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Pathology by week > Week 11 - Fungal infections > Flashcards

Week 11 - Fungal infections Flashcards

1
Q

Fungi are made of ____________ cells, their cell wall contains ___________, their plasma membranes contain ____________, and their ribosomes are _____

A

eukaryotic cells

cell wall contains chitinous

plasma membranes contain ergosterol

80S

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2
Q

Fungi are divided into two classes - name them, and state their difference

A

Yeasts - single-celled, reproduce by BUDDING

Moulds - multicellular hyphae, grow by BRANCHING and EXTENSION

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3
Q

Name 2 types of yeast and 3 types of moulds

A

Yeast:

  • candida
  • cryptococcus

Moulds:

  • dermatophytes
  • aspergillus
  • mucormycosis
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4
Q

What are dimorphic fungi? Name an example.

A

Dimorphic fungi exist as moulds at lower temperatures and as yeasts at higher temperatures

Example: histoplasma

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5
Q

What is the commonest cause of fungal infection in humans?

A

candida species

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6
Q

You are an FY1 on the MFE ward. The nurse is looking after F bay bleeps you saying Mr A is complaining of a painful mouth and his tongue looks strange.

What do you see?

A

Superficial candida infection = oral thrush

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7
Q

What do you see?

A

Superficial candida infection = cutaneous candidiasis

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9
Q

Which picture is the yeast?

A

left

same magnification

You see the yeasts are larger, they’re a bit more ovoid and much more prominent than G+ cocci bacteria

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11
Q

What is the treatment for:

  • Oral thrush?
  • Vulvovaginitis?
  • Localised cutaneous?
  • Oesophagitis?
A
  • Oral thrush => nystatin (topical)
  • Vulvovaginitis => cotrimazole (topical), or fluconazole (oral)
  • Localised cutaneous => cotrimazole (topical)
  • Oesophagitis => fluconazole (oral)
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13
Q

What colour do candida stain on Gram staining?

A

Candida will usually stain + on Gram stain due to thick polysaccharide around it

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14
Q

Name 4 risk factors for developing candidaemia

A
  1. Malignancies, esp haematological
  2. Burn patients
  3. Complicated post-op courses
  4. Long lines
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15
Q

Cryptococcus are most commonly associated with contact with ________

A

birds/pigeons

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16
Q

Name the steps (4) for management of candidaemia

A
  1. Look for source and signs of dissemination:
    - Imaging
    - Serology for beta- D-glucan
    - ECHO
    - Fundoscopy

* candida is sticky and could stick to heart valves and/or back of eyes (causing candida ophthalmitis)

  1. Antifungals for at least 2/52 (from date of 1st negative BC)
    - Echinocandin e.g. anidulafungin
  2. BC every 48 hours
  3. Remove any lines/prosthetic material
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17
Q

Name the 4 serotypes of cryptococci and the organism - which patients is each more common in?

A

Serotypes A & D = cryptoccous neoformans => IMMUNODEFICIENT

Serotypes B & C => cryptococcus gattii => IMMUNOCOMPETENT

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18
Q

You’re an FY1 on the medical take. A patient known to the HIV team who has refused ARVs has presented with fever, headache, and confusion. Your SpR has asked you to go and review the patient and clerk them in. There is an MRI already done. what do you see?

A

multiple cryptococcomas (CNS invasion of cryptococcus into parenchymal regions).

NOTE: cryptococcomas are a rare complication of infection by the Cryptococcus genus of invasive fungi, where a discrete, encapsulated lesion of immune infiltrates and pathogen forms.

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19
Q

How does cryptoccocus spread?

A

via inhalation of aerosolised organisms

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20
Q

India ink stain on CSF. What do you see?

A

massive capsule of organism in CSF = cryptococcus in CSF = CNS cryptococcal infection

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22
Q

What do you see in this culture?

A

Hyphae around pierphery that are branching off = aspergillus culture

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23
Q

You’re and FY1 on the resp ward. Consultant referred a patient from clinic who is experiencing haemoptysis and weight loss. PMHx includes treated pulmonary TB.

What is the diagnosis? Explain the haemoptysis

A

This is an aspergilloma – the aspergillus has found that scarred cavity from the previous infection to grow in.

If the aspergillus grows too large, it can invade into the pulmonary vasculature and cause haemoptysis

24
Q

What are the risk factors (2) for cryptococcus?

A
  1. Imapired T cell immunity
    - eg patients with HIV with reduced CD4 T cell counts of <200/ml

* extrapulmonary infection is an AIDS-defining illness

  1. Patients taking T cell immunosuppressants for solid organ transplantation (lifetime risk 6%)
25
Q

C gattii:

  • Does it affect immunocompetent or immunocompromised individuals?
  • Changes in brain and lung?
  • Geographic locations of infection?
A
  • Immunocompetent
  • causes meningitis; high incidence of SOL in brain/lungs
  • Tropical altitudes (SE Asia + Australia)
27
Q

Which type of dye is used for a cryptococcal stain?

