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Lucy Knox - Year 2.5 > 228 - Fungal Disease > Flashcards

228 - Fungal Disease Flashcards

1
Q

What do we call species that feed on dead material?

A

Saprophytes

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2
Q

Can fungi all cause infection?

A

No, 250,000 known but 180 cause mycosis in humans

Most opportunistic

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3
Q

How can a fungus damage you without actually causing an infection?

A

Through ingestion of mycotoxins, or allergy from spores

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4
Q

What investigations are used to make a diagnosis or identify a fungal infection?

A

Sample collected
Macroscopic exam - are there particles, caseous, purulent
Direct microscopic exam + Histology - using variety of stains (KOH, Silver)
Culture
Serology

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5
Q

What is the difference in culture media for fungi?

A

Use SAB agar or mycobiotic agar - they don’t grow on normal agar

Takes 1-3 weeks, in an aerobic 30 degree environment

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6
Q

What is a woods lamp?

A

A UV light test used to identify superficial fungal infections - they will fluoresce.

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7
Q

What is a dermatophytosis?

A

Superficial fungal infection of skin, hair, nail - keratinised tissue

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8
Q

What species of fungus cause dermatophytosis?

A

Trichophyton
Epidermophyton
Microsporum

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9
Q

What are dermatophyte infections otherwise known as?

A

Ringworms

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10
Q

What is the name given to dermatophyte infections in the:

Body
Foot
Goin
Scalp
Hands
Nail
A 
Body - ringworm
Foot - tinea pedis / atheletes foot
Groin - Tinea cruris / jock's itch
Scalp - Tinea Capitis
Hands - Tinea manuum
Nail - Tinea unguium / onchomycosis
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11
Q

How are dermatophytes transmitted?

A

close contact or indirect contact

Need moisture

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12
Q

Describe pityriasis Versicolour

What causes it?

A

A superficial infection of the stratum corneum of skin.

Causes hyperpigmentation or depigmented macules on the trunk or proximal limbs

Malassezia furfur

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13
Q

What causes malassezia furfur to cause an infection rather than just being a commensal?

A

Associated with a change from a yeast growth form to pseudohyphal form

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14
Q

How can you treat pityriasis versicolor?

A

Ketoconazole shampoo

or oral itraconazole / fluconazole

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15
Q

What is superficial candidiasis?

A

An infection of mucous membranes - thrush

Causes soft white plaques in vagina, oral cavity, oesophagus, often following antibiotics

In immunocompromised can cause systemic candidaemia - 30% mortality

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16
Q

What is pneumocystis ?

A

Caused by pneaumocystis jiroveci / carinii

Can cause PCP : pneumonia in compromised hosts (AIDS related disease)

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17
Q

What makes pneumocystosis an interesting fungi?

A

It was originally thought to be a protozoa - as has similar morphology and same drugs work.

There is no ergosterol in their membranes (seen in other fungi) and can’t grow on fungi media

BUT has fungi ultrastructure and it’s RNA is fungal

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18
Q

What is cyrptococcosis?

A

Fungal meningitis

Caused by cryptococcus neoformans

Associated with pigeon droppings worldwide, transmitted by inhalation of fungal aerosols

Begins with an asymptomatic resp infection then gets into CNS

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19
Q

What is histoplasmosis?

A

Pneumonia from bat or bird droppings containing fungi

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20
Q

What is madura foot?

A

A fungal infection from standing on a thorn in the tropics - get painless swelling then lytic lesion on the bone - needing amputation

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21
Q

What is meant by a fungus that is a ‘true pathogen’?

A

When close contact will usually cause infection - which is often asymptomatic

eg. via inhilation of fungal spores

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22
Q

What are some examples of fungal true pathogens?

A

Histoplasmosis - bats/birds, S+N america and W africa

Coccidodomycosis - Cslifornia/W america - Pneumonia

Blastomycosis - N america - Lung, forms blastomyces sand skin lesions

Paracoccidodomycosis - S america - miliary lesions + pneumonia

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23
Q

Where is aspergillus fungi found?

A

In soil and organic matter

Globally

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24
Q

How is aspergillus transmitted?

A

Inhalation to Resp tract

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25
Q

What occurs when you have heavy exposure of aspergillus in a normal patient?

A

Hypersensitivity pneumotitis

A combo of type 3 (immune complex) and type 4 (cell mediated) hypersensitivity

26
Q

What symptoms do you get with a hypersensitivity pneumonitis caused by aspergillus?

A 
Dyspnoea
Cough
Fever
4-6 hours after exposure
Stops when away from exposure
27
Q

Name some examples of hypersensitivity pneumonitis caused by aspergillus or people who get it?

A 
Pigeon fanciers lung
Farmers
Humidifyer fever
Brewers/malt workers
Cheese workers
28
Q

What investigative findings are seen with hypersensitivity pneumonitis caused by aspergillus?

A

Fine crackles at end of inspiration
CXR - diffuse reticulo-nodular shaddowing
CT - Bilateral consolidation and air trapping
Restrictive lung function tests

29
Q

How can you treat hypersensitivity pneumonitis caused by aspergillus?

A

Prevent exposure

Immunosuppression to reduce T cell response

30
Q

What happens when a pt with Asthma or Cystic fibrosis is expsed to a low dose of aspergillus?

A

ABPA - Allergic Bronchopulmonary Aspergillosis

  • colonisation of the mucous plugs found in these pts, get a thype 3 + 4 hypersensitivity reaction to them
31
Q

What are the symptoms of ABPA?

