Infectious Agents Flashcards Preview

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Flashcards in Infectious Agents Deck (31)
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1
Q

How are microbes visualised?

A

Bacteria, fungi, protozoa, and helminths
- can be seen using light microscope (x400 to x 1000)

Viruses seen via EM x40,000

2
Q

How does bacterial growth occur?

A

Via binary fission with each doubling taking 20-30 mins at optimum of 35-37 ℃

3
Q

Describe the structure of a virus

A

20-300um
DNA/RNA genome
Linear, segmented, single or dsGenomes of varying sizes 9kb - 300kb
Have nucleocapsid (protein core)
No cytoplasm
(non)Enveloped
May have host component on viral membrane

4
Q

What is the Linnean classification system?

A
Domain 
Kingdom 
Phylum 
Class 
Order 
Family 
Genus 
Species
5
Q

What is required for bacterial growth?

A
  • Carbon, water, nitrogen
  • nutrients & minerals
  • correct osmotic pressure
  • correct pH
  • correct Temperature
  • correct atmosphere
6
Q

Describe the key features of protozoa

A
  • single cells
  • 5-300 um
  • single / multiple nuclei
  • trophozites, cysts, and othe rmorphocytes have complex
    life cycles
  • Haploid DNA
  • Morphology varies throughout life cycle
  • can have flagella
7
Q

How are different virus’ classified?

A

Viruses can be classified based on their protein nucleocapsid structure

  • helical
  • cubic
  • complex arrangement
8
Q

Describe the Ebola virus

A

Enveloped RNA virus with a very complex nucleocapsid part of the filoviridae family

9
Q

What criteria is used to classify pathogenic organism?

A
  • Structural, functional and metabolic observations

- Molecule and genetic / genome analysis

10
Q

What are helminths?

A

Multicellular parasitic worms

11
Q

Describe the key features of Bacteria

A
  • 1/1000th of a mm
  • 0.5 - 3um
  • Prokaryotic
  • Haploid DNA
  • Circular genome
  • no nucleus
  • no mitochondria
  • undergoes binary fission
  • usually has rigid cell wall outside cytoplasmic membrane
12
Q

What is the significance of pathogenic organism classification?

A

Identification is essential to understand the (micro)biology, evolution & phylogenetics, pathogenesis of infectious diseases, life cycles, diagnosis, effective treatment and public health control of infectious diseases

13
Q

What are parasites?

A

Organisms that live in an organism of another species (host) and benefits by deriving nutrients at the other’s expense

14
Q

What is the difference in the movement of motile and non motile bacteria?

A

Motile bacteria with flagella move rapidly

Non motile bacteria move ‘on the spot’

15
Q

Compare and contrast prokaryotes and eukaryotes

A

Prokaryotes e.g. bacteria

  • No nucleus
  • no mitochondria
  • mainly circular DNA

Eukaryotes

  • chromosomes
  • nucleus
  • membrane bound organelles
16
Q

Describe structural features of helminths

A
  • Have different morphologies and sizes at different
    stages of their life cycles
  • Can be microscopic or visible to the eye
17
Q

What technique is used to distinguish between bacterial species?

A

Gram staining bacteria
stains include:
- iodine, alcohol, safranin

18
Q

Where do virus’ replicate?

A

Virus’ are obligate intracellular organisms so can only replicate inside host cells

19
Q

What are the biological characteristics of the 4 microbes?

A

All organisms are cells except viruses - don’t have membranes
Cell life cycles, cellular and genome organisation
Parasites are multi-cellular

20
Q

Name 3 examples of Fungi / their infections caused

A

Superficial mucosa
- skin, nail, hair & mucosal membranes (dermatophytes) or
thrush

Cutaneous - Tanea (ringworm)

Systemic muycoses e.g. histoplasmosis

21
Q

What are the 3 groups of helminths?

A

Cestode - tapeworms e.g. taenia, saginata (beef
tapeworm)

Trematode - flatworms or flukes including: schistoma
haematobium
-> cause of bilharzia / schistosomiasis

Nematodes - roundworms e.g. Ascaris lumbricoides

22
Q

Compare the 4 types of microbes with each other

A

Parasites are more complex than viruses
Viruses are tiny in comparison to bacteria and protozoa
Bacteria are x10 or x100 smaller compared to animal / plant cells
Light microscopes used to see bacteria
Electron microscope used to see viruses

23
Q

Outline the life cycle of a virus

A
  1. Attachment - virus attaches to target cell
  2. Penetration - cell engulfs virus via endocytosis
  3. Uncoating - viral contents released
  4. Biosynthesis - viral RNA enters nucleus, replicated by
    viral RNA Pol
  5. Assembly - New phage particles made and released
    into extracellular fluid - cell continues new virus
    production
24
Q

Describe the structure of the Influenza Virus

A

Influenza virus is an enveloped virus with surface haemaglutinin

25
Q

What is fungi classification based on?

A

Fungi classification is complex and based on morphology, reproduction mode (Sexual/asexual) and disease caused
It’s easier to consider fungi by type of infection

26
Q

What are the 4 major microbe types?

A

Viruses
Bacteria
Fungi
Parasites

27
Q

Describe the structural features of fungi

A
  • over 2um
  • eukaryotic
  • can be single or multi-cellular
  • Haploid or diploid
  • single or multiple nuclei
  • rigid chitinous cell wall
28
Q

Describe the features of Adenovirus

A

Adenovirus is an example of non-enveloped DNA virus usually associated with conjunctivitis

29
Q

Give examples of the different structures of fungi

A

Yeast
spheroid single cells budding and dividing

Filamentous forms / moulds
hyphae
multi-nucleating branching hyphae form mycelium

30
Q

Describe anaerobic bacteria growth and visualisation

A

anaerobic bacteria only grow in absence of O2

Gram +ve, rod like spores forming

31
Q

How are microbes classified?

A

Based on:

  • size
  • biological complexity
  • life cycles
  • prokaryotes / eukaryotes
  • haploid / diploid
  • genomes and genetics