A

India ink

29
Q

You are the FY1 on the renal team. You have been asked to go and review a patient in the renal assessment unit who has a cough and SOB. The nurse tells you that the patient is desaturating when she walks. A CXR is done.

What do you see? What is the diagnosis?

A

Diffuse bilateral infiltrates with fine reticular interstitial changes = likely PCP

30
Q

Describe management steps (3) for CNS cryptoccal infection

A
  1. Induction => Amphotericin B + Flucytosine (at least 2/52)
  2. Consolidation => High dose fluconazole (at least 8/52)
  3. Maintenance => Low dose fluconazole (at least 1 year)
    - repeat LP for pressure management
    - if mild pulmonary disease; fluconazole alone.
33
Q

What diagnostic investigations (5) would you order in suspected aspergillosis?

A
  1. Imaging - CXR
  2. Sputum/BAL - MC&S, Ag testing
  3. Biopsy - Histology, MC&S
  4. Aspergillus abs - aspergillus precipitan test

5 Galactomannan - to check for disseminated aspergillosis

34
Q

How would you manage (1) aspergillosis?

A

Voriconazole OR amphotericine B (at least 6/52)

  • duration depends on host/radiological/mycological factors
35
Q

Pneumocystis jiroveci - describe it’s cell wall

A

lacks ergosterol

36
Q

Diagnosis?

How would you treat it (2 steps)?

A
  1. Mucormycosis - will confirm with tissue biopsy
  2. Mx:
    - ambisome/posaconazole
    - debridement
37
Q

Pneumocystis jiroveci - route of transmission

A

Airborne route therefore commonly presents as pneumonia

* extra-pulmonry disease is RARE

38
Q

RFs (1) for Pneumocystis jiroveci pneumonia

A

Any aetiology leading to immunodeficiency (drugs, infection, genetics, enviromental)

40
Q

What is the diagnosis? most common causative agents?

A

onchomycosis - often caused by dermatophytes

41
Q

Describe the diagnostic tests (3) for pneumocystic jiroveci (PCP)?

A

Serum/Sputum/BAL/biopsy:

  1. Microscopy
  2. PCR
  3. Beta-D-glucan
42
Q

What is the management (2) of PCP?

A
  1. High dose co-trimoxazole (2-3/52)
  2. Steroids if hypoxic
43
Q

Why might antifungal targeting the cell membrane not work in PCP?

A

Lacks ergosterol in cell wall

therefore can’t used azoles

44
Q

How does mucormycoses spread (2)?

A
  1. Inoculation via inhalationo of spores
  2. Primary cutaneous inoculation
45
Q

Mucormycoses - high risk groups (2)?

A
  1. Immunosuppressed
  2. Diabetics
46
Q

Describe rhinocerebral to CNS infection of mucormycoses

A

Cellulitis of the orbit + face => progresses with discharge of black pus from the palate and nose => Retro-orbital expansion produces proptosis, chemosis, ophthalmoplegias, blindness.

Can spread back to brain, causing decreasing levels of consciousness

48
Q

What are dermatophytes? How do they spread?

A

A group of moulds capable of invadind DEAD keratin of skin, hair, nails

spread via contact with desquamated skin scales

49
Q

RFs (3) for dermatophyte infections

A
  1. Moisture
  2. Deficiencies in cell-mediated immunity
  3. Genetic predisposition
50
Q

Name the dermatophyte infection of each site

  1. Foot
  2. Scalp
  3. Groin
  4. Abdomen
A
  1. Foot = tinea pedis
  2. Scalp = tinea capitis
  3. Groin = tinea cruris
  4. Abdomen = tinea corporis
52
Q

Treatment (2) of dermatophytic infections (nail/skin)

A
  1. Topical => clotrimazole,, ketoconazole
  2. Oral => itraconazole
53
Q

Name the most common associated side effect of each antifungal class

  • Azoles
  • Polyenes
  • Echinocandins
  • Pyrimidine analogues
A
  • Azoles = abnormal LFTs
  • Polyenes = nephrotoxicity
  • Echinocandins = relatively innocuous
  • Pyrimidine analogues = blood disorders
54
Q

Name 2 groups of antifungals that target cell membrane

A
  1. Azoles (ketoconazole, itraconazole, fluconazole) = inhibit ergosterol synthesis
  2. Polyenes (amphotericin B, nystatin) = punch holes in cell membrane
55
Q

Name 1 antifungal class that acts against cell wall and its MOA

A

Echinocandins - inhibits B(1,3)-D-glucan synthase - loss of cell wall glucan => osmotic fragility

56
Q

Which of the following are echinocandins effective against?

  • Yeast
  • Mould
  • Cryptoccocus

Which body site can they NOT penetrate?

A
  • Yeast = yes
  • Mould = no
  • Crytpo = no

Cannot get into urine

57
Q

Name 1 antifungal that work by inhibiting DNA/RNA synthesis?

A
  1. Pyrimidine analogues (i.e. Flucytosine)

Pathology by week (70 decks)

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