A 
Fever
Cough
Dyspnoea
Asthma worsening
Coughing up casts
32
Q

How can you diagnose ABPA?

A

Hypae in sputum
+ve skin test
Bloods: Eosinophilia, increased IgE, +ve antibodies
BAL - broncho-alveolar lavage - +ve.

33
Q

How can you treat ABPA?

A 
Long term antifungals
Oral steroids to reduce T cell response
Manage asthma
Physio
? Bronchoscopy to remove plugs if CXR shows collapse
34
Q

What happens when a pt with pre-existing cavitating lung disease is exposed to a low dose of aspergillus?

A

A mycetoma forms - a fungus ball

There is not real invasion of tissue, just the cavities (eg. TB, brochiectasis)

35
Q

What symptoms or complications can you get with a mycetoma caused by aspergillus invasion?

A

Haemoptysis - fungi releases oxalic acid which erodes vessels

Often asymptomatic or weight loss, lethergy, heamoptysis

36
Q

What does the histology of a mycetoma caused by aspergillus show?

A

Pink necrotic center
Active hypae at rim - detected in sputum culture
Air in the cavity - as aerobic

37
Q

How can you manage a mycetoma caused by aspergillus?

A

Monitor and observe?
Surgical resection?
Antifungals don’t work as can’t penetrate it

38
Q

If an immunocompromised pt is exposed to aspergillosis what can occur?

What is seen on CXR?

A

Get invasive aspergillosis

  • inhale it, causes invasion of blood vessels and tissues within and outside the lung
  • See multiple focal opacities in CXR - with halo sign due to blood film around consolidations.
  • Hypae also block vessels so get multiple lung infacts
39
Q

What symptoms are seen in invasive aspergillosis?

A

Gravely ill

Rapid consolidation and necrosis and cavitation in lung

40
Q

How can you treat invasive aspergillosis?

A

IV anti-fungals - amphtericin + flucytosine

41
Q

What is the link between aspergillus and cancer?

A

Aflatoxin produced by aspergillus grows on mouldy peanuts - causes HCC - hepatocellular carcinoma

Rare in UK but more in Asia

42
Q

What targets do antifungals work on?

A

Things we don’t also have

  • Ergosterol in plasma membrane
  • Proteins in cell walls
43
Q

What are 3 broad ways that antifungals work by?

A

Inhibit membrane synthesis

Inhibit membrane function

Inhibit nucleic acid synthesis and mitosis

44
Q

What are three classes of antifungal that inhibit membrane synthesis?

A

Azoles (block chtochrome p450 - interfeers with ergosterol - toxic metabolites build up - inhibits growth and increases membrane permeability)

Echinocandins (inhibit 1,3 B-glucan synthase - less glycan inc ell wall - weak)

Allylamines (inhibit squalene epoxidase so inhibits ergosterol synthesis)

45
Q

Give examples of some Azole antifungals

A 
Ketoconazole
Clotrimazole
Fluconazole
Intraconasole
Voriconazole
46
Q

What antifungal is good for thrush?

A

Clotrimazole or nystatin (and lots of others)

47
Q

What antifungal is good for tinea barbis?

A

Oral fluconazole (and lots of others)

48
Q

What antifungal can you use for severe tinea pedis or onychomycosis?

A

Oral terbinafine

49
Q

What is tinea incognito?

A

Tinea whose appearance has been altered by inappropriate treatment, eg. topical steroid cream

50
Q

What is an example of an echinocandin antifungal?

A

Caspofungin - IV, needs a loading dose

  • good for aspergillus and candida
51
Q

What is an example of an allylamine antifungal?

A

Terbinaine - topical or oral
Good for dermatophytes

It is lipophilic so concentrates in skin or adipose tissue

(S/e: allergic skin reaction, rarely liver toxicity)

52
Q

Name two polyene antifungals (inhibit membrane function)

A

Amphotericin (oral but low GI absoption. Causes pores to form in fungus - cations leak - damage)

Nystatin (topical - superficial candida)

53
Q

Name one antifungal that inhibits nucleic acid synthesis

A

Flucytosine - used in combos to reduce resistance

54
Q

Name one antifungal that inhibits nucleic acid synthesis and mitosis

A

Griseofulvin - interacts with microtubules

been superseded mostly now, just to be used in dermatophyte infections

55
Q

What are the 2 ways that a fungus can grow?

A

Yeast - unicellular, budding

Filamentous - multicellular, growth by hyphae, reproduce by spores

56
Q

What extra growth forms can fungi grow as?

A

Yeast - can switch to pseudohyphae - dimorphic growth, grow but the buds don’t fully separate - often associated with commensal becoming pathogenic - candida, malassezie furfur

Filamentous - can switch to yeast-like - some fungi are filamentous in the environment but change to yeast like when they invade the body, eg. aspergillus, dermatophytes.

57
Q

Treatment for: Vulvovaginal candidiasis

A

Clotrimazole PV + 1% cream for externalalternative: Fluconazole

58
Q

Treatment for: Fungal nail infection

A

Terbinafine or amorolifine or itraconazole

59
Q

Treatment for: Oral Candidiasis

A

Nystatin oral suspensionor Fluconazole oral

60
Q

Treatment for: Tinea Pedis

A

Clotrimazole

61
Q

Treatment for: Candidaemia (non-CNS)

A

Fluconazole

62
Q

Treatment for: Aspergillosis (non-CNS)

A

Voriconazole

Lucy Knox - Year 2.5 (15 decks)

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