiasis.

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7
Q

What are the types of superficial candida infections?

A 
• Oral thrush
• Candida oesophagitis 
• Vulvovaginitis
• Cutaneous
– Localised or generalised
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8
Q

What tx is available for superficial candidiasis

A

Send for plates.

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9
Q

Which one is the yeast?

A

Left - larger, oval shaped.

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10
Q

What are the risks of candidaemia?

A

-

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11
Q

How do you manage candidaemia?

A

-

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12
Q

What are the invasive candida infections? How does tx differ?

A

-

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13
Q

What is cryptococcosis? How is it transmitted? How does it present?

A

-

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14
Q

Describe the lifecycle of cryptococcosis.

A

-

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15
Q

What are the RFs for cryptococcosis?

A

-

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16
Q

What type of ink is used for a cryptococcal stain?

A

India ink.

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17
Q

How is cryptococcosis treated?

A

-

18
Q

Where is Aspergillosis found? What diseases does it cause?

A

-

19
Q

What does this show?

A

An aspergilloma secondary to TB

20
Q

How can you diagnose aspergillosis?

A

-

21
Q

How is aspergillosis managed?

A

-

22
Q

Where is pneumocystis jiroveci found? How is it different? What is the route of transmission? What are the risk factors?

A

-

23
Q

How do you diagnose and manage pneumocystis pneumonia?

A

-

24
Q

What is Mucornycoses? What is it caused by? How is it transmitted? What are the RFs?

A
  • Clinical syndrome caused by a number of fungal species belonging to the order Mucorales eg Rhizopus, Rhizomucor, Mucor
  • Inoculation via inhalation of spores or primary cutaneous inoculation
  • Favours immunosuppressed/diabetic patients
25
Q

What are the clinical features of mucormycosis?

A

-

26
Q

What is the diagnosis and management of mucormycosis?

A

-

27
Q

What are dermatophytes? Where does it have effect?

A

-

28
Q

What are the investigations and management of dermatophytes?

A

• Dx
– Skin scrapings, nail specimens and plucked hairs
• MC&S
• Mx
– Topical eg clotrimazole, ketoconazole
– Oral eg griseofulvin, terbinafine, itraconazole

29
Q

What are azoles associated with?

A

Abnormal LFTs.

30
Q

What Polyenes associated with?

A

Nephrotoxicity

31
Q

What are echinocandins associated with?

A

Relatively innocuous

32
Q

What are pyrimidine analogues associated with?

A

Blood disorders

33
Q

What are the targets of antifungal therapy?

A

-

34
Q

What drugs target the cell membrane?

A

-

35
Q

How to azoles work?

A

• In fungi, the cytochrome P450-enzyme lanosterol 14-a demethylase is responsible for the conversion of lanosterol to ergosterol
• Azoles bind to lanosterol 14a-demethylase inhibiting the production of ergosterol
– Some cross-reactivity is seen with mammalian cytochrome p450 enzymes
• Drug Interactions
• Impairment of steroidneogenesis (ketoconazole, itraconazole)

36
Q

How do the polyenes work? What do we need to consider?

A

Amphotericin B

  • Polyene antibiotic
  • Fermentation product of Streptomyces nodusus
  • Binds sterols in fungal cell membrane
  • Creates transmembrane channel and electrolyte leakage
  • Active against most fungi except Aspergillus terreus, Scedosporium spp.

• Most significant delayed toxicity
• Renovascular and tubular mechanisms
– Vascular-decrease in renal blood flow leading to drop in GFR, azotemia
– Tubular-distal tubular ischemia, wasting of potassium, sodium, and magnesium
• Enhanced in patients who are volume depleted or who are on concomitant nephrotoxic agents

• Classic amphotericin B deoxycholate (FungizoneTM) formulation: serious toxic side effects
• Less toxic preparations:
1) Liposomal amphotericin B
2) Amphotericin B colloidal dispersion 3) Amphotericin B lipid complex

37
Q

What drugs target the cell wall?

A

-

38
Q

How do the echinocandins work?

A

-

39
Q

What drugs target DNA/RNA synthesis?

A
  • DNA/RNA synthesis • Pyrimidine analogues

- Flucytosine

40
Q

How does flucytosine work?

A 
-• Restricted spectrum of activity
• Acquired Resistance
– result of monotherapy – rapid onset
• Due to:
– Decreased uptake (permease activity)
– Altered 5-FC metabolism (cytosine deaminase or UMP pyrophosphorylase activity)

• Limited
– Candida and cryptococcosis
• In combination with Ambisome/fluconazole • Ses
– Infrequent – include D&V, alterations in liver function tests and blood disorders.
• Blood concentrations need monitoring when used in conjunction with Amphotericin B

Microbiology (19 decks)

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