Fungi Flashcards

1
Q

What is a fungi?

A
  • Chemo-organotrophic eukaryote
  • Lack chlorophyll, means it doesn’t synthesise
  • Produce spores
  • Cell wall absorbs nutrients, also contains polysaccharides
  • Membrane contains ergosterol
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2
Q

Chemotroph

A

Bond energy is released from a chemical compound

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3
Q

Organotroph

A

Organic compounds are used as electron donor

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4
Q

Structure of fungi

A
  • Spores
  • Hypha
  • Clamp connection
  • Septa
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5
Q

Spores

A
  • Conidiospore with chains of conidia are where the spores are being dispersed of
  • Produced when conditions are less than ideal, conidiophores can form and release spores into the environment
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6
Q

Hypha

A
  • Branch out, filamentous structure

- One or more cells surrounded by tubular cell wall

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7
Q

3 groups in fungal kingdom

A
  • Basidiomycetes
  • Ascomycetes
  • Zygomycetes

All can cause human disease

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8
Q

Basidiomycetes

A
E.g. Cryptococcus species
Sexual spores: basidiospores
Asexual spore: conidium
Examples: mushrooms
Releases basidospores
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9
Q

Ascomycetes

A
E.g. Candida, aspergillus spp.
Sexual spore: ascospore
Asexual spore: conidium
Examples: Neurospora, saccharomyces
Contained within sac
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10
Q

Zygomycetes

A

E.g. rhizopus spp.
Sexual spore: zygospore
Asexual spore: sporangiospore
Examples: Bread moulds

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11
Q

Yeasts

A

Fungi that favour a unicellular habit
Mother cells form bud and when bud becomes same size as mother cell it can split off
e.g. Candida spp. are yeasts

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12
Q

Athlete’s foot

A
  • Epidermophyton, microsporum and Trichophyton spp.
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13
Q

Thrush

A

Candida spp.

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14
Q

Pityriasis vericolor

A

Malasszia spp.

Also form hyphae in infected skin

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15
Q

Tinea

A

Ringworm
Caused by dermatophytes: epidemophyton, microsporum and trichophyston spp. Moulds with a predilection to degrade keratin as a nutrient source
Face - facei, barbae - beardy area, coporis - tummy, cruris - pubic area, manum - hand, pedis - feet, unguium - toenails

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16
Q

How can fungi be fatal?

A

Act as an opportunistic pathogen of immunocompromised patients

17
Q

Candida spp. as a fatal disease

A
  • Infect deep organs of patients with various types of immune dysfunction e.g. after abdo surgery, burns etc.
  • Can exist in mucosal membranes and can enter blood after surgery and nd up in non-mucosal organs
18
Q

Aspergillus spp. as a fatal disease

A
  • Infect deep organs of patients undergoing chemotherapy, stem cell transplantation
19
Q

Pathgenecity of fungal infections

A
  • Favourable micro-environments (warm, moist areas) encourage growth of fungi
  • Broad-spectrum antibacterial agents reduce competition for epithelial colonisation sites in gut
  • Immunosuppresion
20
Q

Immunosuppression of host defences examples:

A

Iatrogenic: steroids, chemotherapy, solid-organ transplantation

Disease processes: AIDs, leukaemia, endocrinopathies

21
Q

Candida examples

A
Albicans - Oral
Tropicalis - Vaginal
Glabrate - Skin
Krusei - Nail
Parapsilosis - Oesophageal
Other spp. - UTI and disseminated infections (seriously immunocompromised)
22
Q

Aspergillosis examples

A

Fumigatus - simple asthma
Flavus - asthma with eosinophilia
Other spp. - Aspergilloma, aspergillosis

23
Q

Aspergillosis

A
  • Moulds found in the environment, inhaling conidia all the time
  • Strongly angioinvasive, penetrate walls of blood vessels
  • If immunosuppressed can infect body, hyphae can grow and inseminate blood vessels
  • Very difficult to treat due to membrane-type surround
24
Q

Cryptococcus examples

A

Neoformans - pulmonary cryptococcosis

Gattii - yeasts with a capsule, meningitis as can cross BBB. Disseminated infection for immunocompromised

25
Q

Diagnostic methods

A
  • Direct detection: histopathology, high-res CT scan
  • Growth on selected medium: chlorogenic substrate can break down and show different colours for different strains
  • Detection of circulating fungal antigens
  • Detection of circulating antibodies to fungi
  • PCR for fungal DNA
  • Culture of fungus from normally sterile site
26
Q

Histopathology

A
  • Biopsy, can stain the hyphae
  • Dermatophytes visualised directly in skin scales
  • Direct smear
27
Q

High-res CT scans

A
  • Hepatic Candida infection

- Aspergillosis, can see typical halo around it

28
Q

Factors to consider in fungal treatment

A
  • Spectrum of activity
  • Static or cidal
  • IV or oral
  • Toxicity
  • Resistance
  • Cost