Lecture 9- Fungal Infections Flashcards

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1
Q

What is the structure of the fungal genome?

A

Eukaryotic, contain chromosomes

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2
Q

What are the two groups of fungi?

A

Ascomycota (majority are this)

Basidiomycota (cause cryptococcal meningitis)

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3
Q

How do fungi acquire their nutrients? what is the term for this?

A
  • secrete hydrolytic enzymes
  • break down polymers to be absorbed
  • THEY ARE SAPROPHYTES
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4
Q

How do fungi replicate?

A
  • produce larger numbers of spores

- dispersed over large distances

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5
Q

What are the three types of illness caused by fungal diseases?

A

1) Allergies
2) Mycotoxicoses
3) Mycoses

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6
Q

What causes fungal allergies? Give some examples of fungal allergies?

A

Inhalation/contact with fungal spores

  • rhinitis
  • dermatitis
  • asthma
  • allergic broncho-pulmonary aspergillosis (ABPA)
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7
Q

What causes Mycotoxicosis?

A

A toxic reaction caused by ingestion or inhalation of a mycotoxin.

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8
Q

What are Mycotoxins?

A

Mycotoxins are secondary metabolites of moulds that exert toxic effects on animals and humans

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9
Q

What are the symptoms of mycotoxicosis?

A

Breathing problems, dizziness, severe vomitting, diahorrea, dehydration, hepatic and renal failure 6 days later

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10
Q

What is the therapy for Mycotoxicosis?

A
  • Gastric lavage and charcoal (for adsorption)

- Liver transplant

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11
Q

What is aflatoxin produced by? what does it cause

A

Aspergillus flavus ( one of the most natural carcinogens)–> HCC especially in people with HepB induced liver damage

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12
Q

Where is aflatoxin found?

A

It contaminates grain

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13
Q

What are mycoses?

A

A disease classified by the level of tissue affected- superficial, cutaneous, subcutaneous and systemic

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14
Q

What is infected in superficial mycoses? What are its symptoms?

A
  • Skin and hair shaft
  • no living tissue= no cellular response from the host
  • increased oleic acid levels –> inflammation of stratum corneum & dandruff
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15
Q

What are cutaneous mycoses?

A
  • Produce EC keratinases which hydrolyse keratin
  • causes inflammation because of metabolic by-products
    = Dermatomycoses
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16
Q

Give some examples of dermatomycoses

A
  • Tinea capitis: most common paediatric dermatophyte infection
  • T. pedis: athlete’s foot = most common dermatophyte
  • T. corporis: (aka ringworm) treated by anti fungal cream/ oral

Tinea= worm because initially thought to be worm-like parasites

17
Q

What are subcutaneous mycoses?

A

Chronic, localised infections of the skin and subcutaneous tissue after traumatic implantation of etiological agent.

18
Q

What are the two different types of systemic mycoses?

A

1) Primary= able to establish infection in a normal healthy host
2) Opportunistic= require a compromised host in order to establish infection

19
Q

Give an example of a superficial mycoses

A

Aspergillosis - high MR

20
Q

Give an example of a superficial mycosis and the parts of the body it infects for different patients

A

Candida albicans- an opportunistic commensal
HEALTHY- GI tract, GU tract and skin
IMMUNOCOMPROMISED-
- superficial: mouth, throat, skin because of impaired epithelial barrier function (newborn and elderly)
- mucosal: oropharyngeal, oesophageal, vulvovaginal in people with HIV. New born + elderly
- systemic infections: High MR

21
Q

What are the risk factors for systemic candida infections?

A

Chemo
Gut related surgery
Catheters

22
Q

What are the 4 methods of diagnosing fungal infections?

A

1) Sample acquisition
2) Microscopy
3) Culture
4) Non- culture methods

23
Q

Where might samples be acquired from?

A
  • skin
  • sputum
  • lavage
  • blood
  • vag swab/ smear
  • spinal fluid
  • tissue biopsy
24
Q

What are the pros and cons of diagnosing infections through microscopy?

A

PROS: rapid, cheap
CONS: need to have well established fungal infection to be able to see down the microscope

25
Q

What are the disadvantages of culture methods?

A
  • slow
  • prone to contamination
  • retires skilled sample collection methods
  • susceptibility testing (seeing which antibiotic kill it)
26
Q

What are the targets for anti fungal therapy?

A

1) Cell membrane (use ergosterol instead of cholesterol)
2) DNA synthesis
3) Cell wall

27
Q

Name two groups of cell membrane anti-fungals and describe how they work

A
  • Polyene antibiotic
  • Azole antifungals
  • inhibit synthesis of ergosterol in cell membrane
28
Q

Which drugs are used for DNA synthesis inhibition?

A

Pyramidine analogues
- Flucytosine
Use combo therapy with azoles

29
Q

What are the main drugs targeting the fungal cell wall? How does it work?

A

Echinocandins
- Caspofungin
Inhibits B-glucan synthase

30
Q

What are fungal cell walls made out of?

A

Glucans and Chitin