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Microbiology > Fungal Infection > Flashcards

Fungal Infection Flashcards

1
Q

What type of microorganism are fungi?

A

Eukaryotes - have similar metabolism to humans

Have several chromosomes and massive, complex genome

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2
Q

What are the two phyla of fungi?

A
  • Basidiomycota

- Ascomycota

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3
Q

How many serious fungal infections are there and what % of them as ascomycetes?

A

150

90% of all fungal infections

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4
Q

Cryptococcal meningitis

A

Out of the basidiomycetes, Cryptococcus neoformans and Cryptococcus gatii cause the largest burden of disease - CRYPTOCOCCAL MENINGITIS
Cryptococcus can get into the brain (a sugar rich environment) and cause meningitis

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5
Q

How do fungi digest their food?

A

Extracellularly
They produce hydrolytic enzymes which are pumped out into the environment.
This means that they are saphrophytes.

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6
Q

What are fungal spores?

A

They are produced by fungi in large amounts and are dispersed over large distances.

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7
Q

What are the three main types of illnesses caused by fungi?

A
  • allergies
  • mycotoxicoses
  • mycoses
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8
Q

How can the level of infection be classified based on tissue?

A
  • superficial
  • subcutaneous
  • systemic
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9
Q

What are some examples of allergies caused by inhaling fungal spores?

A
  • Rhinitis
  • Dermatitis
  • Asthma
  • Allergic Broncho-Pulmonary Aspergillosis (ABPA)
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10
Q

What is mycotoxicoses?

A

A toxic reaction due to the ingestion/inhalation of toxins produced by fungi.

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11
Q

What are mycotoxins?

A

Secondary metabolites of moulds that exert toxic effects on animals and humans

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12
Q

What are the symptoms and treatment of mycotoxicoses?

A

Symptoms:

  • Breathing problems
  • Dizziness
  • Severe vomiting
  • Diarrhoea
  • Dehydration
  • Hepatic and renal failure 6 days later

Treatment:

  • Gastric Lavage - wash out the toxins
  • Liver transplant
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13
Q

Aflatoxin

A
  • It is produced by Aspergillus flavus - most carcinogenic natural compound known.
  • Contaminates grain
  • If you get aflatoxin poisoning and you have liver damage from hepatitis B then you are at particular risk of cancer
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14
Q

What is mycoses?

A

Disease caused by fungi which is classified by the level of tissue affected (superficial, cutaneous, subcutaneous, systemic)

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15
Q

What is superficial mycoses?

A
  • Affecting skin or hair

- No living tissue is invaded no cellular response from host

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16
Q

Give examples of superficial mycoses infections

A
  • black piedra (affects scalp hair)
  • white piedra (affects facial, axillary and pubic hair)
  • dandruff
  • tinea nigra (affects skin)
17
Q

What is cutaneous mycoses?

A
  • keratinases made which are capable of hydrolysing keratin
  • Inflammation is caused by host response to metabolic by-products
  • AKA dermatophytocis and dermatomycosis
  • given the name tinea (worms)
18
Q

Give examples of dermatophytes (cause cutaneous mycoses)

A

Trychopyton and Microsporum

19
Q

Give examples of cutaneous infections

A

Tinea Capitis (scalp ringworm)- most common paediatric dermatophyte infection

Tinea pedis (soles of feet and in between toes)

Tinea corporis (ring worm)

20
Q

What is subcutaenous mycoses?

A

Chronic, localised infections of the skin and subcutaneous tissue following traumatic implantations of the aetilogic agent

21
Q

What is mycetoma?

A

Chronic infection of the skin, subcutaneous tissue and sometimes bone, characterised by discharging sinuses filled with organisms

22
Q

Deep/systemic mycoses

A

primary (infect in normal host):

  • coccidiodes immitis
  • histoplasma capsulatum

oppurtunistic:

  • candida
  • fusarium
  • aspergillus
23
Q

In which situations are fungal infections a big problem?

A
  • transplants (aspergillosis)

- high mortality rate for systemic mycoses

24
Q

Candida

A
  • oppurtunistic
  • normally in GIT, UGT
  • in immunocompromised can cause superficial, mucosal and systemic infection

superficial candida:

  • mouth, throat, skin, scalp, vagina, fingers, nails, bronchi and lungs
  • usually due to impaired epithelial barrier function
  • most common in the new born and elderly

mucosal candida:

  • occurs in newborn and elderly
  • occurs in 3 forms in people with HIV - oropharyngeal, oesophageal, vulvovaginal

systemic candida:

  • not in healthy people
  • high mortality rate
  • main risk factors- chemo, catheters, gut related surgery
25
Q

Invasive aspergillosis

A

Emerged as the major clinical problem of common mycology - 60,000 worldwide yearly

26
Q

How can fungal infections be diagnosed?

A
  • Sample Acquisition:
    Skin, sputum, bronchoalveolar lavage, blood, vaginal swab/smear, spinal fluid, tissue biopsy
  • Microscopy
    Need to have a well established fungal infection to be able to see it down the microscope
  • Culture
    Once it has been identified under the microscope, it can be cultured, allows susceptibility testing
- Non-Culture Methods 
Antibody and Antigen-based assays can be used to detect fungal polysaccharides: 
Glucan 
Mannan 
Endolase 
Proteinase
27
Q

What are the three main targets for antifungal therapy?

A
  • cell membrane: ergosterol instead of cholesterol
  • DNA synthesis
  • cell wall: not in humans
28
Q

Cell membrane antifungals

A
  • inhibit ergosterol synthesis
  • azole is main drug group
  • examples of azoles are Itraconazole and Fluconazole
29
Q

Fungal RNA/DNA synthesis inhibitors

A
  • pyrimidine analogues usually used

- Flucytosine is commonly used for Cryptococcus

30
Q

Cell wall antifungals

A
  • inhibit the cell wall specific to fungus
  • major components of cell wall are glucans and chitin
  • Echinocandins are a group of drugs that do this
  • Caspofungin is the drug example - works by non specific inhibition of beta 1,3 glucan synthase
31
Q

What are the three types of candida infections that can occur people who are immunocompromised?

A

mucosal
systemic
superficial

Microbiology (8 decks)

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