Fungi Flashcards Preview

PoD > Fungi > Flashcards

Flashcards in Fungi Deck (28):
1

What is a fungi?

- Chemo-organotrophic eukaryote
- Lack chlorophyll, means it doesn't synthesise
- Produce spores
- Cell wall absorbs nutrients, also contains polysaccharides
- Membrane contains ergosterol

2

Chemotroph

Bond energy is released from a chemical compound

3

Organotroph

Organic compounds are used as electron donor

4

Structure of fungi

- Spores
- Hypha
- Clamp connection
- Septa

5

Spores

- 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

6

Hypha

- Branch out, filamentous structure
- One or more cells surrounded by tubular cell wall

7

3 groups in fungal kingdom

- Basidiomycetes
- Ascomycetes
- Zygomycetes

All can cause human disease

8

Basidiomycetes

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

9

Ascomycetes

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

10

Zygomycetes

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

11

Yeasts

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

12

Athlete's foot

- Epidermophyton, microsporum and Trichophyton spp.

13

Thrush

Candida spp.

14

Pityriasis vericolor

Malasszia spp.
Also form hyphae in infected skin

15

Tinea

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

16

How can fungi be fatal?

Act as an opportunistic pathogen of immunocompromised patients

17

Candida spp. as a fatal disease

- 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

Aspergillus spp. as a fatal disease

- Infect deep organs of patients undergoing chemotherapy, stem cell transplantation

19

Pathgenecity of fungal infections

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

20

Immunosuppression of host defences examples:

Iatrogenic: steroids, chemotherapy, solid-organ transplantation

Disease processes: AIDs, leukaemia, endocrinopathies

21

Candida examples

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

22

Aspergillosis examples

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

23

Aspergillosis

- 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

Cryptococcus examples

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

25

Diagnostic methods

- 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

Histopathology

- Biopsy, can stain the hyphae
- Dermatophytes visualised directly in skin scales
- Direct smear

27

High-res CT scans

- Hepatic Candida infection
- Aspergillosis, can see typical halo around it

28

Factors to consider in fungal treatment

- Spectrum of activity
- Static or cidal
- IV or oral
- Toxicity
- Resistance
- Cost